Re: [PATCH 2/2] iio: health: Add driver for the TI AFE4404 heart monitor

From: Andrew F. Davis
Date: Tue Nov 10 2015 - 14:20:29 EST

On 11/05/2015 01:09 PM, Jonathan Cameron wrote:
Lars, Hartmut, Peter,

This is becoming a really involved ABI discussion so I'd like some
input on this if any of you have the time.

I'm going to be busy now until at least the weekend...

On 04/11/15 21:17, Andrew F. Davis wrote:
On 11/04/2015 01:40 PM, Jonathan Cameron wrote:
On 02/11/15 20:37, Andrew F. Davis wrote:
On 11/01/2015 02:52 PM, Jonathan Cameron wrote:
On 31/10/15 16:31, Andrew F. Davis wrote:
Add driver for the TI AFE4404 heart rate monitor and pulse oximeter.
This device detects reflected LED light fluctuations and presents an ADC
value to the user space for further signal processing.

Data sheet located here:

Signed-off-by: Andrew F. Davis <afd@xxxxxx>
Hi Andrew,

Good to see this resurface. It's a fascinating little device.

Anyhow, most of the interesting bit in here is unsuprisingly concerned
with the interface. I know we went round a few loops of this before but
it still feels like we haven't worked out to handle it well. I would like
as much input as we can get on this as inevitablly it will have
repercussions outside this driver.

Your approach of hammering out descriptive sysfs attributes is a good
starting point but we need to work towards a formal description that
can be generalised. Whilst there are not many similar devices out there
to this one, I suspect there are a few and more may well show up in

Yeah, I'm working on brining up drivers for them now :)

The escence of my rather roundabout response inline is that I'm suggesting
adding a new channel type to represent light transmission, taking the analogous
case of proximity devices in which we are looking at light reflection.
I've also taken the justification we use for illuminance vs intensity readings
for two sensor ALS sensors as a precident for having compound channels of a different
type to the 'raw' data that feeds them. Hence I propose something along
the lines of:

in_intensityX_raw (raw channel value with the led on)
in_intensityX_ambient_raw (raw channel value with the led off)

I'm not sure, I know it may be too late for a lot of drivers but putting the 'X'
against the 'intensity' works for devices like ADCs/DACs with a simple list
of numeric channels, but for any other device with named channels this will
become very inconsistent, especially when adding modified channels and
differential channels.
Sadly its ABI now so we can't realistically change it. We can extend, we can't
replace (we we can over the course of a lot of years but that's a nightmare).

For example:

The oddity here is that in your case the device in interacting with a stimulus
output. Normally the index reflects an actual sensor. We are kind of bludgeoning
it in. The only equivalently nasty case I know of is touch screens where different
resistances are being connected - from a generic point of view those are a nightmare
as well (as every implementation does it differently).

Yeah, this part really doesn't fit the mold for this subsystem, or
any really, hwmon, input, were also considered, but the plan is still
to attempt to shoehorn it in to this one, so hopefully you can bear with me
on all these oddities :)
Much as it irritates my sense of neat and tidy I guess that if we do end up with
an ABI for this that we don't like later it isn't the end of the world as I doubt
we'll be inundated with hundreds of these sensors.

However, lets keep the naming within reason to how we would naturally extend
the ABI.

Having thought more on these differential channels, do we really need to have
them explicitly as differential channels at all? Perhaps we are better off with




(and it does want to be explicitly meanfiltered and not mean
which would imply the mean over all time)


It's simple, descriptive and almost fits in the current ABI - you could
even blugeon it in easily enough except for the mean filtered case.
In many ways this is your naming proposal after all.

One issue might be that we really only have 4 real channels that become
different things depending on how you setup the device. Matching the
names of the registers is the only way we can label these, as the user
might change their use.


I really can't see any way around it, the channels are just to adjustable.

This will really be true for the afe4300 driver, the part looks to
have about 13 different measurement inputs it can take, all user-select
multiplexed into 1 register/channel. :/

I really don't like the mean filtered case. My suggestion on that
long term is we need to handle 'copies' of channels that are filtered.
These do occur elsewhere.

I'm increasingly coming around to thinking we need additional descriptive
elements in additional attributes to specifically indicate this channel
is a filtered version of this other one. The bit that will bit us
on this is we can't just have a magic _info string that defines
everything as it will break the sysfs rule of one attr to one value
(we stretch this to the limit with the channel description attributes

Hmmm, not sure on this one...

This is the differential of name and an unnamed channel '2', also something
is an average, is it channel '2', is it the whole differential channel? Is
5 this channels id or part of the first differential channel name? Who knows!

The way I would do it is with this more universal format:

Hind sight is a great thing in that the extra _ would have made parsing marginally

And then we just drop trying to deal with modifiers and differential stuff
internally, just let the driver give the channel a name with those. We then
wouldn't need to deal with channels numbers ether, just names.
See my reply to the cover letter thread. You can't pass a name in an event
to userspace and we'd end up string matching all over the place or you end
up not encoding the information currently in the modifier at all.

Perhaps you are right in that it would still have been neater but such is hind sight!

Time for IIO2 :)
hmm. First one was painful enough for me. Also then we have support both
interfaces for a long time... It's really hard to replace an interface with
something else that mostly does the same thing!

The one I wonder about occasionally is similar to what you suggest, but don't
ever having anything other than number (and I'd keep the differential channels.
Then have an extra sysfs attribute that provides the modifier string.

Then I'm not sure it gains us much.
Also note that in the classic ADC case (and there are a whole load more
of those than weird light sensors ;) there are only indexes and differential channels
so it all becomes rather cleaner.


It's also worth noting that whilst we do allow freeform extend_name elements
they are very rarely accepted in drivers as the moment you do that you have
something that standard userspace code won't know what to do with.

struct iio_chan_spec {
enum iio_chan_type type;
const char *name;
unsigned long address;
int scan_index;
struct {
char sign;
u8 realbits;
u8 storagebits;
u8 shift;
u8 repeat;
enum iio_endian endianness;
} scan_type;
const struct iio_event_spec *event_spec;
unsigned int num_event_specs;
const struct iio_chan_spec_ext_info *ext_info;
const char *datasheet_name;
unsigned output:1;

ADCs with lists of numeric channels would then not need to assign to channel
and set indexed, just set name = "3".
And we'd immediately have to string match to do events.


Differential would become:


Again this might be too late to change for some existing drivers, but for
new ones nothing is really stoping this.
There is - abi compliance. We are simply not going to have two different ABIs.
Your use case may involve only drivers that are used with custom userspace code
(afterall this one isn't much use without a load of processing) but the
vast majority of drivers are generic and talk to the same userspace.

Sure, and that's the case I'm mostly interested in, but like you say
below for other devices this is mostly just a discussion of interest.

So whilst this is an interesting discussion, it's effectively an academic
exercise. We have an ABI. What's there is effectively set in stone. New
drivers that do the same thing as existing drivers MUST use the existing

Where we have flexibility is to extend the ABI for devices that haven't
been supported before.

This is where I was hoping for the exception, strange device, strange ABI
Exception -> 'a touch more flexibility than normal' and you can have it.

in_intensitytransmittedX_raw the differential signal which is actually just
measuring the proportion of light that got through the finger or similar.
(other naming suggestions welcome!)

As above, why keep patching the framework, let the drivers set the names,
I would have:

name = "led1-led1_ambient";



which would match the data sheet and match the names of the channels
that these are differencing on ("led1" and "led1_ambient").

Lots more detail inline, but I wanted anyone at a quick glance to know
what we are discussing. Perhaps my suggestion is bonkers so feel free
to pick it to shreds.

The average channels are also unusual to handle. When would a user
want to get both the average and non average channel via the triggered
buffer? I propose that we might handle these generically by treating
the averaging process as a filter and extending the filter interface to
describe it.

Maybe they want one for display and let the hardware do the filtering on
the other? IDK

The end user my not need them both at the same time, but I see no reason
to limit them from using them if the want and keeping them as channels
like in the data sheet to avoid confusion.
Sure. Was just curious ;)

I also do feel that the modularity you have driven for to support your
other part has perhaps come at the expense of some false complexity
(I think there are easier to follow ways of keeping thing modular without
as many duplicate copies of pointers as you pass around here).


p.s. Seemed like a good idea to look at this on a Sunday evening
to avoid some truely terrible TV... Now for the TV I think!

Hope this was more interesting that Sunday evening TV :)
It involved dancing chipmunks. This didn't have to be that interesting ;)

I would guess the majority of people would prefer the dancing chipmunks to
a nice kernel framework ABI discussion ;)
But not the squeaky voices!

.../ABI/testing/sysfs-bus-iio-health-afe4404 | 70 +++
drivers/iio/Kconfig | 1 +
drivers/iio/Makefile | 1 +
drivers/iio/health/Kconfig | 24 +
drivers/iio/health/Makefile | 6 +
drivers/iio/health/afe4404.c | 526 +++++++++++++++++++++
drivers/iio/health/afe440x.h | 159 +++++++
7 files changed, 787 insertions(+)
create mode 100644 Documentation/ABI/testing/sysfs-bus-iio-health-afe4404
create mode 100644 drivers/iio/health/Kconfig
create mode 100644 drivers/iio/health/Makefile
create mode 100644 drivers/iio/health/afe4404.c
create mode 100644 drivers/iio/health/afe440x.h

diff --git a/Documentation/ABI/testing/sysfs-bus-iio-health-afe4404 b/Documentation/ABI/testing/sysfs-bus-iio-health-afe4404
new file mode 100644
index 0000000..c67748b
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-bus-iio-health-afe4404
@@ -0,0 +1,70 @@
+What: /sys/bus/iio/devices/iio:deviceX/out_resistanceY_tia_raw
+ /sys/bus/iio/devices/iio:deviceX/out_capacitanceY_tia_raw
+Date: October 2015
+Contact: Andrew F. Davis <afd@xxxxxx>
+ Get and set the resistance and the capacitance settings for the
+ Transimpedance Amplifier. Y is 1 for Rf1 and Cf1, Y is 2 for
+ Rf2 and Cf2 values.
+ Resistance setting is from 0 -> 7
+ Capcitance setting is from 0 -> 15
These are defined types, so need to be in the relevant defined base units.
I know it is a pain to map real world values directly to the driver units
but if it actually makes sense to expose these to userspace they need to
defined in the same units as every other element of that type is - so
if you don't provide a scale for the 'channels' then it should be
nanofarads and ohms.

I'll see what I can do.

Could be handled as an output channel internaly with and extended_name -
this sort of internally handled value is exactly what
the extended_name stuff is meant to be used to identify.

Not sure if we would gain anything from handling them as actual channels.
Does seem unlikely any code not directly tied to this driver will ever know
what to do with them enough for it to make sense.

These are really controlling a front end analog filter, so another option would
be to use the filter description attributes to handle this. They are however
somewhat 'minimalist' for this case so would need extending. (this will also
get complex if we start describing the average channel as a filtered channel
as well).

Same as above, it probably makes more sense to keep these simple and close
to the data sheet to avoid user having to learn about all this internal
wiring stuff.
Just a small point, but if the exposed interface of a driver to userspace
requires reading the datasheet to understand it, it's not a great starting point.
These are kind of 'magic calibration parameters' so I'm not that bothered.

This part will definitely need a read through of the datasheet before using
anyway :)
pah, manuals are for sensible people!

Good point:)

+What: /sys/bus/iio/devices/iio:deviceX/tia_separate_enable
+Date: October 2015
+Contact: Andrew F. Davis <afd@xxxxxx>
+ Enable or disable separate settings for the TransImpedance
+ Amplifier above, when disabled both values are set by the
+ first channel.
This is an 'interesting' one. Might be cleaner to just have both values exposed
and switch this on and off depending on whether they are equal? That way we
don't need the custom interface.
Perhaps we need a brief description of why one might not want separate control?
(i.e. if we have separate control and set them to the same value, what do we lose?)

If we set them separate by default then users who are following the data sheet
and only writing to the first channel will only be setting the gain of one, and
not both, which is probably what most want.

Also if you want them to be the same and change one first it will cause them to
be out of step until the other is set, might cause problems when setting them
while streaming in data.
Would it ever make sense to set them like whilst streaming? I've no idea!
I'm just keen to keep custom ABI to a minimum.

+What: /sys/bus/iio/devices/iio:deviceX/out_current_ledY_raw
+Date: October 2015
+Contact: Andrew F. Davis <afd@xxxxxx>
+ Get and set the LED current for the specified LED.
+ Y is the specific LED number.
+ Values range from 0 -> 63. Current is calculated by
+ current = value * 0.8mA

Existence of this attribute is fine, but you need to do the relevant
handling to allow it to be a standard current channel. You can't have the
mysterious * 0.8mA. Also it should be called out_currentX_led_raw
(so led is an extended name) IIRC we do this for some proximity sensors.

Isn't this the case for raw? I figured scaled was for when we want the driver
to do the unit conversions for us?
You can do that, but then you need to provide
out_current_ledY_scale to specify what the scale is. If you do, then oops
I missed it.

This way might be easier, I'll see which one works best.

As for naming same as above.

+What: /sys/bus/iio/devices/iio:deviceX/in_intensity_ledY_raw
+ /sys/bus/iio/devices/iio:deviceX/in_intensity_ledY_ambient_raw
+Date: October 2015
+Contact: Andrew F. Davis <afd@xxxxxx>
+ Get measured values from the ADC for these stages. Y is the
+ specific LED number. The values are expressed in 24-bit twos
+ complement for the specified LEDs.
These are getting a little bit 'clunky' in naming. Could map them back to
the simpler

in_intensityX_raw and in_intensityX_ambient_raw and rely on the channel index
to associate them with an LED.

As above, I think that would add unnecessary confusion in mapping numbers to names.
The output channel is for 'led1' the input should be for 'led1' not '1_raw' or
This is still nasty as it's not really it's a channel reading an arbitrary combination
of led signal and ambient. Yes the LED bit is for led 1, but there is nothing here indicating
that a fair bit of the signal may well come from elsewhere.

I'm not really sure if that can be avoided?
You could define it as a summed channel rather than a differential one...
(I'm not saying it would be a good idea though ;)


The led version of ambient strikes me as odd to start with given I think the LED
is turned off during that measurement? This is merely to do with when they
occur in the sequence?

What we are really dealing with here is a single photodiode and an led sequencer.
Perhaps we need a modifier that simply means the source is an led driven at the same instance?
(this is the same as for proximity sensors, but there the signal is explicitly proximity).

Yeah, the device is basically one photodiode and one ADC feeding to one of four storage
registers. The sequencer controls which LEDs are on, what buffer to fill, and
when the ADC is sampling from which buffer to which register. This is all user definable
so you can sample one LED twice, or not even sample the ambient light at all if you

This I why I would like to keep the input names locked to the data sheet, they are named
based on the name of the sequencer control that fills them. Abstracting this away would
add endless confusion.

Maybe, we should be treating these as a different type entirely? They are measuring light
levels, but in common with proximity sensors the 'interesting' bit is what is effecting
those levels. Perhaps a new type would make sense.
How about:


This makes a mess of the differential channels however, as suddenly they are taking the
difference of two signals of different types. Ah well there goes a good plan. I'd neglected
that the transmitted version is the combination of the ambient and the transmitted.

This is irritatingly hard to map onto anything generic.

Exactly, there is no reason to enforce generic names for devices like these.
If there is going to be more than one of them and a common userspace library
then we need to have at least a consistent ABI.

Sure, so then I would just avoid the issue by not adding another type for this,
mostly one off, case.
I'm wondering ultimately how one off it is... What over devices use light transmitted...
Hmm. scanners etc I guess, can't think of other cases with a single led and light sensor
off the top of my head.. Ahah, optical swipe card readers (I'm sure I saw one somewhere
once ;)

Radar, X-ray, if you include all reflected electromagnetic waves as light...

Perhaps the next thing is to think of these a bit like the ALS sensors that use
two sensors to work out what the illuminance is and do it similar to that (somewhat
hiding the relationship). In that case we'd have

in_intensityX_raw (transmitted and ambient - maybe some modifier to indicate this
- like we do for the hideous 'both' modifier for the visible + infrared sensitive
element is some ALSs? - note both seemed sensible at the time, now the name seems
bonkers - oops.)

and the differential would become

In the ALS analogy the transform is often horribly non linear so could
never be represented as a differential channel (unlike here). Maybe
from a userspace interface point of view the best bet here is to not represent
it as a differential channel... Are all such light sensors even linear - here the
assumption is the connected diode is. Perhaps that won't always hold true in future.

(this is my favourite option at the moment)
I still rather like this one ;) In some ways I am wishing we'd defined
light based proximity sensors as
in_intensityreflected_raw as they aren't really measuring proximity at
all (unlike lidar sensors that are).

Still the benefits of hindsight!

The real issue is trying to use the framework and these modifiers to handle
the naming and function for all these different devices, it's no longer a
framework if it has to be modified and extended for every new device type.
The point is to extend it within the general structure of the framework. Of course
it needs to be extended for each new device type. When we first got an accelerometer
did you expect us to pretend it was an ADC because that's all the framework supported
at the time?

Actually yeah, kinda, it is an ADC under the hood, so expose it to userspace like one,
just give it an extended_name like ["x"|"y"|"z"] and everything else in the framework
could remain the same.

This is measuring something new, hence not unreasonable to extend the ABI to cope with
it. Future devices measuring the same thing will have to use the ABI we define here.

But the *way* it is measuring *is* the same, what the data is measuring is irrelevant
to how the data is passed though the framework.

Why extend the framework for the color of the light something is measuring,
Actually I'd like to extend that particular case and add an explicit description
of the wavelengths it is sensitive to. The problem is these things can be horrible
multiple peak cases so it's not always trivial to do that either ..
or the
direction the accelerometer is pointing, walking/running? These should be just plan
channels and let the driver name them according to what they measure. Adding a new
modifier for every possible measurement is unscalable.
Adding strings is just as unscalable - they have to be documented and form part of
the ABI + we have to test against them etc. So all we end up with is the same
massive table in the test utils. If the info was worth providing it means
something that is useful to userspace and hence will need special handling...

This is already the case to some degree, how they are internally stored doesn't
change what gets exposed to sysfs. This really doesn't matter to much as
it may be to late to change anyway.

Yes, the framework grows over time, and yes it needs to be extended. This is only
natural as new devices turn up that do new things.

Be careful to note that your strings naming the things would be just as much part of
the ABI as any new modifier or channel type.

Not necessarily, if the names match a regualar pattern or are provided to userspace in
a standard way, it wouldn't be any different that any other ABI that has different files
available or returns different values depending on what devices are available.

I agree, so where is the advantage? All you end up with is a massive look up table
of namings. We have that now, just the other way around and deliberately more restrictive
to try and keep life sane fo the userspace libraries.

This will help us to lose the lookup table we need now, the available sysfs names and
their uses can all be read out dynamically from a single common interface.

Note that userspace libraries effectively do this as well. Take a look at say the
Android sensor interfaces. There are predefined enums for the types of sensor etc.

If the framework is not general enough it needs to be extended.

+What: /sys/bus/iio/devices/iio:deviceX/in_intensity_led1-led1_ambient_raw
+ /sys/bus/iio/devices/iio:deviceX/in_intensity_led2-led2_ambient_raw
+Date: October 2015
+Contact: Andrew F. Davis <afd@xxxxxx>
+ Get differential values from the ADC for these stages. The
+ values are expressed in 24-bit twos complement for the
+ specified LEDs.
+What: /sys/bus/iio/devices/iio:deviceX/in_intensity_led1-led1_ambient_mean_raw
+ /sys/bus/iio/devices/iio:deviceX/in_intensity_led2-led2_ambient_mean_raw
+Date: October 2015
+Contact: Andrew F. Davis <afd@xxxxxx>
+ Get average values from the ADC for these stages. The
+ values are expressed in 24-bit twos complement for the
+ specified LEDs.

Oh goody another weird one ;) I note in the current proposal, it's not obvious
that the mean acutally applies to the differential. Another element in favour
of the new channel type option.

We do have a chan info element for average raw that would do the job for the sysfs
attribute. However, as you are pushing this into the buffer, it doesn't work for
us here.

This seems like a big problem with the framework at the moment, we have all these
modifiers and chan_info elements, but they only apply to the sysfs read/writes.
So there is a large disconnect between sysfs channels and buffer channels,
but solvable if we drop the modifiers and just have driver named channels.
I do see where you are coming from. Perhaps if we were starting again we could explore
whether it is possible to overcome the issues that drove us to modifiers in the first

IIO2 doesn't sound so bad anymore ;)
Pah, in most cases IIO works. In a few cases we hit whatever it is with the
relevant big hammer. There are a whole load of things I'd like to extend the
ABI to cover, but only a very rare case where I'd agree throwing it away and
starting again would be the better approach.

I'm not really suggesting such a thing, but the smaller the changes the easier
the existing drivers will be to port over to the new style.

Perhaps we can extend the abi to include your naming suggestion (though I would not
include it in the sysfs attribute names, but rather as an additional field) but
it could only be used in cases where we are defining new ABI, not as a replacement
for existing ABI.

Could work

This is basically a low pass filtered version of the signal, so one option would
be a duplicate channel that has the addition of filter attributes to describe that
the filter applied (similar to the existing low pass filter controls).

The challenge would be making it clear that the channel is infact the same as the
led2 channel but with the filter.

Really not worth the effort obscuring these things, I don't see how we gain anything.

Actually, odd question, but why would someone want both the unfiltered and filtered
versions via the buffered interface?

I don't know, but the device offers it as a channel, so why decide for the customer
what they can and cant do?

+What: /sys/bus/iio/devices/iio:deviceX/out_current_offdac_ledY_raw
+ /sys/bus/iio/devices/iio:deviceX/out_current_offdac_ledY_ambient_raw
+Date: October 2015
+Contact: Andrew F. Davis <afd@xxxxxx>
+ Get and set the offset cancellation DAC setting for these
+ stages.
+ Values range from 0 -> 15
Are these in mA?

Not sure I like the naming here. You could either treat them as explicit output
channels, or (and I'd be tempted to favour this) as calibration offsets for the
in_intensitytransmitted_ channel described above (or maybe the straight intensity
channels - I'm now confused on what is what here!).

Can you imagine how the user will feel if we try to hide all the details with
these names? The data sheet calls them 'offdac_led1' so why hide that.
Because the next datasheet that comes along for a different part might call
them something subtly different then we end up with needing custom userspace
code for each part. If we do that then there is no point in having the devices
in IIO in the first place. The reason all this ABI needs to be considered from
a generic point of view is that we are setting precedence. Naming should not
be defined by what it happened to be called on the particular instance of
the datasheet against which the first driver was defined (and yes we have
had instances of the names changing entirely on datasheets).

The point is to come up with ABI that is generic. That is probably the most
important part of IIO (and the bit we spend most time discussing / arguing about).

This is a calibration offset applied to the incoming signal - arguably by calling
offdac_led1 you are obscuring the useful information to the user which is 'what
is this for?'.

If anything they would be offsets for the in_intensity_ledX_raw channels, but
then I'm not sure how you would handle types, the offset is set with current,
the measured value is in intensity.
The advantage of caliboffset is it's unscaled and the relationship to the output
is deliberately never defined as it's rarely linear - so 'what' it is doesn't
actually matter.

We have these on IMUs for example - they often correspond to something magic
in the analog front end that is not even in the datasheet - though if you are
lucky there is an application note explaining the magic test needed to derive
a value (sometimes read from another register under some particular condition).
Usually they are just burnt in values that no one normally touches.

Hmm, looking back at the data sheet these gains are not for the individual channels,
they change the whole front end gain, so they probably won't work as channel

diff --git a/drivers/iio/Kconfig b/drivers/iio/Kconfig
index 4011eff..53e1892 100644
--- a/drivers/iio/Kconfig
+++ b/drivers/iio/Kconfig
@@ -65,6 +65,7 @@ source "drivers/iio/common/Kconfig"
source "drivers/iio/dac/Kconfig"
source "drivers/iio/frequency/Kconfig"
source "drivers/iio/gyro/Kconfig"
+source "drivers/iio/health/Kconfig"
source "drivers/iio/humidity/Kconfig"
source "drivers/iio/imu/Kconfig"
source "drivers/iio/light/Kconfig"
diff --git a/drivers/iio/Makefile b/drivers/iio/Makefile
index 698afc2..d350cb3 100644
--- a/drivers/iio/Makefile
+++ b/drivers/iio/Makefile
@@ -18,6 +18,7 @@ obj-y += common/
obj-y += dac/
obj-y += gyro/
obj-y += frequency/
+obj-y += health/
obj-y += humidity/
obj-y += imu/
obj-y += light/
diff --git a/drivers/iio/health/Kconfig b/drivers/iio/health/Kconfig
new file mode 100644
index 0000000..f5e5d82
--- /dev/null
+++ b/drivers/iio/health/Kconfig
@@ -0,0 +1,24 @@
+# Health drivers
+# When adding new entries keep the list in alphabetical order
+menu "Health"
+menu "Heart Rate Monitors"
+config AFE4404
+ tristate "TI AFE4404 Heart Rate Monitor"
+ depends on I2C
+ select IIO_BUFFER
+ help
+ Say yes to choose the Texas Instruments AFE4404
+ heart rate monitor and low-cost pulse oximeter.
+ To compile this driver as a module, choose M here: the
+ module will be called afe4404.
diff --git a/drivers/iio/health/Makefile b/drivers/iio/health/Makefile
new file mode 100644
index 0000000..c108c8d
--- /dev/null
+++ b/drivers/iio/health/Makefile
@@ -0,0 +1,6 @@
+# Makefile for IIO Health drivers
+# When adding new entries keep the list in alphabetical order
+obj-$(CONFIG_AFE4404) += afe4404.o
diff --git a/drivers/iio/health/afe4404.c b/drivers/iio/health/afe4404.c
new file mode 100644
index 0000000..af65f30
--- /dev/null
+++ b/drivers/iio/health/afe4404.c
@@ -0,0 +1,526 @@
+ * AFE4404 Heart Rate Monitors and Low-Cost Pulse Oximeters
+ *
+ * Author: Andrew F. Davis <afd@xxxxxx>
+ *
+ * Copyright: (C) 2015 Texas Instruments, Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * General Public License for more details.
+ */
+#include <linux/device.h>
+#include <linux/delay.h>
+#include <linux/err.h>
+#include <linux/interrupt.h>
+#include <linux/i2c.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of_gpio.h>
+#include <linux/regmap.h>
+#include <linux/slab.h>
+#include <linux/sysfs.h>
+#include <linux/regulator/consumer.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
+#include <linux/iio/buffer.h>
+#include <linux/iio/trigger.h>
+#include <linux/iio/triggered_buffer.h>
+#include <linux/iio/trigger_consumer.h>
+#include "afe440x.h"
+#define AFE4404_DRIVER_NAME "afe4404"
+/* AFE4404 registers */

Maybe say 'AFE4404 specific registers' to make it clear
there are others in the header.


+#define AFE4404_TIA_GAIN_SEP 0x20
+#define AFE4404_TIA_GAIN 0x21
+#define AFE4404_PROG_TG_STC 0x34
+#define AFE4404_PROG_TG_ENDC 0x35
+#define AFE4404_LED3LEDSTC 0x36
+#define AFE4404_LED3LEDENDC 0x37
+#define AFE4404_CLKDIV_PRF 0x39
+#define AFE4404_OFFDAC 0x3a
+#define AFE4404_DEC 0x3d
+#define AFE4404_AVG_LED2_ALED2VAL 0x3f
+#define AFE4404_AVG_LED1_ALED1VAL 0x40
+/* AFE4404 GAIN register fields */
Is it worth considering the regmap field stuff? That
way all this could go into the field defintions, and
perhaps then give a cleaner driver?

I tried it here, it didn't really add anything useful in this instance.
Fair enough.

+#define AFE4404_TIA_GAIN_RES_MASK GENMASK(2, 0)
+#define AFE4404_TIA_GAIN_RES_SHIFT 0
+#define AFE4404_TIA_GAIN_CAP_MASK GENMASK(5, 3)
+#define AFE4404_TIA_GAIN_CAP_SHIFT 3
+/* AFE4404 LEDCNTRL register fields */
+#define AFE4404_LEDCNTRL_ILED3_MASK GENMASK(17, 12)
+#define AFE4404_LEDCNTRL_ILED3_SHIFT 12
+/* AFE4404 CONTROL3 register fields */
+/* AFE4404 OFFDAC register current fields */
+#define AFE4404_OFFDAC_CURR_LED2_MASK GENMASK(18, 15)
+#define AFE4404_OFFDAC_CURR_LED2_SHIFT 15
+#define AFE4404_OFFDAC_CURR_AMB1_MASK GENMASK(13, 10)
+#define AFE4404_OFFDAC_CURR_AMB1_SHIFT 10
+/* AFE4404 OFFDAC register polarity fields */
+#define AFE4404_OFFDAC_POL_LED1_MASK BIT(9)
+#define AFE4404_OFFDAC_POL_LED1_SHIFT 9
+#define AFE4404_OFFDAC_POL_LED2_MASK BIT(19)
+#define AFE4404_OFFDAC_POL_LED2_SHIFT 19
+#define AFE4404_OFFDAC_POL_LED3_MASK BIT(4)
+#define AFE4404_OFFDAC_POL_LED3_SHIFT 4
+#define AFE4404_OFFDAC_POL_AMB1_MASK BIT(14)
+#define AFE4404_OFFDAC_POL_AMB1_SHIFT 14
+#define AFE4404_OFFDAC_POL_AMB2_MASK BIT(4)
+#define AFE4404_OFFDAC_POL_AMB2_SHIFT 4
+/* AFE4404 TIA_GAIN_CAP values */
+#define AFE4404_TIA_GAIN_CAP_5_P 0x0
+#define AFE4404_TIA_GAIN_CAP_2_5_P 0x1
+#define AFE4404_TIA_GAIN_CAP_10_P 0x2
+#define AFE4404_TIA_GAIN_CAP_7_5_P 0x3
+#define AFE4404_TIA_GAIN_CAP_20_P 0x4
+#define AFE4404_TIA_GAIN_CAP_17_5_P 0x5
+#define AFE4404_TIA_GAIN_CAP_25_P 0x6
+#define AFE4404_TIA_GAIN_CAP_22_5_P 0x7
I'd be tempted to represent this as a lookup table instead
of this set of defines. This is particular true
in light of the fact the sysfs attribute needs to map them
to standard units. Given that will need to be in nano farads
and these are pico you only need the 'val2 part' and use the
int_plus_micro form. The search will be rather more iritating
as these are in a non obvious order, but such is life.

Hence (I'd use the C99 asignments stuff to make it obvious
that the index is important!)

static const int afe4404_tia_gain_caps_femto_farads[] = {
[0] = 5000,
[1] = 2500,
[2] = 10000,
[3] = 7500,
[4] = 20000,
[5] = 17500,
[6] = 25000,
[7] = 22500 };

If I offered the scaled input to userspace this will probably be
how I do it. Before the defines were only used internally for
setting the default values.

+/* AFE4404 TIA_GAIN_RES values */
+#define AFE4404_TIA_GAIN_RES_500_K 0x0
+#define AFE4404_TIA_GAIN_RES_250_K 0x1
+#define AFE4404_TIA_GAIN_RES_100_K 0x2
+#define AFE4404_TIA_GAIN_RES_50_K 0x3
+#define AFE4404_TIA_GAIN_RES_25_K 0x4
+#define AFE4404_TIA_GAIN_RES_10_K 0x5
+#define AFE4404_TIA_GAIN_RES_1_M 0x6
+#define AFE4404_TIA_GAIN_RES_2_M 0x7

Same as for the capacitances.

+enum afe4404_chan_id {
+static const struct iio_chan_spec afe4404_channels[] = {
+ /* ADC values from the IC */
+ AFE440X_READ_CHAN(ALED1VAL, "led1_ambient", AFE440X_ALED1VAL),
+ AFE440X_READ_CHAN(ALED2VAL, "led2_ambient", AFE440X_ALED2VAL),
+ AFE440X_READ_CHAN(LED1_ALED1VAL, "led1-led1_ambient", AFE440X_LED1_ALED1VAL),
+ AFE440X_READ_CHAN(LED2_ALED2VAL, "led2-led2_ambient", AFE440X_LED2_ALED2VAL),
+ AFE440X_READ_CHAN(AVG_LED1_ALED1VAL, "led1-led1_ambient_mean", AFE4404_AVG_LED1_ALED1VAL),
+ AFE440X_READ_CHAN(AVG_LED2_ALED2VAL, "led2-led2_ambient_mean", AFE4404_AVG_LED2_ALED2VAL),
+static ssize_t afe440x_show_register(struct device *dev,
+ struct device_attribute *attr,
+ char *buf)
+ struct iio_dev *indio_dev = dev_to_iio_dev(dev);
+ struct afe440x_data *afe440x = iio_device_get_drvdata(indio_dev);
+ struct afe440x_reg *afe440x_reg = to_afe440x_reg(attr);
+ int reg_val;
+ int ret;
+ ret = regmap_read(afe440x->regmap, afe440x_reg->reg, &reg_val);
+ if (ret)
+ return ret;
+ reg_val >>= afe440x_reg->shift;
+ reg_val &= afe440x_reg->mask;
+ return scnprintf(buf, PAGE_SIZE, "%u\n", reg_val);
+static ssize_t afe440x_store_register(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t count)
+ struct iio_dev *indio_dev = dev_to_iio_dev(dev);
+ struct afe440x_data *afe440x = iio_device_get_drvdata(indio_dev);
+ struct afe440x_reg *afe440x_reg = to_afe440x_reg(attr);
+ unsigned val;
+ int reg_val;
+ int ret;
+ if (kstrtoint(buf, 0, &val))
+ return -EINVAL;
+ ret = regmap_read(afe440x->regmap, afe440x_reg->reg, &reg_val);
+ if (ret)
+ return ret;
+ reg_val &= ~afe440x_reg->mask;
+ reg_val |= ((val << afe440x_reg->shift) & afe440x_reg->mask);
+ ret = regmap_write(afe440x->regmap, afe440x_reg->reg, reg_val);
+ if (ret)
+ return ret;
+ return count;
+AFE440X_ATTR(tia_separate_enable, AFE4404_TIA_GAIN_SEP, AFE440X_TIAGAIN_ENSEPGAIN);
+AFE440X_ATTR(out_resistance1_tia_raw, AFE4404_TIA_GAIN, AFE4404_TIA_GAIN_RES);
+AFE440X_ATTR(out_capacitance1_tia_raw, AFE4404_TIA_GAIN, AFE4404_TIA_GAIN_CAP);
+AFE440X_ATTR(out_resistance2_tia_raw, AFE4404_TIA_GAIN_SEP, AFE4404_TIA_GAIN_RES);
+AFE440X_ATTR(out_capacitance2_tia_raw, AFE4404_TIA_GAIN_SEP, AFE4404_TIA_GAIN_CAP);
I talk about these above. They look to me like they should either be treated as output
channels or possibly as controls on a filter (which is what they really are)
+AFE440X_ATTR(out_current_offdac_led1_raw, AFE4404_OFFDAC, AFE4404_OFFDAC_CURR_LED1);
+AFE440X_ATTR(out_current_offdac_led2_raw, AFE4404_OFFDAC, AFE4404_OFFDAC_CURR_LED2);
+AFE440X_ATTR(out_current_offdac_led3_raw, AFE4404_OFFDAC, AFE4404_OFFDAC_CURR_LED3);
Again, talked about earlier. These could be treated as calibration offsets (similar to
the ones applied to trim gyros in high end IMUs for example).

This stuff makes me wonder whether we are anywhere near descriptive enough of the analog
front ends to devices we support. Probably not I guess!

As above, I would probably just leave this to the individual part driver's discretion how
the front end controls are named and handled.
This is ABI - hence the first driver set precedence. What these do is not really part specific
so we should work out generic ABI.

Anything in mind other that this?
Just keeping everything as sane as possible and as near to current ABI as possible
is all we can really do here.

+AFE440X_ATTR(out_current_offdac_led1_ambient_raw, AFE4404_OFFDAC, AFE4404_OFFDAC_CURR_AMB1);
+AFE440X_ATTR(out_current_offdac_led2_ambient_raw, AFE4404_OFFDAC, AFE4404_OFFDAC_CURR_AMB2);
+AFE440X_ATTR(out_current_led1_raw, AFE440X_LEDCNTRL, AFE4404_LEDCNTRL_ILED1);
+AFE440X_ATTR(out_current_led2_raw, AFE440X_LEDCNTRL, AFE4404_LEDCNTRL_ILED2);
+AFE440X_ATTR(out_current_led3_raw, AFE440X_LEDCNTRL, AFE4404_LEDCNTRL_ILED3);
We already do this for some proximity sensors - just might be better to represent them
as straight forward output channels. I suppose if we really get into it they
are output intensity channels, but perhaps best to ignore that.

Right, they are not meant to be set very often or steamed to like a DAC channel,
probably best to just leave them as sysfs controls.
They can still be sysfs only and channels.
Just set the scan_index for them to -1.

One advantage of this is that they become accessible to other users within the kernel
(why they'd want to access them I have no idea ;)

This is a part made for user-space processing, I cant imagine the point of a
kernel-space helper for this thing, but I guess you never know.
Agreed - it seems highly unlikely as long as the part is used for
what it was designed for ;) Who knows what delightful other use
someone will come up with!

Never know, you really don't have to hook up just LEDs and a photodiode to
these, with the definable output and input timings you could probably do a lot of
interesting things... But until then I think its safe to assume these cases
can all be handled by user-space.

+static struct attribute *afe4404_attributes[] = {
+ &afe440x_reg_tia_separate_enable.dev_attr.attr,
+ &afe440x_reg_out_resistance1_tia_raw.dev_attr.attr,
+ &afe440x_reg_out_capacitance1_tia_raw.dev_attr.attr,
+ &afe440x_reg_out_resistance2_tia_raw.dev_attr.attr,
+ &afe440x_reg_out_capacitance2_tia_raw.dev_attr.attr,
+ &afe440x_reg_out_current_offdac_led1_raw.dev_attr.attr,
+ &afe440x_reg_out_current_offdac_led2_raw.dev_attr.attr,
+ &afe440x_reg_out_current_offdac_led3_raw.dev_attr.attr,
+ &afe440x_reg_out_current_offdac_led1_ambient_raw.dev_attr.attr,
+ &afe440x_reg_out_current_offdac_led2_ambient_raw.dev_attr.attr,
+ &afe440x_reg_out_current_led1_raw.dev_attr.attr,
+ &afe440x_reg_out_current_led2_raw.dev_attr.attr,
+ &afe440x_reg_out_current_led3_raw.dev_attr.attr,
+static const struct attribute_group afe4404_attribute_group = {
+ .attrs = afe4404_attributes
+static int afe440x_read_raw(struct iio_dev *indio_dev,
+ struct iio_chan_spec const *chan,
+ int *val, int *val2, long mask)
+ struct afe440x_data *afe440x = iio_device_get_drvdata(indio_dev);
+ int ret;
+ ret = regmap_read(afe440x->regmap, chan->address, val);
+ if (ret)
+ return ret;
+ *val2 = 0;
There should be no need to set *val2 as it's never read if the return
is IIO_VAL_INT. Nothing wrong with paranoia however ;)


+ return IIO_VAL_INT;
+static const struct iio_info afe4404_iio_info = {
+ .attrs = &afe4404_attribute_group,
+ .read_raw = afe440x_read_raw,
+ .driver_module = THIS_MODULE,
+static irqreturn_t afe440x_trigger_handler(int irq, void *private)
+ struct iio_poll_func *pf = (struct iio_poll_func *)private;
Shouldn't be any need to explicitly cast when coming from a void *


+ struct iio_dev *indio_dev = pf->indio_dev;
+ struct afe440x_data *afe440x = iio_device_get_drvdata(indio_dev);
+ int ret, bit, reg, i = 0;
+ s32 buffer[10];
So there are 9 channels? Then you need space for the timestamp that needs
to be 8 byte aligned. Hence this needs to be s32 buffer[12].
(iio_push_to_buffers_with_timestamp is rather odd - see the documentation)

Yeah, this is a left over from the AFE4403 that only has 8 channels. Fixed.

+ for_each_set_bit(bit, indio_dev->active_scan_mask,
+ indio_dev->masklength) {
+ reg = afe440x->channels[bit].address;

Why using the version in afe440x (which arguably shouldn't be there)
rather than the one in indio_dev->channels[bit].address?

Ops, forgot that is still accesable in indio_dev. Fixed.

+ ret = regmap_read(afe440x->regmap, reg, &buffer[i++]);
+ if (ret)
+ goto err;
+ }
+ iio_push_to_buffers_with_timestamp(indio_dev, buffer, pf->timestamp);
+ iio_trigger_notify_done(indio_dev->trig);
+ return IRQ_HANDLED;
+static const struct iio_trigger_ops afe440x_trigger_ops = {
+ .owner = THIS_MODULE,
+/* Default timings from data-sheet */
+#define AFE4404_TIMING_PAIRS \
+ { AFE440X_PRPCOUNT, 39999 }, \
+ { AFE440X_LED2LEDSTC, 0 }, \
+ { AFE440X_LED2LEDENDC, 398 }, \
+ { AFE440X_LED2STC, 80 }, \
+ { AFE440X_LED2ENDC, 398 }, \
+ { AFE440X_ADCRSTSTCT0, 5600 }, \
+ { AFE440X_ADCRSTENDCT0, 5606 }, \
+ { AFE440X_LED2CONVST, 5607 }, \
+ { AFE440X_LED2CONVEND, 6066 }, \
+ { AFE4404_LED3LEDSTC, 400 }, \
+ { AFE4404_LED3LEDENDC, 798 }, \
+ { AFE440X_ALED2STC, 480 }, \
+ { AFE440X_ALED2ENDC, 798 }, \
+ { AFE440X_ADCRSTSTCT1, 6068 }, \
+ { AFE440X_ADCRSTENDCT1, 6074 }, \
+ { AFE440X_ALED2CONVST, 6075 }, \
+ { AFE440X_ALED2CONVEND, 6534 }, \
+ { AFE440X_LED1LEDSTC, 800 }, \
+ { AFE440X_LED1LEDENDC, 1198 }, \
+ { AFE440X_LED1STC, 880 }, \
+ { AFE440X_LED1ENDC, 1198 }, \
+ { AFE440X_ADCRSTSTCT2, 6536 }, \
+ { AFE440X_ADCRSTENDCT2, 6542 }, \
+ { AFE440X_LED1CONVST, 6543 }, \
+ { AFE440X_LED1CONVEND, 7003 }, \
+ { AFE440X_ALED1STC, 1280 }, \
+ { AFE440X_ALED1ENDC, 1598 }, \
+ { AFE440X_ADCRSTSTCT3, 7005 }, \
+ { AFE440X_ADCRSTENDCT3, 7011 }, \
+ { AFE440X_ALED1CONVST, 7012 }, \
+ { AFE440X_ALED1CONVEND, 7471 }, \
+ { AFE440X_PDNCYCLESTC, 7671 }, \
+ { AFE440X_PDNCYCLEENDC, 39199 }
+static const struct reg_sequence afe4404_reg_sequences[] = {
+ { AFE4404_TIA_GAIN, AFE4404_TIA_GAIN_RES_50_K },
+ (0x3 << AFE4404_LEDCNTRL_ILED2_SHIFT) |
+ (0x3 << AFE4404_LEDCNTRL_ILED3_SHIFT) },
+static const struct regmap_range afe4404_yes_ranges[] = {
+ regmap_reg_range(AFE440X_LED2VAL, AFE440X_LED1_ALED1VAL),
+ regmap_reg_range(AFE4404_AVG_LED2_ALED2VAL, AFE4404_AVG_LED1_ALED1VAL),
+static const struct regmap_access_table afe4404_volatile_table = {
+ .yes_ranges = afe4404_yes_ranges,
+ .n_yes_ranges = ARRAY_SIZE(afe4404_yes_ranges),
+static const struct regmap_config afe4404_regmap_config = {
+ .reg_bits = 8,
+ .val_bits = 24,
+ .max_register = AFE4404_AVG_LED1_ALED1VAL,
+ .cache_type = REGCACHE_RBTREE,
+ .volatile_table = &afe4404_volatile_table,
+#ifdef CONFIG_OF
+static const struct of_device_id afe4404_of_match[] = {
+ { .compatible = "ti,afe4404", },
+ { /* sentinel */ },
+MODULE_DEVICE_TABLE(of, afe4404_of_match);
+static int afe440x_suspend(struct device *dev)
+ struct afe440x_data *afe440x = dev_get_drvdata(dev);
+ int ret;
+ ret = regmap_update_bits(afe440x->regmap, AFE440X_CONTROL2,
+ if (ret)
+ return ret;
+ ret = regulator_disable(afe440x->regulator);
+ if (ret) {
+ dev_err(dev, "Failed to disable regulator\n");
+ return ret;
+ }
+ return 0;
+static int afe440x_resume(struct device *dev)
+ struct afe440x_data *afe440x = dev_get_drvdata(dev);
+ int ret;
+ ret = regmap_update_bits(afe440x->regmap, AFE440X_CONTROL2,
+ if (ret)
+ return ret;
+ ret = regulator_enable(afe440x->regulator);
+ if (ret) {
+ dev_err(dev, "Failed to enable regulator\n");
+ return ret;
+ }
+ return 0;
+SIMPLE_DEV_PM_OPS(afe440x_pm_ops, afe440x_suspend, afe440x_resume);
+static int afe440x_iio_setup(struct afe440x_data *afe440x)
+ struct iio_dev *indio_dev;
+ int ret;
+ indio_dev = devm_iio_device_alloc(afe440x->dev, 0);
+ if (indio_dev == NULL) {
+ dev_err(afe440x->dev, "Unable to allocate IIO device\n");
+ return -ENOMEM;
+ }
+ iio_device_set_drvdata(indio_dev, afe440x);
+ indio_dev->modes = INDIO_DIRECT_MODE;
+ indio_dev->dev.parent = afe440x->dev;
+ indio_dev->channels = afe440x->channels;
+ indio_dev->num_channels = afe440x->num_channels;
+ indio_dev->name = afe440x->name;
+ indio_dev->info = afe440x->info;
+ if (afe440x->irq > 0) {
+ afe440x->trig = devm_iio_trigger_alloc(afe440x->dev, "%s-dev%d",
+ indio_dev->name,
+ indio_dev->id);
+ if (afe440x->trig == NULL) {
+ dev_err(afe440x->dev, "Unable to allocate IIO trigger\n");
+ return -ENOMEM;
+ }
+ iio_trigger_set_drvdata(afe440x->trig, indio_dev);
+ afe440x->trig->ops = &afe440x_trigger_ops;
+ afe440x->trig->dev.parent = afe440x->dev;
+ ret = iio_trigger_register(afe440x->trig);
+ if (ret) {
+ dev_err(afe440x->dev, "Unable to register IIO trigger\n");
+ return ret;
+ }
+ ret = devm_request_threaded_irq(afe440x->dev, afe440x->irq,
+ iio_trigger_generic_data_rdy_poll,
+ "afe4404", afe440x->trig);
+ if (ret) {
+ dev_err(afe440x->dev, "Unable to request IRQ\n");
+ return ret;
+ }
+ }
+ ret = iio_triggered_buffer_setup(indio_dev, &iio_pollfunc_store_time,
+ &afe440x_trigger_handler, NULL);
+ if (ret) {
+ dev_err(afe440x->dev, "Unable to setup buffer\n");
+ return ret;
+ }
+ ret = devm_iio_device_register(afe440x->dev, indio_dev);
+ if (ret) {
+ dev_err(afe440x->dev, "Unable to register IIO device\n");
+ return ret;
+ }
+ return 0;
+static int afe4404_probe(struct i2c_client *client,
+ const struct i2c_device_id *id)
+ struct afe440x_data *afe440x;
+ int ret;
+ afe440x = devm_kzalloc(&client->dev, sizeof(*afe440x), GFP_KERNEL);
+ if (!afe440x)
+ return -ENOMEM;
Hmm. I guess this more of the stuff from this being a highly modular driver.
Right now that is really hurting the organisation of the code.

You'd be better off just using the devm_iio_device_alloc call to allocate
both your private data and the iio device data. You could then pass the
iio_dev to your iio_setup function if you really want to.
Not bouncing through having copies of everything in your afe440x structure
would also make it a lot cleaner without hurting your modularity substantially.

I can see that you were aiming to completely separate the iio side
from the more generic driver parts, but that division is all a bit blured and
leads to more complex code.

Well the reason for this was that everytime I would fix something or add it in
the afe4404 driver I would have to make the same change in the afe4403, so I
moved all this stuff to a single common file. Only the interface and some IIO
table are different between parts. The division is by device differece, not by
IIO/generic code. I can push the AFE4403 driver if you would like to see how
little code is needed to suport the other device.

+ i2c_set_clientdata(client, afe440x);
+ afe440x->dev = &client->dev;
+ afe440x->irq = client->irq;
+ afe440x->regmap = devm_regmap_init_i2c(client, &afe4404_regmap_config);
+ if (IS_ERR(afe440x->regmap)) {
+ dev_err(afe440x->dev, "Unable to allocate register map\n");
+ return PTR_ERR(afe440x->regmap);
+ }
+ afe440x->regulator = devm_regulator_get(afe440x->dev, "led");
+ if (IS_ERR(afe440x->regulator)) {
+ dev_err(afe440x->dev, "Unable to get regulator\n");
+ return PTR_ERR(afe440x->regulator);
+ }
+ ret = regmap_write(afe440x->regmap, AFE440X_CONTROL0,
+ if (ret) {
+ dev_err(afe440x->dev, "Unable to reset device\n");
+ return ret;
+ }
+ ret = regmap_register_patch(afe440x->regmap, afe4404_reg_sequences,
+ ARRAY_SIZE(afe4404_reg_sequences));
Cool. Never knew that one existed before...
+ if (ret) {
+ dev_err(afe440x->dev, "Unable to set register defaults\n");
+ return ret;
+ }
+ afe440x->channels = afe4404_channels;
+ afe440x->num_channels = ARRAY_SIZE(afe4404_channels);
+ afe440x->name = AFE4404_DRIVER_NAME;
+ afe440x->info = &afe4404_iio_info;
+ return afe440x_iio_setup(afe440x);
+static const struct i2c_device_id afe4404_ids[] = {
+ { "afe4404", 0 },
+ { /* sentinel */ },
+MODULE_DEVICE_TABLE(i2c, afe4404_ids);
+static struct i2c_driver afe4404_i2c_driver = {
+ .driver = {
+ .name = AFE4404_DRIVER_NAME,
+ .of_match_table = of_match_ptr(afe4404_of_match),
+ .pm = &afe440x_pm_ops,
+ },
+ .probe = afe4404_probe,
+ .id_table = afe4404_ids,
+MODULE_AUTHOR("Andrew F. Davis <afd@xxxxxx>");
+MODULE_DESCRIPTION("TI AFE4404 Heart Rate and Pulse Oximeter");
diff --git a/drivers/iio/health/afe440x.h b/drivers/iio/health/afe440x.h
new file mode 100644
index 0000000..2d98a20
--- /dev/null
+++ b/drivers/iio/health/afe440x.h
@@ -0,0 +1,159 @@
+ * AFE440X Heart Rate Monitors and Low-Cost Pulse Oximeters
+ *
+ * Author: Andrew F. Davis <afd@xxxxxx>
+ *
+ * Copyright: (C) 2015 Texas Instruments, Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * General Public License for more details.
+ */
+#ifndef _AFE440X_H
+#define _AFE440X_H
+/* AFE440X registers */
+#define AFE440X_CONTROL0 0x00
+#define AFE440X_LED2STC 0x01
+#define AFE440X_LED2ENDC 0x02
+#define AFE440X_LED1LEDSTC 0x03
+#define AFE440X_LED1LEDENDC 0x04
+#define AFE440X_ALED2STC 0x05
+#define AFE440X_ALED2ENDC 0x06
+#define AFE440X_LED1STC 0x07
+#define AFE440X_LED1ENDC 0x08
+#define AFE440X_LED2LEDSTC 0x09
+#define AFE440X_LED2LEDENDC 0x0a
+#define AFE440X_ALED1STC 0x0b
+#define AFE440X_ALED1ENDC 0x0c
+#define AFE440X_LED2CONVST 0x0d
+#define AFE440X_LED2CONVEND 0x0e
+#define AFE440X_ALED2CONVST 0x0f
+#define AFE440X_ALED2CONVEND 0x10
+#define AFE440X_LED1CONVST 0x11
+#define AFE440X_LED1CONVEND 0x12
+#define AFE440X_ALED1CONVST 0x13
+#define AFE440X_ALED1CONVEND 0x14
+#define AFE440X_ADCRSTSTCT0 0x15
+#define AFE440X_ADCRSTENDCT0 0x16
+#define AFE440X_ADCRSTSTCT1 0x17
+#define AFE440X_ADCRSTENDCT1 0x18
+#define AFE440X_ADCRSTSTCT2 0x19
+#define AFE440X_ADCRSTENDCT2 0x1a
+#define AFE440X_ADCRSTSTCT3 0x1b
+#define AFE440X_ADCRSTENDCT3 0x1c
+#define AFE440X_PRPCOUNT 0x1d
+#define AFE440X_CONTROL1 0x1e
+#define AFE440X_TIAGAIN 0x20
+#define AFE440X_TIA_AMB_GAIN 0x21
+#define AFE440X_LEDCNTRL 0x22
+#define AFE440X_CONTROL2 0x23
+#define AFE440X_ALARM 0x29
+#define AFE440X_LED2VAL 0x2a
+#define AFE440X_ALED2VAL 0x2b
+#define AFE440X_LED1VAL 0x2c
+#define AFE440X_ALED1VAL 0x2d
+#define AFE440X_LED2_ALED2VAL 0x2e
+#define AFE440X_LED1_ALED1VAL 0x2f
+#define AFE440X_CONTROL3 0x31
+#define AFE440X_PDNCYCLESTC 0x32
+#define AFE440X_PDNCYCLEENDC 0x33
+/* CONTROL0 register fields */
+/* CONTROL1 register fields */
+/* TIAGAIN register fields */
+/* CONTROL2 register fields */
+#define AFE440X_CONTROL2_PDN_AFE BIT(0)
+#define AFE440X_CONTROL2_PDN_RX BIT(1)
+#define AFE440X_CONTROL2_DYNAMIC2 BIT(14)
+#define AFE440X_CONTROL2_DYNAMIC1 BIT(20)
+/* CONTROL3 register fields */
+/* CONTROL0 values */
+#define AFE440X_CONTROL0_WRITE 0x0
+#define AFE440X_CONTROL0_READ 0x1
+#define AFE440X_READ_CHAN(_index, _name, _address) \
+ { \
+ .type = IIO_INTENSITY, \
+ .channel = _index, \
+ .address = _address, \
+ .scan_index = _index, \
+ .scan_type = { \
+ .sign = 's', \
+ .realbits = 24, \
+ .storagebits = 32, \
+ .endianness = IIO_CPU, \
+ }, \
+ .extend_name = _name, \
+ .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
+ }
+struct afe440x_reg {
+ struct device_attribute dev_attr;
+ u8 reg;
+ unsigned long shift;
+ unsigned long mask;
+#define to_afe440x_reg(_dev_attr) \
+ container_of(_dev_attr, struct afe440x_reg, dev_attr)
+#define AFE440X_ATTR(_name, _reg, _field) \
+ struct afe440x_reg afe440x_reg_##_name = { \
+ .dev_attr = __ATTR(_name, (S_IRUGO | S_IWUSR), \
+ afe440x_show_register, \
+ afe440x_store_register), \
+ .reg = _reg, \
+ .shift = _field ## _SHIFT, \
+ .mask = _field ## _MASK, \
+ }
+ * struct afe440x_data
+ * @dev - Device structure
+ * @name - Device name
+ * @spi - SPI device pointer the driver is attached to
+ * @iolock - Read/Write mutex
+ * @regmap - Register map of the device
+ * @regulator - Pointer to the regulator for the IC
+ * @channels - IIO channels
+ * @num_channels - Number of IIO channels
+ * @info - IIO info for device
+ * @trig - IIO trigger for this device
+ * @irq - ADC_RDY line interrupt number
+struct afe440x_data {
+ struct device *dev;
This is used in remarkably few places and those are all effectively
in the device probe. Perhaps just passing it directly would make sense.

+ const char *name;
Why have another instance of name given it's held in the iio_dev anyway?

+ struct spi_device *spi;
Not used anywhere that I can find.

This structure is common to the AFE4404 and AFE4403, storing the spi_device
is only needed for the AFE4403 (I'm hoping to use regmap for both and remove
this but the AFE4403's SPI interface seems non-standard and so incompatible
with regmap, but I'm still testing this).

+ struct mutex iolock;
Another one not used anywhere (left-overs from pre regmap?)

Same as above, used for the SPI devices.

+ struct regmap *regmap;
+ struct regulator *regulator;
+ struct iio_chan_spec const *channels;
+ int num_channels;
Having the above in here as well makes limited sense given the versions
in iio_dev are identical.

I'm guessing some of this was due to how the modular stuff you refer
to in the cover letter was done. However, I'm suspecting that was
done less than cleanly to end up with this mixture of constant and non
constant elements in here. There should have been a chip_info structure
consisting of entirely constant elements (such as channels etc) rather than
this combined structure.

+ const struct iio_info *info;
Again, can't see any reason to ever have this directly in here.

All of the above are there so I can pass just an afe440x_data to the driver
core and have it do the initilizing, which is identical for these devices
outside of those structures. I could probably use a chip_info like you said
though for this.

+ struct iio_trigger *trig;
+ int irq;
+#endif /* _AFE440X_H */

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