Re: [RFC][PATCH v1] ACPI / scan: Create platform device for BOSC0200 ACPI nodes

From: Hans de Goede
Date: Tue Oct 30 2018 - 14:52:39 EST


On 30-10-18 16:27, Hans de Goede wrote:

On 30-10-18 15:47, Andy Shevchenko wrote:
On some laptops the ACPI device with BOSC0200 _HID is representing
two accelerometers under one node.

We add an ID to the I2C multi instantiate list to enumerate
all I2C slaves correctly.

I believe that overall the approach here is correct, but I've
several (at least 4 different models) devices which use the
BOSC0200 _HID but with only 1 accelerometer / 1 I2cSerialBus
resource in the _CRS table.

So I believe that you need to add a new optional bool to
struct i2c_inst_data and ignore i2c_acpi_new_device()
returning NULL when this is set (and set it for the second

i2c_unregister_device can handle NULL, so some entries
of the multi->clients[i] array ending up as NULL is not
a problem.

Hmm, I have just realized that there is another issue
which is a real problem, we have stuff like this:

[hans@shalem linux]$ ack BOSC0200 /lib/udev/hwdb.d/60-sensor.hwdb
# match the entire dmi-alias, assuming that the use of a BOSC0200 +

And using i2c-multi-instantiate will change the modalias from
acpi:BOSC0200 to i2c:bmc150_accel breaking this.

One way to fix this would be making sure we only use an
i2c:bmc150_accel modalias for the second device. This will
also allow differentiating between the 2 in hwdb quirks for
devices with 2 accelerometers. But the way we currently
generate modalias-es does not allow doing this in an
easy way. Making this possible will require some changes to
show_modalias() and i2c_device_uevent() in

Ok, new idea how about we modify the code in acpi_device_enumeration_by_parent
to instead of looking at a HID list, to simply count if there is more then
1 I2cSerialBus resource and if that is the case enumerate the device as
a platform device for i2c-multi-instantiate.c to handle. This means that
we will only change the way how the BOSC0200 is enumerated on the
Yoga 11e and not elsewhere.

This is somewhat likely to trigger a regression somewhere, but we should
be able to fix those regressions by adding the necessary info to
i2c-multi-instantiate.c. Then it could still be a problem because of
the modalias changing for an i2c device from some other DSDT which we
are not aware of yet, but that only is a problem if the modalias is
used in hwdb. The actual driver for the hardware should bind to the
new modalias too and if not we can fix that.

I believe the amount of devices which turn out to have more then 1
I2cSerialBus resource will be small and the set of devices which are already
working somehow (because the 1st resource is the one we care about) and also
have a hwdb entry will likely be very small and we can help users who
hit this combo by providing hwdb patches.


Hmm, a quick random spot check of a few of the too many DSTDs I have
turns out that at least the INT34D3 (Intel Whiskey Cove PMIC) will
be bitten by this. This is trivial to fix though.

And another one is the "CPLM3218" ambient light sensor, which does
not have an in tree driver, but there is an out of tree one which
is on my list to upstream...

This will also cause us to stop generating i2c-clients for some of
the camera sensors on BYT/CHT since some list multiple (some up to 10 ???)
addresses I guess this is for some sorta auto-probe function in
the windows drivers.

TL;DR: the idea of just checking for multiple I2cSerialBus resources
in a single acpi_fwnode is interesting, but might cause more problems
then I would hope.