Re: [RFC PATCH 1/4] iio: Move scan mask management to the core

From: Ardelean, Alexandru
Date: Mon Apr 27 2020 - 02:25:38 EST

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On Sun, 2020-04-26 at 10:45 +0100, Jonathan Cameron wrote:
> [External]
>
> On Fri, 24 Apr 2020 08:18:15 +0300
> Alexandru Ardelean <alexandru.ardelean@xxxxxxxxxx> wrote:
>
> > From: Lars-Peter Clausen <lars@xxxxxxxxxx>
> >
> > Let the core handle the buffer scan mask management including allocation
> > and channel selection. Having this handled in a central place rather than
> > open-coding it all over the place will make it easier to change the
> > implementation.
> >
> > Signed-off-by: Lars-Peter Clausen <lars@xxxxxxxxxx>
> > Signed-off-by: Alexandru Ardelean <alexandru.ardelean@xxxxxxxxxx>
>
> Hi Alex,
>
> For some reason I only have patch 1 of this series of 4.
>
> This one looks reasonable to me as abstracts away how it is implemented
> which is good. A few comments and a question inline.
>

Replies inline.

Since the discussion about patches 3 & 4 got a little more complicated [than I'd
like to focus on at this point in time], would it be ok to split patches 1 & 2
into a separate series? [after discussions are resolved]
Even just those 2 patches helps me work on 2 kernel trees [the ADI internal &
the IIO upstream one], as it minimizes the diff.

> Jonathan
>
>
> > ---
> > drivers/iio/buffer/industrialio-buffer-cb.c | 17 ++++------
> > drivers/iio/industrialio-buffer.c | 36 +++++++++++++++------
> > drivers/iio/inkern.c | 15 +++++++++
> > include/linux/iio/consumer.h | 10 ++++++
> > 4 files changed, 58 insertions(+), 20 deletions(-)
> >
> > diff --git a/drivers/iio/buffer/industrialio-buffer-cb.c
> > b/drivers/iio/buffer/industrialio-buffer-cb.c
> > index 47c96f7f4976..b50f1f48cac6 100644
> > --- a/drivers/iio/buffer/industrialio-buffer-cb.c
> > +++ b/drivers/iio/buffer/industrialio-buffer-cb.c
> > @@ -33,8 +33,7 @@ static int iio_buffer_cb_store_to(struct iio_buffer
> > *buffer, const void *data)
> > static void iio_buffer_cb_release(struct iio_buffer *buffer)
> > {
> > struct iio_cb_buffer *cb_buff = buffer_to_cb_buffer(buffer);
> > -
> > - bitmap_free(cb_buff->buffer.scan_mask);
> > + iio_buffer_free_scanmask(buffer);
> > kfree(cb_buff);
> > }
> >
> > @@ -72,27 +71,25 @@ struct iio_cb_buffer *iio_channel_get_all_cb(struct
> > device *dev,
> > }
> >
> > cb_buff->indio_dev = cb_buff->channels[0].indio_dev;
> > - cb_buff->buffer.scan_mask = bitmap_zalloc(cb_buff->indio_dev-
> > >masklength,
> > - GFP_KERNEL);
> > - if (cb_buff->buffer.scan_mask == NULL) {
> > - ret = -ENOMEM;
> > +
> > + ret = iio_buffer_alloc_scanmask(&cb_buff->buffer, cb_buff->indio_dev);
> > + if (ret)
> > goto error_release_channels;
> > - }
> > +
> > chan = &cb_buff->channels[0];
> > while (chan->indio_dev) {
> > if (chan->indio_dev != cb_buff->indio_dev) {
> > ret = -EINVAL;
> > goto error_free_scan_mask;
> > }
> > - set_bit(chan->channel->scan_index,
> > - cb_buff->buffer.scan_mask);
> > + iio_buffer_channel_enable(&cb_buff->buffer, chan);
> > chan++;
> > }
> >
> > return cb_buff;
> >
> > error_free_scan_mask:
> > - bitmap_free(cb_buff->buffer.scan_mask);
> > + iio_buffer_free_scanmask(&cb_buff->buffer);
> > error_release_channels:
> > iio_channel_release_all(cb_buff->channels);
> > error_free_cb_buff:
> > diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-
> > buffer.c
> > index 221157136af6..c06691281287 100644
> > --- a/drivers/iio/industrialio-buffer.c
> > +++ b/drivers/iio/industrialio-buffer.c
> > @@ -206,6 +206,26 @@ void iio_buffer_init(struct iio_buffer *buffer)
> > }
> > EXPORT_SYMBOL(iio_buffer_init);
> >
> > +int iio_buffer_alloc_scanmask(struct iio_buffer *buffer,
> > + struct iio_dev *indio_dev)
> I'm not sure passing the indio_dev in here makes sense as it
> obscures that all we are getting from it is the masklength.
> May be better to pass that explicitly.

Passing indio_dev seems to make more sense if we are also doing the channel_mask
thing in the next patches.
If we do the buffer->indio_dev back-ref, then we can just pass the buffer.
But that may obscure things a bit more about the 'masklength'; though, that may
be one of the intentions I suppose [can't be sure]

>
> > +{
> > + if (!indio_dev->masklength)
> > + return 0;
>
> This is a bit of an oddity of the old code. Any idea why we
> allow things to continue with a masklength of 0? Seems to me
> that it is thoroughly broken if that occurs!

See [1]

>
> > +
> > + buffer->scan_mask = bitmap_zalloc(indio_dev->masklength, GFP_KERNEL);
> > + if (buffer->scan_mask == NULL)
> > + return -ENOMEM;
> > +
> > + return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(iio_buffer_alloc_scanmask);
> > +
> > +void iio_buffer_free_scanmask(struct iio_buffer *buffer)
> > +{
> > + bitmap_free(buffer->scan_mask);
> > +}
> > +EXPORT_SYMBOL_GPL(iio_buffer_free_scanmask);
> > +
> > /**
> > * iio_buffer_set_attrs - Set buffer specific attributes
> > * @buffer: The buffer for which we are setting attributes
> > @@ -1301,14 +1321,10 @@ int iio_buffer_alloc_sysfs_and_mask(struct iio_dev
> > *indio_dev)
> > indio_dev->scan_index_timestamp =
> > channels[i].scan_index;
> > }
> > - if (indio_dev->masklength && buffer->scan_mask == NULL) {

[1] I suspect when this patch was written, it had this part in mind [with the
retun 0]
So, it preserves behavior a bit.
The 'buffer->scan_mask == NULL' check is a bit odd; I wonder if the initial
intent was to also allow to pass a 'scan_mask' from somewhere else.

So, updating '!indio_dev->masklength' to return -EINVAL in
iio_buffer_alloc_scanmask() sounds like a good idea, but I'll need to add a note
in the commit description.

> > - buffer->scan_mask = bitmap_zalloc(indio_dev->masklength,
> > - GFP_KERNEL);
> > - if (buffer->scan_mask == NULL) {
> > - ret = -ENOMEM;
> > - goto error_cleanup_dynamic;
> > - }
> > - }
> > +
> > + ret = iio_buffer_alloc_scanmask(buffer, indio_dev);
> > + if (ret)
> > + goto error_cleanup_dynamic;
> > }
> >
> > buffer->scan_el_group.name = iio_scan_elements_group_name;
> > @@ -1329,7 +1345,7 @@ int iio_buffer_alloc_sysfs_and_mask(struct iio_dev
> > *indio_dev)
> > return 0;
> >
> > error_free_scan_mask:
> > - bitmap_free(buffer->scan_mask);
> > + iio_buffer_free_scanmask(buffer);
> > error_cleanup_dynamic:
> > iio_free_chan_devattr_list(&buffer->scan_el_dev_attr_list);
> > kfree(indio_dev->buffer->buffer_group.attrs);
> > @@ -1342,7 +1358,7 @@ void iio_buffer_free_sysfs_and_mask(struct iio_dev
> > *indio_dev)
> > if (!indio_dev->buffer)
> > return;
> >
> > - bitmap_free(indio_dev->buffer->scan_mask);
> > + iio_buffer_free_scanmask(indio_dev->buffer);
> > kfree(indio_dev->buffer->buffer_group.attrs);
> > kfree(indio_dev->buffer->scan_el_group.attrs);
> > iio_free_chan_devattr_list(&indio_dev->buffer->scan_el_dev_attr_list);
> > diff --git a/drivers/iio/inkern.c b/drivers/iio/inkern.c
> > index ede99e0d5371..f35cb9985edc 100644
> > --- a/drivers/iio/inkern.c
> > +++ b/drivers/iio/inkern.c
> > @@ -11,6 +11,7 @@
> >
> > #include <linux/iio/iio.h>
> > #include "iio_core.h"
> > +#include <linux/iio/buffer_impl.h>
> > #include <linux/iio/machine.h>
> > #include <linux/iio/driver.h>
> > #include <linux/iio/consumer.h>
> > @@ -857,6 +858,20 @@ int iio_write_channel_raw(struct iio_channel *chan, int
> > val)
> > }
> > EXPORT_SYMBOL_GPL(iio_write_channel_raw);
> >
> > +void iio_buffer_channel_enable(struct iio_buffer *buffer,
> > + const struct iio_channel *chan)
> > +{
> > + set_bit(chan->channel->scan_index, buffer->scan_mask);
> > +}
> > +EXPORT_SYMBOL_GPL(iio_buffer_channel_enable);
> > +
> > +void iio_buffer_channel_disable(struct iio_buffer *buffer,
> > + const struct iio_channel *chan)
> > +{
> > + clear_bit(chan->channel->scan_index, buffer->scan_mask);
> > +}
> > +EXPORT_SYMBOL_GPL(iio_buffer_channel_disable);
> > +
> > unsigned int iio_get_channel_ext_info_count(struct iio_channel *chan)
> > {
> > const struct iio_chan_spec_ext_info *ext_info;
> > diff --git a/include/linux/iio/consumer.h b/include/linux/iio/consumer.h
> > index c4118dcb8e05..dbc87c26250a 100644
> > --- a/include/linux/iio/consumer.h
> > +++ b/include/linux/iio/consumer.h
> > @@ -12,6 +12,7 @@
> >
> > struct iio_dev;
> > struct iio_chan_spec;
> > +struct iio_buffer;
> > struct device;
> >
> > /**
> > @@ -342,6 +343,15 @@ int iio_read_channel_scale(struct iio_channel *chan,
> > int *val,
> > int iio_convert_raw_to_processed(struct iio_channel *chan, int raw,
> > int *processed, unsigned int scale);
> >
> > +void iio_buffer_channel_enable(struct iio_buffer *buffer,
> > + const struct iio_channel *chan);
> > +void iio_buffer_channel_disable(struct iio_buffer *buffer,
> > + const struct iio_channel *chan);
> > +
> > +int iio_buffer_alloc_scanmask(struct iio_buffer *buffer,
> > + struct iio_dev *indio_dev);
> > +void iio_buffer_free_scanmask(struct iio_buffer *buffer);
> > +
> > /**
> > * iio_get_channel_ext_info_count() - get number of ext_info attributes
> > * connected to the channel.

Next message: Roy Im: "[RESEND PATCH V11 1/3] MAINTAINERS: da7280 updates to the Dialog Semiconductor search terms"
Previous message: Amit Daniel Kachhap: "[PATCH v2 2/2] Documentation/vmcoreinfo: Add documentation for 'KERNELPACMASK'"
In reply to: Jonathan Cameron: "Re: [RFC PATCH 1/4] iio: Move scan mask management to the core"
Next in thread: Sa, Nuno: "RE: [RFC PATCH 0/4] iio: scan_mask rework to track enabled channels on per-channel basis"
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