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

From: Jonathan Cameron
Date: Sat May 02 2020 - 14:12:50 EST

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On Mon, 27 Apr 2020 06:25:19 +0000
"Ardelean, Alexandru" <alexandru.Ardelean@xxxxxxxxxx> wrote:

> 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.
>

That would be fine.

>
> > 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.

Yup. Sounds good.
>
>
> > > - 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.

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