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SubjectRe: [RFC PATCH 11/12] iio: buffer: introduce support for attaching more IIO buffers
On Sat, Nov 21, 2020 at 8:46 PM Jonathan Cameron <jic23@kernel.org> wrote:
>
> On Tue, 17 Nov 2020 18:23:39 +0200
> Alexandru Ardelean <alexandru.ardelean@analog.com> wrote:
>
> > With this change, calling iio_device_attach_buffer() will actually attach
> > more buffers.
> > Right now this doesn't do any validation of whether a buffer is attached
> > twice; maybe that can be added later (if needed). Attaching a buffer more
> > than once should yield noticeably bad results.
> >
> > The first buffer is the legacy buffer, so a reference is kept to it.
> >
> > At this point, accessing the data for the extra buffers (that are added
> > after the first one) isn't possible yet.
> >
> > Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
> A couple of minor things in here..
>
> Jonathan
>
> > ---
> > drivers/iio/industrialio-buffer.c | 58 +++++++++++++++++++++++++------
> > include/linux/iio/buffer_impl.h | 3 ++
> > include/linux/iio/iio-opaque.h | 4 +++
> > 3 files changed, 54 insertions(+), 11 deletions(-)
> >
> > diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c
> > index c83cec89eddf..daa68822cea7 100644
> > --- a/drivers/iio/industrialio-buffer.c
> > +++ b/drivers/iio/industrialio-buffer.c
> > @@ -1513,6 +1513,7 @@ static void __iio_buffer_free_sysfs_and_mask(struct iio_buffer *buffer);
> >
> > int iio_buffer_alloc_sysfs_and_mask(struct iio_dev *indio_dev)
> > {
> > + struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
> > struct iio_buffer *buffer = indio_dev->buffer;
> > const struct iio_chan_spec *channels;
> > int i, ret;
> > @@ -1529,15 +1530,18 @@ int iio_buffer_alloc_sysfs_and_mask(struct iio_dev *indio_dev)
> > if (!buffer)
> > return 0;
> >
> > - ret = __iio_buffer_alloc_sysfs_and_mask(buffer, indio_dev, 0);
> > - if (ret)
> > - return ret;
> > + for (i = 0; i < iio_dev_opaque->attached_buffers_cnt; i++) {
> > + buffer = iio_dev_opaque->attached_buffers[i];
> > + ret = __iio_buffer_alloc_sysfs_and_mask(buffer, indio_dev, i);
> > + if (ret)
> > + goto error_unwind_sysfs_and_mask;
> > + }
> >
> > ret = sysfs_create_link(&indio_dev->dev.kobj,
> > &indio_dev->buffer->buffer_dir,
> > "buffer");
> > if (ret)
> > - goto error_free_sysfs_and_mask;
> > + goto error_unwind_sysfs_and_mask;
> >
> > ret = sysfs_create_link(&indio_dev->dev.kobj,
> > &indio_dev->buffer->scan_el_dir,
> > @@ -1549,8 +1553,14 @@ int iio_buffer_alloc_sysfs_and_mask(struct iio_dev *indio_dev)
> >
> > error_remove_buffer_dir_link:
> > sysfs_remove_link(&indio_dev->dev.kobj, "buffer");
> > -error_free_sysfs_and_mask:
> > - __iio_buffer_free_sysfs_and_mask(buffer);
> > + i = iio_dev_opaque->attached_buffers_cnt - 1;
>
> Perhaps just use a counter variable that is only for this then you won't need
> to set it again in this error path.

Ack.

>
> > +error_unwind_sysfs_and_mask:
> > + for (; i >= 0; i--) {
> > + buffer = iio_dev_opaque->attached_buffers[i];
> > + __iio_buffer_free_sysfs_and_mask(buffer);
> > + }
> > + kfree(iio_dev_opaque->attached_buffers);
> > + iio_dev_opaque->attached_buffers = NULL;
> > return ret;
> > }
> >
> > @@ -1568,7 +1578,9 @@ static void __iio_buffer_free_sysfs_and_mask(struct iio_buffer *buffer)
> >
> > void iio_buffer_free_sysfs_and_mask(struct iio_dev *indio_dev)
> > {
> > + struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
> > struct iio_buffer *buffer = indio_dev->buffer;
> > + int i;
> >
> > if (!buffer)
> > return;
> > @@ -1576,7 +1588,13 @@ void iio_buffer_free_sysfs_and_mask(struct iio_dev *indio_dev)
> > sysfs_remove_link(&indio_dev->dev.kobj, "scan_elements");
> > sysfs_remove_link(&indio_dev->dev.kobj, "buffer");
> >
> > - __iio_buffer_free_sysfs_and_mask(buffer);
> > + for (i = iio_dev_opaque->attached_buffers_cnt - 1; i >= 0; i--) {
> > + buffer = iio_dev_opaque->attached_buffers[i];
> > + __iio_buffer_free_sysfs_and_mask(buffer);
> > + }
> > +
> > + kfree(iio_dev_opaque->attached_buffers);
> > + iio_dev_opaque->attached_buffers = NULL;
> > }
> >
> > /**
> > @@ -1709,14 +1727,32 @@ EXPORT_SYMBOL_GPL(iio_buffer_get_iio_dev);
> > * @buffer: The buffer to attach to the device
> > *
> > * This function attaches a buffer to a IIO device. The buffer stays attached to
> > - * the device until the device is freed. The function should only be called at
> > - * most once per device.
> > + * the device until the device is freed. For legacy reasons, the first attached
> > + * buffer will also be assigned to 'indio_dev->buffer'.
> > */
> > void iio_device_attach_buffer(struct iio_dev *indio_dev,
> > struct iio_buffer *buffer)
> > {
> > - indio_dev->buffer = iio_buffer_get(buffer);
> > + struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
> > + struct iio_buffer **new, **old = iio_dev_opaque->attached_buffers;
> > + unsigned int cnt = iio_dev_opaque->attached_buffers_cnt;
> > +
> > + cnt++;
> > +
> > + new = krealloc(old, sizeof(*new) * cnt, GFP_KERNEL);
> > + if (!new) {
> > + kfree(old);
>
> Need a comment on why freeing old makes sense.

Hmm, maybe here I'd need to change this a bit.
I'm seeing a few potential issues.

>
> > + return;
> > + }
> > + iio_dev_opaque->attached_buffers = new;
> > +
> > + /* first buffer is legacy; attach it to the IIO device directly */
> > + if (!indio_dev->buffer)
> > + indio_dev->buffer = iio_buffer_get(buffer);
> > +
> > + buffer->indio_dev = indio_dev;
> >
> > - indio_dev->buffer->indio_dev = indio_dev;
> > + iio_dev_opaque->attached_buffers[cnt - 1] = buffer;
> > + iio_dev_opaque->attached_buffers_cnt = cnt;
> > }
> > EXPORT_SYMBOL_GPL(iio_device_attach_buffer);
> > diff --git a/include/linux/iio/buffer_impl.h b/include/linux/iio/buffer_impl.h
> > index 77e169e51434..e25d26a7f601 100644
> > --- a/include/linux/iio/buffer_impl.h
> > +++ b/include/linux/iio/buffer_impl.h
> > @@ -124,6 +124,9 @@ struct iio_buffer {
> > /* @demux_bounce: Buffer for doing gather from incoming scan. */
> > void *demux_bounce;
> >
> > + /* @attached_entry: Entry in the devices list of buffers attached by the driver. */
> > + struct list_head attached_entry;
> > +
> > /* @buffer_list: Entry in the devices list of current buffers. */
> > struct list_head buffer_list;
> >
> > diff --git a/include/linux/iio/iio-opaque.h b/include/linux/iio/iio-opaque.h
> > index 07c5a8e52ca8..1db0ea09520e 100644
> > --- a/include/linux/iio/iio-opaque.h
> > +++ b/include/linux/iio/iio-opaque.h
> > @@ -7,6 +7,8 @@
> > * struct iio_dev_opaque - industrial I/O device opaque information
> > * @indio_dev: public industrial I/O device information
> > * @event_interface: event chrdevs associated with interrupt lines
> > + * @attached_buffers: array of buffers statically attached by the driver
> > + * @attached_buffers_cnt: number of buffers in the array of statically attached buffers
> > * @buffer_list: list of all buffers currently attached
> > * @channel_attr_list: keep track of automatically created channel
> > * attributes
> > @@ -20,6 +22,8 @@
> > struct iio_dev_opaque {
> > struct iio_dev indio_dev;
> > struct iio_event_interface *event_interface;
> > + struct iio_buffer **attached_buffers;
> > + unsigned int attached_buffers_cnt;
> > struct list_head buffer_list;
> > struct list_head channel_attr_list;
> > struct attribute_group chan_attr_group;
>

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