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Date: Sat, 21 Nov 2020 18:44:45 +0000
From: Jonathan Cameron <jic23@...nel.org>
To: Alexandru Ardelean <alexandru.ardelean@...log.com>
Cc: <linux-iio@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
<lars@...afoo.de>
Subject: Re: [RFC PATCH 11/12] iio: buffer: introduce support for attaching
more IIO buffers
On Tue, 17 Nov 2020 18:23:39 +0200
Alexandru Ardelean <alexandru.ardelean@...log.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@...log.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.
> +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.
> + 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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