Re: [PATCH v5 12/17] iio: buffer: introduce support for attaching more IIO buffers

From: Alexandru Ardelean
Date: Sun Feb 14 2021 - 09:38:23 EST

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On Sun, Feb 14, 2021 at 4:02 PM Alexandru Ardelean
<ardeleanalex@xxxxxxxxx> wrote:
>
> On Sun, Feb 14, 2021 at 3:21 PM Jonathan Cameron <jic23@xxxxxxxxxx> wrote:
> >
> > On Thu, 11 Feb 2021 14:24:47 +0200
> > Alexandru Ardelean <alexandru.ardelean@xxxxxxxxxx> 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.
> > >
> > > The iio_device_attach_buffer() is also changed to return an error code,
> > > which for now is -ENOMEM if the array could not be realloc-ed for more
> > > buffers.
> >
> > This is called from a bunch of places, so we need to add error handling
> > for those which isn't currently present.
> >
> > Now arguably it is unlikely to fail, so I'm not that bothered about seeing
> > them all in place as part of this series, but I would like the handling
> > to have been posted at least.
>
> I know what you're referring to.
> I have a slightly better approach before updating this.
> I was going to send it a little later.
> I wanted to send it earlier, but I wanted to avoid overlapping myself
> with too many patches.
> Let me send something now [since it is ready].

So, coming back here.
See series [1]:
https://lore.kernel.org/linux-iio/20210214143313.67202-1-alexandru.ardelean@xxxxxxxxxx/T/#t

I could probably re-spin this series on top of series [1].
That would make things cleaner in terms of handling
iio_device_attach_buffer() in just 2 places I think.

>
> >
> > Otherwise, a few passing comments in here, but nothing to actually change.
> >
> >
> > Jonathan
> >
> > >
> > > Signed-off-by: Alexandru Ardelean <alexandru.ardelean@xxxxxxxxxx>
> > > ---
> > > drivers/iio/iio_core.h | 2 +
> > > drivers/iio/industrialio-buffer.c | 96 +++++++++++++++++++++++++------
> > > drivers/iio/industrialio-core.c | 6 +-
> > > include/linux/iio/buffer.h | 4 +-
> > > include/linux/iio/buffer_impl.h | 3 +
> > > include/linux/iio/iio-opaque.h | 4 ++
> > > 6 files changed, 93 insertions(+), 22 deletions(-)
> > >
> > > diff --git a/drivers/iio/iio_core.h b/drivers/iio/iio_core.h
> > > index 87868fff7d37..4690c3240a5d 100644
> > > --- a/drivers/iio/iio_core.h
> > > +++ b/drivers/iio/iio_core.h
> > > @@ -77,6 +77,7 @@ void iio_buffer_free_sysfs_and_mask(struct iio_dev *indio_dev);
> > >
> > > void iio_disable_all_buffers(struct iio_dev *indio_dev);
> > > void iio_buffer_wakeup_poll(struct iio_dev *indio_dev);
> > > +void iio_buffers_put(struct iio_dev *indio_dev);
> > >
> > > #else
> > >
> > > @@ -92,6 +93,7 @@ static inline void iio_buffer_free_sysfs_and_mask(struct iio_dev *indio_dev) {}
> > >
> > > static inline void iio_disable_all_buffers(struct iio_dev *indio_dev) {}
> > > static inline void iio_buffer_wakeup_poll(struct iio_dev *indio_dev) {}
> > > +static inline void iio_buffers_put(struct iio_dev *indio_dev) {}
> > >
> > > #endif
> > >
> > > diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c
> > > index 209b3a32bdbb..1e8e4c2ff00e 100644
> > > --- a/drivers/iio/industrialio-buffer.c
> > > +++ b/drivers/iio/industrialio-buffer.c
> > > @@ -193,12 +193,14 @@ __poll_t iio_buffer_poll(struct file *filp,
> > > */
> > > void iio_buffer_wakeup_poll(struct iio_dev *indio_dev)
> > > {
> > > - struct iio_buffer *buffer = indio_dev->buffer;
> > > -
> > > - if (!buffer)
> > > - return;
> > > + struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
> > > + struct iio_buffer *buffer;
> > > + unsigned int i;
> > >
> > > - wake_up(&buffer->pollq);
> > > + for (i = 0; i < iio_dev_opaque->attached_buffers_cnt; i++) {
> > > + buffer = iio_dev_opaque->attached_buffers[i];
> > > + wake_up(&buffer->pollq);
> > > + }
> > > }
> > >
> > > void iio_buffer_init(struct iio_buffer *buffer)
> > > @@ -212,6 +214,18 @@ void iio_buffer_init(struct iio_buffer *buffer)
> > > }
> > > EXPORT_SYMBOL(iio_buffer_init);
> > >
> > > +void iio_buffers_put(struct iio_dev *indio_dev)
> > > +{
> > > + struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
> > > + struct iio_buffer *buffer;
> > > + unsigned int i;
> > > +
> > > + for (i = 0; i < iio_dev_opaque->attached_buffers_cnt; i++) {
> > > + buffer = iio_dev_opaque->attached_buffers[i];
> > > + iio_buffer_put(buffer);
> > > + }
> > > +}
> > > +
> > > static ssize_t iio_show_scan_index(struct device *dev,
> > > struct device_attribute *attr,
> > > char *buf)
> > > @@ -1453,9 +1467,11 @@ 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_buffer *buffer = indio_dev->buffer;
> > > + struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
> > > const struct iio_chan_spec *channels;
> > > - int i;
> > > + struct iio_buffer *buffer;
> > > + int unwind_idx;
> > > + int ret, i;
> > >
> > > channels = indio_dev->channels;
> > > if (channels) {
> > > @@ -1466,22 +1482,46 @@ int iio_buffer_alloc_sysfs_and_mask(struct iio_dev *indio_dev)
> > > indio_dev->masklength = ml;
> > > }
> > >
> > > - if (!buffer)
> > > + if (!iio_dev_opaque->attached_buffers_cnt)
> > > return 0;
> > >
> > > - return __iio_buffer_alloc_sysfs_and_mask(buffer, indio_dev, 0);
> > > + 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) {
> > > + unwind_idx = i;
> > > + goto error_unwind_sysfs_and_mask;
> > > + }
> > > + }
> > > +
> > > + return 0;
> > > +
> > > +error_unwind_sysfs_and_mask:
> > > + for (; unwind_idx >= 0; unwind_idx--) {
> > > + buffer = iio_dev_opaque->attached_buffers[unwind_idx];
> > > + __iio_buffer_free_sysfs_and_mask(buffer);
> > > + }
> > > + kfree(iio_dev_opaque->attached_buffers);
> > > + return ret;
> > > }
> > >
> > > void iio_buffer_free_sysfs_and_mask(struct iio_dev *indio_dev)
> > > {
> >
> > Perhaps we should do a follow up adjusting names to slightly better
> > reflect they are not handling multiple buffers.
> >
> > > - struct iio_buffer *buffer = indio_dev->buffer;
> > > + struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
> > > + struct iio_buffer *buffer;
> > > + int i;
> > >
> > > - if (!buffer)
> > > + if (!iio_dev_opaque->attached_buffers_cnt)
> > > return;
> > >
> > > iio_buffer_unregister_legacy_sysfs_groups(indio_dev);
> > >
> > > - __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);
> >
> > Hmm. This does feel like it's in slightly the wrong place, but
> > I'm not sure where it actually should be.
> >
> > Given this is the last element in the call sequence I guess it doesn't
> > makes sense to bring in another function just to tidy up this connection.
> >
> > > }
> > >
> > > /**
> > > @@ -1599,13 +1639,35 @@ EXPORT_SYMBOL_GPL(iio_buffer_put);
> > > * @indio_dev: The device the buffer should be attached to
> > > * @buffer: The buffer to attach to the device
> > > *
> > > + * Return 0 if successful, negative if error.
> > > + *
> > > * 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)
> > > +int 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)
> > > + return -ENOMEM;
> > > + iio_dev_opaque->attached_buffers = new;
> > > +
> > > + buffer = iio_buffer_get(buffer);
> > > +
> > > + /* first buffer is legacy; attach it to the IIO device directly */
> > > + if (!indio_dev->buffer)
> > > + indio_dev->buffer = buffer;
> > > +
> > > + iio_dev_opaque->attached_buffers[cnt - 1] = buffer;
> > > + iio_dev_opaque->attached_buffers_cnt = cnt;
> > > +
> > > + return 0;
> > > }
> > > EXPORT_SYMBOL_GPL(iio_device_attach_buffer);
> > > diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
> > > index 1be94df3e591..26b05dddfa71 100644
> > > --- a/drivers/iio/industrialio-core.c
> > > +++ b/drivers/iio/industrialio-core.c
> > > @@ -1583,7 +1583,7 @@ static void iio_dev_release(struct device *device)
> > > iio_device_unregister_eventset(indio_dev);
> > > iio_device_unregister_sysfs(indio_dev);
> > >
> > > - iio_buffer_put(indio_dev->buffer);
> > > + iio_buffers_put(indio_dev);
> > >
> > > ida_simple_remove(&iio_ida, indio_dev->id);
> > > kfree(iio_dev_opaque);
> > > @@ -1884,12 +1884,12 @@ int __iio_device_register(struct iio_dev *indio_dev, struct module *this_mod)
> > > indio_dev->setup_ops == NULL)
> > > indio_dev->setup_ops = &noop_ring_setup_ops;
> > >
> > > - if (indio_dev->buffer)
> > > + if (iio_dev_opaque->attached_buffers_cnt)
> > > cdev_init(&indio_dev->chrdev, &iio_buffer_fileops);
> > > else if (iio_dev_opaque->event_interface)
> > > cdev_init(&indio_dev->chrdev, &iio_event_fileops);
> > >
> > > - if (indio_dev->buffer || iio_dev_opaque->event_interface) {
> > > + if (iio_dev_opaque->attached_buffers_cnt || iio_dev_opaque->event_interface) {
> > > indio_dev->dev.devt = MKDEV(MAJOR(iio_devt), indio_dev->id);
> > > indio_dev->chrdev.owner = this_mod;
> > > }
> > > diff --git a/include/linux/iio/buffer.h b/include/linux/iio/buffer.h
> > > index 8febc23f5f26..b6928ac5c63d 100644
> > > --- a/include/linux/iio/buffer.h
> > > +++ b/include/linux/iio/buffer.h
> > > @@ -41,7 +41,7 @@ static inline int iio_push_to_buffers_with_timestamp(struct iio_dev *indio_dev,
> > > bool iio_validate_scan_mask_onehot(struct iio_dev *indio_dev,
> > > const unsigned long *mask);
> > >
> > > -void iio_device_attach_buffer(struct iio_dev *indio_dev,
> > > - struct iio_buffer *buffer);
> > > +int iio_device_attach_buffer(struct iio_dev *indio_dev,
> > > + struct iio_buffer *buffer);
> > >
> > > #endif /* _IIO_BUFFER_GENERIC_H_ */
> > > diff --git a/include/linux/iio/buffer_impl.h b/include/linux/iio/buffer_impl.h
> > > index 41044320e581..768b90c64412 100644
> > > --- a/include/linux/iio/buffer_impl.h
> > > +++ b/include/linux/iio/buffer_impl.h
> > > @@ -112,6 +112,9 @@ 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 3e4c3cd248fd..c909835b6247 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
> > > @@ -24,6 +26,8 @@
> > > 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;
> >

Next message: Dejin Zheng: "[PATCH] i2c: thunderx: Fix an issue about missing call to 'pci_free_irq_vectors()'"
Previous message: Jonathan Cameron: "Re: [PATCH v5 13/17] iio: buffer: add ioctl() to support opening extra buffers for IIO device"
In reply to: Alexandru Ardelean: "Re: [PATCH v5 12/17] iio: buffer: introduce support for attaching more IIO buffers"
Next in thread: Alexandru Ardelean: "[PATCH v5 11/17] iio: buffer: move __iio_buffer_free_sysfs_and_mask() before alloc"
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