iio: buffer: introduce support for attaching more IIO buffers

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.
To adapt to this new change iio_device_attach_buffer() is called last in
all place where it's called. The realloc failure is a bit difficult to
handle during un-managed calls when unwinding, so it's better to have this
as the last error in the setup_buffer calls.

At this point, no driver should call iio_device_attach_buffer() directly,
it should call one of the {devm_}iio_triggered_buffer_setup() or
devm_iio_kfifo_buffer_setup() or devm_iio_dmaengine_buffer_setup()
functions. This makes iio_device_attach_buffer() a bit easier to handle.

Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Link: https://lore.kernel.org/r/20210215104043.91251-20-alexandru.ardelean@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

1 files changed, 6 insertions, 4 deletions

diff --git a/drivers/iio/iio_core.h b/drivers/iio/iio_core.h
index 87868fff7d37..7990c759f1f5 100644
--- a/drivers/iio/iio_core.h
+++ b/drivers/iio/iio_core.h
@@ -69,29 +69,31 @@ __poll_t iio_buffer_poll(struct file *filp,
 ssize_t iio_buffer_read_outer(struct file *filp, char __user *buf,
 			      size_t n, loff_t *f_ps);
 
-int iio_buffer_alloc_sysfs_and_mask(struct iio_dev *indio_dev);
-void iio_buffer_free_sysfs_and_mask(struct iio_dev *indio_dev);
+int iio_buffers_alloc_sysfs_and_mask(struct iio_dev *indio_dev);
+void iio_buffers_free_sysfs_and_mask(struct iio_dev *indio_dev);
 
 #define iio_buffer_poll_addr (&iio_buffer_poll)
 #define iio_buffer_read_outer_addr (&iio_buffer_read_outer)
 
 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
 
 #define iio_buffer_poll_addr NULL
 #define iio_buffer_read_outer_addr NULL
 
-static inline int iio_buffer_alloc_sysfs_and_mask(struct iio_dev *indio_dev)
+static inline int iio_buffers_alloc_sysfs_and_mask(struct iio_dev *indio_dev)
 {
 	return 0;
 }
 
-static inline void iio_buffer_free_sysfs_and_mask(struct iio_dev *indio_dev) {}
+static inline void iio_buffers_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