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iio: Add output buffer support

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Currently IIO only supports buffer mode for capture devices like ADCs. Add
support for buffered mode for output devices like DACs.

The output buffer implementation is analogous to the input buffer
implementation. Instead of using read() to get data from the buffer write()
is used to copy data into the buffer.

poll() with POLLOUT will wakeup if there is space available.

Drivers can remove data from a buffer using iio_pop_from_buffer(), the
function can e.g. called from a trigger handler to write the data to
hardware.

A buffer can only be either a output buffer or an input, but not both. So,
for a device that has an ADC and DAC path, this will mean 2 IIO buffers
(one for each direction).

The direction of the buffer is decided by the new direction field of the
iio_buffer struct and should be set after allocating and before registering
it.

Co-developed-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Co-developed-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Signed-off-by: Mihail Chindris <mihail.chindris@analog.com>
Link: https://lore.kernel.org/r/20211007080035.2531-2-mihail.chindris@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
This commit is contained in:
Mihail Chindris
2021-10-07 08:00:30 +00:00
committed by Jonathan Cameron
parent d6fa140630
commit 9eeee3b0bf
5 changed files with 148 additions and 2 deletions
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7
include/linux/iio/buffer.h
View File

@@ -11,8 +11,15 @@
struct iio_buffer;
enum iio_buffer_direction {
IIO_BUFFER_DIRECTION_IN,
IIO_BUFFER_DIRECTION_OUT,
};
int iio_push_to_buffers(struct iio_dev *indio_dev, const void *data);
int iio_pop_from_buffer(struct iio_buffer *buffer, void *data);
/**
* iio_push_to_buffers_with_timestamp() - push data and timestamp to buffers
* @indio_dev: iio_dev structure for device.