If dma_get_slave_caps() fails, we need to release the dma channel before
returning an error to avoid leaking the channel.

Fixes: 2d6ca60f3284 ("iio: Add a DMAengine framework based buffer")
Signed-off-by: David Lechner <dlechner@baylibre.com>
Link: https://patch.msgid.link/20240723-iio-fix-dmaengine-free-on-error-v1-1-2c7cbc9b92ff@baylibre.com
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Use the functions provided by the buffer-dma core to implement the
DMABUF userspace API in the buffer-dmaengine IIO buffer implementation.

Since we want to be able to transfer an arbitrary number of bytes and
not necesarily the full DMABUF, the associated scatterlist is converted
to an array of DMA addresses + lengths, which is then passed to
dmaengine_prep_slave_dma_array().

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Co-developed-by: Nuno Sa <nuno.sa@analog.com>
Signed-off-by: Nuno Sa <nuno.sa@analog.com>
Link: https://patch.msgid.link/20240620122726.41232-6-paul@crapouillou.net
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Implement iio_dma_buffer_attach_dmabuf(), iio_dma_buffer_detach_dmabuf()
and iio_dma_buffer_transfer_dmabuf(), which can then be used by the IIO
DMA buffer implementations.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Co-developed-by: Nuno Sa <nuno.sa@analog.com>
Signed-off-by: Nuno Sa <nuno.sa@analog.com>
Link: https://patch.msgid.link/20240620122726.41232-5-paul@crapouillou.net
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

make allmodconfig && make W=1 C=1 reports:
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/iio/adc/ingenic-adc.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/iio/adc/xilinx-ams.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/iio/buffer/kfifo_buf.o

Add the missing invocations of the MODULE_DESCRIPTION() macro.

Signed-off-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Link: https://lore.kernel.org/r/20240607-md-drivers-iic-v1-1-9f9db6246083@quicinc.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Use the iio_dma_buffer_write() and iio_dma_buffer_space_available()
functions provided by the buffer-dma core, to enable write support in
the buffer-dmaengine code.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Reviewed-by: Alexandru Ardelean <ardeleanalex@gmail.com>
Signed-off-by: Nuno Sa <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20240419-iio-backend-axi-dac-v4-5-5ca45b4de294@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Update the devm_iio_dmaengine_buffer_setup() function to support
specifying the buffer direction.

Update the iio_dmaengine_buffer_submit() function to handle input
buffers as well as output buffers.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Reviewed-by: Alexandru Ardelean <ardeleanalex@gmail.com>
Signed-off-by: Nuno Sa <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20240419-iio-backend-axi-dac-v4-4-5ca45b4de294@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Adding write support to the buffer-dma code is easy - the write()
function basically needs to do the exact same thing as the read()
function: dequeue a block, read or write the data, enqueue the block
when entirely processed.

Therefore, the iio_buffer_dma_read() and the new iio_buffer_dma_write()
now both call a function iio_buffer_dma_io(), which will perform this
task.

Note that we preemptively reset block->bytes_used to the buffer's size
in iio_dma_buffer_request_update(), as in the future the
iio_dma_buffer_enqueue() function won't reset it.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Reviewed-by: Alexandru Ardelean <ardeleanalex@gmail.com>
Signed-off-by: Nuno Sa <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20240419-iio-backend-axi-dac-v4-3-5ca45b4de294@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Change its name to iio_dma_buffer_usage(), as this function can be used
both for the .data_available and the .space_available callbacks.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Signed-off-by: Nuno Sa <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20240419-iio-backend-axi-dac-v4-2-5ca45b4de294@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

This brings the DMA buffer API more in line with what we have in the
triggered buffer. There's no need of having both
devm_iio_dmaengine_buffer_setup() and devm_iio_dmaengine_buffer_alloc().
Hence we introduce the new iio_dmaengine_buffer_setup() that together
with devm_iio_dmaengine_buffer_setup() should be all we need.

Note that as part of this change iio_dmaengine_buffer_alloc() is again
static and the axi-adc was updated accordingly.

Signed-off-by: Nuno Sa <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20240419-iio-backend-axi-dac-v4-1-5ca45b4de294@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Export iio_dmaengine_buffer_free() and iio_dmaengine_buffer_alloc().
This is in preparation of introducing IIO backends support. This will
allow us to allocate a buffer and control it's lifetime from a device
different from the one holding the DMA firmware properties. Effectively,
in this case the struct device holding the firmware information about
the DMA channels is not the same as iio_dev->dev.parent (typical case).

While at it, namespace the buffer-dmaengine exports and update the
current user of these buffers.

Signed-off-by: Nuno Sa <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20240210-iio-backend-v11-4-f5242a5fb42a@analog.com
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>