On Mon, 7 Feb 2022 12:59:21 +0000 Paul Cercueil paul@crapouillou.net wrote:
Hi Jonathan,
This is the V2 of my patchset that introduces a new userspace interface based on DMABUF objects to complement the fileio API, and adds write() support to the existing fileio API.
Hi Paul,
It's been a little while. Perhaps you could summarize the various view points around the appropriateness of using DMABUF for this? I appreciate it is a tricky topic to distil into a brief summary but I know I would find it useful even if no one else does!
Thanks,
Jonathan
Changes since v1:
- the patches that were merged in v1 have been (obviously) dropped from this patchset;
- the patch that was setting the write-combine cache setting has been dropped as well, as it was simply not useful.
- [01/12]:
- Only remove the outgoing queue, and keep the incoming queue, as we want the buffer to start streaming data as soon as it is enabled.
- Remove IIO_BLOCK_STATE_DEQUEUED, since it is now functionally the same as IIO_BLOCK_STATE_DONE.
- [02/12]:
- Fix block->state not being reset in iio_dma_buffer_request_update() for output buffers.
- Only update block->bytes_used once and add a comment about why we update it.
- Add a comment about why we're setting a different state for output buffers in iio_dma_buffer_request_update()
- Remove useless cast to bool (!!) in iio_dma_buffer_io()
- [05/12]: Only allow the new IOCTLs on the buffer FD created with IIO_BUFFER_GET_FD_IOCTL().
- [12/12]:
- Explicitly state that the new interface is optional and is not implemented by all drivers.
- The IOCTLs can now only be called on the buffer FD returned by IIO_BUFFER_GET_FD_IOCTL.
- Move the page up a bit in the index since it is core stuff and not driver-specific.
The patches not listed here have not been modified since v1.
Cheers, -Paul
Alexandru Ardelean (1): iio: buffer-dma: split iio_dma_buffer_fileio_free() function
Paul Cercueil (11): iio: buffer-dma: Get rid of outgoing queue iio: buffer-dma: Enable buffer write support iio: buffer-dmaengine: Support specifying buffer direction iio: buffer-dmaengine: Enable write support iio: core: Add new DMABUF interface infrastructure iio: buffer-dma: Use DMABUFs instead of custom solution iio: buffer-dma: Implement new DMABUF based userspace API iio: buffer-dmaengine: Support new DMABUF based userspace API iio: core: Add support for cyclic buffers iio: buffer-dmaengine: Add support for cyclic buffers Documentation: iio: Document high-speed DMABUF based API
Documentation/driver-api/dma-buf.rst | 2 + Documentation/iio/dmabuf_api.rst | 94 +++ Documentation/iio/index.rst | 2 + drivers/iio/adc/adi-axi-adc.c | 3 +- drivers/iio/buffer/industrialio-buffer-dma.c | 610 ++++++++++++++---- .../buffer/industrialio-buffer-dmaengine.c | 42 +- drivers/iio/industrialio-buffer.c | 60 ++ include/linux/iio/buffer-dma.h | 38 +- include/linux/iio/buffer-dmaengine.h | 5 +- include/linux/iio/buffer_impl.h | 8 + include/uapi/linux/iio/buffer.h | 30 + 11 files changed, 749 insertions(+), 145 deletions(-) create mode 100644 Documentation/iio/dmabuf_api.rst