Re: [PATCH v2 00/12] iio: buffer-dma: write() and new DMABUF based API

Jonathan Cameron
2022-02-13T18:39:40Z

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
>