On Mon, 2022-03-28 at 19:39 +0100, Paul Cercueil wrote: > Hi Jonathan, > > Le lun., mars 28 2022 at 18:24:09 +0100, Jonathan Cameron > <jic23@xxxxxxxxxx> a écrit : > > On Mon, 7 Feb 2022 12:59:23 +0000 > > Paul Cercueil <paul@xxxxxxxxxxxxxxx> wrote: > > > > > 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. > > > > > > The .space_available() callback can return the exact same value > > > as > > > the > > > .data_available() callback for input buffers, since in both > > > cases we > > > count the exact same thing (the number of bytes in each > > > available > > > block). > > > > > > 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. > > > > > > v2: - 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() > > > > > > Signed-off-by: Paul Cercueil <paul@xxxxxxxxxxxxxxx> > > > Reviewed-by: Alexandru Ardelean <ardeleanalex@xxxxxxxxx> > > One comment inline. > > > > I'd be tempted to queue this up with that fixed, but do we have > > any users? Even though it's trivial I'm not that keen on code > > upstream well in advance of it being used. > > There's a userspace user in libiio. On the kernel side we do have > drivers that use it in ADI's downstream kernel, that we plan to > upstream in the long term (but it can take some time, as we need to > upstream other things first, like JESD204B support). > > You mean, users for DMA output buffers? If so, I have on my queue to add the dac counterpart of this one: https://elixir.bootlin.com/linux/latest/source/drivers/iio/adc/adi-axi-adc.c Which is a user of DMA buffers. Though this one does not depend on JESD204, I suspect it will also be a tricky process mainly because I think there are major issues on how things are done right now (on the ADC driver). But yeah, not a topic here and I do plan to first start the discussion on the mailing list before starting developing (hopefully in the coming weeks)... - Nuno Sá
