Re: [PATCH] iio: buffer-dmaengine: adjust `bytes_used` with residue info

[Jonathan Cameron <jic23@kernel.org>]

On Wed, 26 Aug 2020 09:36:39 +0300
Alexandru Ardelean <ardeleanalex@gmail.com> wrote:

> On Wed, Aug 26, 2020 at 8:22 AM Lars-Peter Clausen <lars@metafoo.de> wrote:
> >
> > From: Alexandru Ardelean <alexandru.ardelean@analog.com>
> >
> > A transfer may fall shorter than the bytes in the block.
> > This information is available in the residue from the DMA engine, so we can
> > compute actual `bytes_used` with that by subtracting the residue.
> >  
> 
> This was in my pipeline as well [obviously].
> Thanks :)
> 
> > Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
> > Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>

"smells" like a fix.  Is it?  Or are we looking at something that
only matters for some future hardware, or an optmization?

If it's a fix, where is the fixes tag?

Thanks, 

Jonathan

> > ---
> >  drivers/iio/buffer/industrialio-buffer-dmaengine.c | 6 ++++--
> >  1 file changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/iio/buffer/industrialio-buffer-dmaengine.c b/drivers/iio/buffer/industrialio-buffer-dmaengine.c
> > index 6dedf12b69a4..5789bda0745b 100644
> > --- a/drivers/iio/buffer/industrialio-buffer-dmaengine.c
> > +++ b/drivers/iio/buffer/industrialio-buffer-dmaengine.c
> > @@ -45,7 +45,8 @@ static struct dmaengine_buffer *iio_buffer_to_dmaengine_buffer(
> >         return container_of(buffer, struct dmaengine_buffer, queue.buffer);
> >  }
> >
> > -static void iio_dmaengine_buffer_block_done(void *data)
> > +static void iio_dmaengine_buffer_block_done(void *data,
> > +               const struct dmaengine_result *result)
> >  {
> >         struct iio_dma_buffer_block *block = data;
> >         unsigned long flags;
> > @@ -53,6 +54,7 @@ static void iio_dmaengine_buffer_block_done(void *data)
> >         spin_lock_irqsave(&block->queue->list_lock, flags);
> >         list_del(&block->head);
> >         spin_unlock_irqrestore(&block->queue->list_lock, flags);
> > +       block->bytes_used -= result->residue;
> >         iio_dma_buffer_block_done(block);
> >  }
> >
> > @@ -74,7 +76,7 @@ static int iio_dmaengine_buffer_submit_block(struct iio_dma_buffer_queue *queue,
> >         if (!desc)
> >                 return -ENOMEM;
> >
> > -       desc->callback = iio_dmaengine_buffer_block_done;
> > +       desc->callback_result = iio_dmaengine_buffer_block_done;
> >         desc->callback_param = block;
> >
> >         cookie = dmaengine_submit(desc);
> > --
> > 2.20.1
> >