Hi Arnd, On Mon, Nov 15, 2021 at 11:21:30AM +0100, Arnd Bergmann wrote: > On Mon, Nov 15, 2021 at 10:14 AM Laurent Pinchart wrote: > > On Mon, Nov 15, 2021 at 09:54:00AM +0100, Arnd Bergmann wrote: > > > @@ -1285,11 +1287,13 @@ static int xilinx_dpdma_config(struct dma_chan *dchan, > > > spin_lock_irqsave(&chan->lock, flags); > > > > > > /* > > > - * Abuse the slave_id to indicate that the channel is part of a video > > > - * group. > > > + * Abuse the peripheral_config to indicate that the channel is part > > > > Is it still an abuse, or is this now the right way to pass custom data > > to the DMA engine driver ? > > It doesn't make the driver any more portable, but it's now being > more explicit about it. As far as I can tell, this is the best way > to pass data that cannot be expressed through the regular interfaces > in DT and the dmaengine API. > > Ideally there would be a generic way to pass this flag, but I couldn't > figure out what this is actually doing, or whether there is a better > way. Maybe Vinod has an idea. I don't think we need a generic API in this case. The DMA engine is specific to the display device, I don't foresee a need to mix-n-match. > I'll change s/Abuse/Use/ for the moment until I get a definite answer. > > > > + * of a video group. > > > */ > > > - if (chan->id <= ZYNQMP_DPDMA_VIDEO2) > > > - chan->video_group = config->slave_id != 0; > > > + pconfig = config->peripheral_config; > > > > This could be moved to the variable declaration above, up to you. > > I considered that but since it doesn't fit in a normal 80-column > line, it seemed best to do it here. > > > > + if (chan->id <= ZYNQMP_DPDMA_VIDEO2 && > > > + config->peripheral_size == sizeof(*pconfig)) > > > > Silently ignoring a size mismatch isn't nice. Could we validate the size > > at the beginning of the function and return an error ? > > Yes, good idea. Since this would mean a bug in another driver, > I'll add a WARN_ON() as well to make it clear which driver caused it. > This is what I have now, let me know if you have any further suggestions: > > /* > * Use the peripheral_config to indicate that the channel is part > * of a video group. This requires matching use of the custom > * structure in each driver. > */ > pconfig = config->peripheral_config; > if (WARN_ON(config->peripheral_size != 0 && > config->peripheral_size != sizeof(*pconfig))) > return -EINVAL; How about if (WARN_ON(config->peripheral_config && config->peripheral_size != sizeof(*pconfig))) > > spin_lock_irqsave(&chan->lock, flags); > if (chan->id <= ZYNQMP_DPDMA_VIDEO2 && > config->peripheral_size == sizeof(*pconfig)) And here you can test pconfig != NULL. > chan->video_group = pconfig->video_group; > spin_unlock_irqrestore(&chan->lock, flags); > > return 0; > > > With these issues addressed, > > > > Reviewed-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx> -- Regards, Laurent Pinchart
