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 partIs 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@ideasonboard.com