Messages in this thread | | | From | Arnd Bergmann <> | Date | Mon, 15 Nov 2021 11:21:30 +0100 | Subject | Re: [PATCH 08/11] dmaengine: xilinx_dpdma: stop using slave_id field |
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On Mon, Nov 15, 2021 at 10:14 AM Laurent Pinchart <laurent.pinchart@ideasonboard.com> 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'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;
spin_lock_irqsave(&chan->lock, flags); if (chan->id <= ZYNQMP_DPDMA_VIDEO2 && config->peripheral_size == sizeof(*pconfig)) 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>
Thanks,
Arnd
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