linux-kernel - Re: [PATCH 08/11] dmaengine: xilinx_dpdma: stop using slave

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Date:   Tue, 16 Nov 2021 09:58:54 +0530
From:   Vinod Koul <vkoul@...nel.org>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Arnd Bergmann <arnd@...db.de>, Andy Gross <agross@...nel.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Baolin Wang <baolin.wang7@...il.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Chunyan Zhang <zhang.lyra@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Hyun Kwon <hyun.kwon@...inx.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        Jon Hunter <jonathanh@...dia.com>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Laxman Dewangan <ldewangan@...dia.com>,
        Manivannan Sadhasivam <mani@...nel.org>,
        Mark Brown <broonie@...nel.org>,
        Michal Simek <michal.simek@...inx.com>,
        Nicolas Saenz Julienne <nsaenz@...nel.org>,
        Orson Zhai <orsonzhai@...il.com>,
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Subject: Re: [PATCH 08/11] dmaengine: xilinx_dpdma: stop using slave_id field

On 15-11-21, 11:21, Arnd Bergmann wrote:
> On Mon, Nov 15, 2021 at 10:14 AM Laurent Pinchart
> <laurent.pinchart@...asonboard.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.

I would feel this is still not use for the peripheral_config, but lets
keep it to get rid of slave_id.

Also, I would be better if this was moved to DT as the next cell, don't
recall why that was not done/feasible.

-- 
~Vinod