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

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Date:   Mon, 15 Nov 2021 14:39:59 +0100
From:   Arnd Bergmann <arnd@...nel.org>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:     Vinod Koul <vkoul@...nel.org>, 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>,
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Subject: Re: [PATCH 08/11] dmaengine: xilinx_dpdma: stop using slave_id field

On Mon, Nov 15, 2021 at 2:05 PM Laurent Pinchart
<laurent.pinchart@...asonboard.com> wrote:
> On Mon, Nov 15, 2021 at 01:38:07PM +0100, Arnd Bergmann wrote:
> > On Mon, Nov 15, 2021 at 12:49 PM Laurent Pinchart wrote:
> >
> > Right. I wonder if there is even a point in using the dmaengine API
> > in that case, I think for other single-purpose drivers we tend to just
> > integrate the functionality in the client driver. No point changing this
> > now of course, but it does feel odd.
>
> I agree, and that's what I would have done as well, if it wasn't for the
> fact that the DMA engine also supports a second client for audio. This
> isn't supported in upstream yet. We could still have created an ad-hoc
> solution, possibly based on the components framework, but the DMA engine
> subsystem wasn't a bad fit.

Ah, makes sense. In this case, I guess the data could have been
part of the DMA specifier after all, in a second cell after the
channel number.

        Arnd