linux-kernel - Re: [PATCH 2/8 v2] Documentation: bindings: k3dma: Add binding for dma-avail-chan

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Date:   Fri, 4 Jan 2019 20:39:34 -0800
From:   John Stultz <john.stultz@...aro.org>
To:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Cc:     lkml <linux-kernel@...r.kernel.org>, Vinod Koul <vkoul@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Tanglei Han <hantanglei@...wei.com>,
        Zhuangluan Su <suzhuangluan@...ilicon.com>,
        Ryan Grachek <ryan@...ted.us>, dmaengine@...r.kernel.org,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>
Subject: Re: [PATCH 2/8 v2] Documentation: bindings: k3dma: Add binding for dma-avail-chan

On Fri, Jan 4, 2019 at 8:00 PM Manivannan Sadhasivam
<manivannan.sadhasivam@...aro.org> wrote:
>
> Hi John,
>
> On Fri, Jan 04, 2019 at 12:56:22PM -0800, John Stultz wrote:
> > Some dma channels can be reserved for secure mode or other
> > hardware on the SoC, so provide a binding for a bitmask
> > listing the available channels for the kernel to use.
> >
> > Cc: Vinod Koul <vkoul@...nel.org>
> > Cc: Rob Herring <robh+dt@...nel.org>
> > Cc: Mark Rutland <mark.rutland@....com>
> > Cc: Tanglei Han <hantanglei@...wei.com>
> > Cc: Zhuangluan Su <suzhuangluan@...ilicon.com>
> > Cc: Ryan Grachek <ryan@...ted.us>
> > Cc: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> > Cc: dmaengine@...r.kernel.org
> > Cc: devicetree@...r.kernel.org
> > Signed-off-by: John Stultz <john.stultz@...aro.org>
> > ---
> >  Documentation/devicetree/bindings/dma/k3dma.txt | 3 +++
> >  1 file changed, 3 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/dma/k3dma.txt b/Documentation/devicetree/bindings/dma/k3dma.txt
> > index 10a2f15..1c466c1 100644
> > --- a/Documentation/devicetree/bindings/dma/k3dma.txt
> > +++ b/Documentation/devicetree/bindings/dma/k3dma.txt
> > @@ -14,6 +14,9 @@ Required properties:
> >               have specific request line
> >  - clocks: clock required
> >
> > +Optional properties:
> > +- dma-avail-chan: Bitmask of available physical channels
> > +
>
> This property looks too generic. Since this is specific to HiSi SoCs,
> this could be "hisi-dma-avail-chan"?

I'm fine to change it, but I'm not sure I fully understand the
rational. Can you help me understand?
Are device node-binding names supposed to have global scope? I assumed
the node property names are basically scoped to the entry?
Further, having some dma channels be reserved doesn't seem to be too
unique a concept, so I'm not sure what we gain long term by prefixing
it?

thanks
-john