linux-kernel - Re: [PATCH v3 08/10] dmaengine: dw: Add dummy device

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Message-ID: <20200528203429.n23gi65zndfo4zti@mobilestation>
Date:   Thu, 28 May 2020 23:34:29 +0300
From:   Serge Semin <Sergey.Semin@...kalelectronics.ru>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
CC:     Serge Semin <fancer.lancer@...il.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Vinod Koul <vkoul@...nel.org>,
        Viresh Kumar <vireshk@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Arnd Bergmann <arnd@...db.de>,
        Rob Herring <robh+dt@...nel.org>, <linux-mips@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        dmaengine <dmaengine@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 08/10] dmaengine: dw: Add dummy device_caps callback

On Thu, May 28, 2020 at 11:29:16PM +0300, Andy Shevchenko wrote:
> On Thu, May 28, 2020 at 6:30 PM Serge Semin
> <Sergey.Semin@...kalelectronics.ru> wrote:
> >
> > On Thu, May 28, 2020 at 05:53:03PM +0300, Andy Shevchenko wrote:
> > > On Wed, May 27, 2020 at 01:50:19AM +0300, Serge Semin wrote:
> > > > Since some DW DMA controllers (like one installed on Baikal-T1 SoC) may
> > > > have non-uniform DMA capabilities per device channels, let's add
> > > > the DW DMA specific device_caps callback to expose that specifics up to
> > > > the DMA consumer. It's a dummy function for now. We'll fill it in with
> > > > capabilities overrides in the next commits.
> > >
> > > I think per se it is not worth to have it separated. Squash into the next one.
> >
> > bikeshadding?
> 
> Actually no.
> 
> > There is no any difference whether I add a dummy callback, then
> > fill it in in a following up patch, or have the callback added together
> > with some content. Let's see what Vinod thinks of it. Until then I'll stick with
> > the current solution.
> 
> The rule of thumb that we don't add dead code or code which is useless
> per se. Go ahead and provide it with some usefulness.

Actually yes. I've seen examples, which preparation patches first added
prototypes with empty functionality, that in follow-up patches have been
filled with a required code. I've seen Greg accepted such approach. So it's
absolutely normal and acceptable.

-Sergey

> 
> -- 
> With Best Regards,
> Andy Shevchenko