linux-kernel - Re: [PATCH v2] dmaengine: Create symlinks between DMA channels and slaves

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Date:   Mon, 27 Jan 2020 10:38:28 +0530
From:   Vinod Koul <vkoul@...nel.org>
To:     Peter Ujfalusi <peter.ujfalusi@...com>
Cc:     Geert Uytterhoeven <geert@...ux-m68k.org>,
        Dan Williams <dan.j.williams@...el.com>,
        dmaengine@...r.kernel.org,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] dmaengine: Create symlinks between DMA channels and
 slaves

On 24-01-20, 09:31, Peter Ujfalusi wrote:
> Vinod, Geert,
> 
> On 24/01/2020 8.13, Vinod Koul wrote:
> > On 22-01-20, 15:10, Vinod Koul wrote:
> > 
> >> I like the idea of adding this in debugfs and giving more info, I would
> >> actually love to add bytes_transferred and few more info (descriptors
> >> submitted etc) to it...
> >>
> >>>> This way we will have all the information in one place, easy to look up
> >>>> and you don't need to manage symlinks dynamically, just check all
> >>>> channels if they have slave_device/name when they are in_use (in_use w/o
> >>>> slave_device is 'non slave')
> >>>>
> >>>> Some drivers are requesting and releasing the DMA channel per transfer
> >>>> or when they are opened/closed or other variations.
> >>>>
> >>>>> What do other people think?
> >>>
> >>> Vinod: do you have some guidance for your minions? ;-)
> >>
> >>
> >> That said, I am not against merging this patch while we add more
> >> (debugfs)... So do my minions agree or they have better ideas :-)
> > 
> > So no new ideas, I am going to apply this and queue for 5.6, something
> > is better than nothing.
> 
> My only issue with the symlink is that it is created/removed on some
> setups quite frequently as they request/release channel per transfer or
> open/close.
> It might be a small hit in performance, but it is going to be for them.
> 
> > And I am looking forward for debugfs to give better picture, volunteers?
> 
> Well, I still feel that the debugfs can give better view in one place
> and in production it can be disabled to save few bytes per channel and
> code is not complied in.
> 
> If we have the debugfs we can remove some of the sysfs devices files
> probably.

Sure I dont mind if we move to something better :) We went from zero to
something and can do better!

Thanks

-- 
~Vinod