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

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Date:   Thu, 30 Jan 2020 11:47:06 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Marek Szyprowski <m.szyprowski@...sung.com>
Cc:     Geert Uytterhoeven <geert+renesas@...der.be>,
        Vinod Koul <vkoul@...nel.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

Hi Marek,

On Thu, Jan 30, 2020 at 11:33 AM Marek Szyprowski
<m.szyprowski@...sung.com> wrote:
> On 30.01.2020 09:30, Geert Uytterhoeven wrote:
> > On Wed, Jan 29, 2020 at 6:47 PM Marek Szyprowski
> > <m.szyprowski@...sung.com> wrote:
> >> On 17.01.2020 16:30, Geert Uytterhoeven wrote:
> >>> Currently it is not easy to find out which DMA channels are in use, and
> >>> which slave devices are using which channels.
> >>>
> >>> Fix this by creating two symlinks between the DMA channel and the actual
> >>> slave device when a channel is requested:
> >>>     1. A "slave" symlink from DMA channel to slave device,
> >>>     2. A "dma:<name>" symlink slave device to DMA channel.
> >>> When the channel is released, the symlinks are removed again.
> >>> The latter requires keeping track of the slave device and the channel
> >>> name in the dma_chan structure.
> >>>
> >>> Note that this is limited to channel request functions for requesting an
> >>> exclusive slave channel that take a device pointer (dma_request_chan()
> >>> and dma_request_slave_channel*()).
> >>>
> >>> Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>
> >>> Tested-by: Niklas Söderlund <niklas.soderlund@...natech.se>
> >> This patch breaks booting on almost all Exynos based boards:
> >>
> >> https://lore.kernel.org/linux-samsung-soc/20200129161113.GE3928@sirena.org.uk/T/#u
> > Sorry for the breakage.
>
> No problem, that's why we have linux-next.

Not really: by that time it had been upstream for 2 days :-(

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds