linux-kernel - Duplicate TI EDMA debugfs registration

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Message-ID: <CAMuHMdXSSVMK_ohHrna8DWy7KU697mnsVHhBrzNMzs1d07J=qQ@mail.gmail.com>
Date: Tue, 12 Aug 2025 15:32:46 +0200
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Peter Ujfalusi <peter.ujfalusi@...il.com>, Aaro Koskinen <aaro.koskinen@....fi>, 
	Andreas Kemnade <andreas@...nade.info>, Kevin Hilman <khilman@...libre.com>, 
	Roger Quadros <rogerq@...nel.org>, Tony Lindgren <tony@...mide.com>, Vinod Koul <vkoul@...nel.org>, 
	Matti Vaittinen <mazziesaccount@...il.com>
Cc: dmaengine <dmaengine@...r.kernel.org>, 
	"open list:TI ETHERNET SWITCH DRIVER (CPSW)" <linux-omap@...r.kernel.org>, 
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Duplicate TI EDMA debugfs registration

Hi,

The TI EDMA driver registers two DMA engines:
https://elixir.bootlin.com/linux/v6.16/source/drivers/dma/ti/edma.c#L2525

This was fine when support for the second engine was introduced[1],
as it predated debugfs support for DMA engines[2].
However, both instances contain a pointer to the same physical device,
hence when the debugfs directory is created for the second engine at
https://elixir.bootlin.com/linux/v6.16/source/drivers/dma/dmaengine.c#L71,
it fails.

E.g. on BeagleBone Black:

    debugfs: '49000000.dma' already exists in 'dmaengine'

Note that this is not really a new problem, but it was brought to my
attention because the printed error message was changed in v6.17-rc1[3].
Before, it printed:

    debugfs: Directory '49000000.dma' with parent 'dmaengine' already present!

Thanks!

[1] 1be5336bc7ba050e ("dmaengine: edma: New device tree binding")
[2] 26cf132de6f79c06 ("dmaengine: Create debug directories for DMA devices")
[3] 59200f4526748158 ("new helper: simple_start_creating()")

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