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Date:   Tue, 21 Nov 2023 15:26:21 +0100
Message-ID: <87fs0zmbci.wl-tiwai@suse.de>
From:   Takashi Iwai <tiwai@suse.de>
To:     Hans de Goede <hdegoede@redhat.com>
Cc:     Takashi Iwai <tiwai@suse.de>,
        Thorsten Leemhuis <regressions@leemhuis.info>,
        Jean-Jacques Hiblot <jjhiblot@traphandler.com>,
        Bagas Sanjaya <bagasdotme@gmail.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux Regressions <regressions@lists.linux.dev>,
        Linux LEDs <linux-leds@vger.kernel.org>,
        Tim Crawford <tcrawford@system76.com>,
        Jeremy Soller <jeremy@system76.com>,
        System76 Product Development <productdev@system76.com>,
        Lee Jones <lee@kernel.org>, Pavel Machek <pavel@ucw.cz>,
        Johannes =?ISO-8859-1?Q?Pe?= =?ISO-8859-1?Q?n=DFel?= 
        <johannes.penssel@gmail.com>
Subject: Re: Fwd: sysfs: cannot create duplicate filename .../system76_acpi::kbd_backlight/color
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On Tue, 21 Nov 2023 13:23:20 +0100,
Hans de Goede wrote:
> 
> Hi,
> 
> On 11/21/23 11:33, Takashi Iwai wrote:
> > On Tue, 21 Nov 2023 11:21:53 +0100,
> > Hans de Goede wrote:
> >>
> >> Hi,
> >>
> >> On 11/21/23 10:52, Takashi Iwai wrote:
> >>> On Tue, 21 Nov 2023 10:19:03 +0100,
> >>> Thorsten Leemhuis wrote:
> >>>>
> >>>> Takashi, Jean-Jacques Hiblot, Lee,
> >>>>
> >>>> On 20.11.23 14:53, Takashi Iwai wrote:
> >>>>> On Mon, 06 Nov 2023 14:19:08 +0100,
> >>>>> Bagas Sanjaya wrote:
> >>>>>> On Sat, Nov 04, 2023 at 01:01:56PM +0100, Jean-Jacques Hiblot wrote:
> >>>>>>> On 29/10/2023 02:48, Bagas Sanjaya wrote:
> >>>>>>>> On Thu, Oct 26, 2023 at 02:55:06PM +0700, Bagas Sanjaya wrote:
> >>>>>>>>> The culprit seems to be commit c7d80059b086c4986cd994a1973ec7a5d75f8eea, which introduces a new 'color' attribute for led sysfs class devices. The problem is that the system76-acpi platform driver tries to create the exact same sysfs attribute itself for the system76_acpi::kbd_backlight device, leading to the conflict. For testing purposes, I've just rebuilt the kernel with the system76-apci color attribute renamed to kb_color, and that fixes the issue.
> >>>>>>>>
> >>>>>>>> Jean-Jacques Hiblot, would you like to take a look on this regression,
> >>>>>>>> since you authored the culprit?
> >>>>>
> >>>>>>> The offending commit stores the color in struct led_classdev and exposes it
> >>>>>>> via sysfs. It was part of a series that create a RGB leds from multiple
> >>>>>>> single-color LEDs. for this series, we need the color information but we
> >>>>>>> don't really need to expose it it via sysfs. In order to fix the issue, we
> >>>>>>> can remove the 'color' attribute from the sysfs.
> >>>>>>
> >>>>>> OK, see you in the patch!
> >>>>>
> >>>>> Is there a patch available?
> >>>>
> >>>> Not that I know of. Could not find anything on lore either.
> >>>>
> >>>>> This bug hits for a few Logitech keyboard models, too, and it makes
> >>>>> 6.6 kernel unsable for them, as hid-lg-g15 driver probe fails due to
> >>>>> this bug:
> >>>>>   https://bugzilla.kernel.org/show_bug.cgi?id=218155
> >>>>>
> >>>>> We need a quick fix for 6.6.x.
> >>>>
> >>>> Given that Jean-Jacques Hiblot (the author of the culprit) and Lee (who
> >>>> committed it and sent it to Linus) know about this for a while already
> >>>> without doing anything about it, I wonder if someone should just send a
> >>>> revert to Linus (unless of course that is likely to introduce a
> >>>> regression on its own).
> >>>>
> >>>> Takashi, could you maybe do this, unless a fix shows up real soon?
> >>>
> >>> I can, but we need to decide which way to go.
> >>> There are several options:
> >>>
> >>> 1. Revert the commit c7d80059b086;
> >>>    this drops led class color sysfs entries.  Also the store of
> >>>    led_cdev->color from fwnode is dropped, too.
> >>>
> >>> 2. Drop only led class color sysfs entries;
> >>>    a partial revert of c7d80059b086 above
> >>
> >> AFAIK further up in the thread (or a related thread) there
> >> already was consensus to do this. Someone just needs to
> >> write the patch.
> > 
> > Well, is there any user of this new led_classdev.color field?
> > The value read from fwnode is stored there, but as far as I see, there
> > seems no real user, so far.  If it's still unused, we can do the whole
> > revert -- which is cleaner.
> 
> I honestly don't know. I've mostly just been reading along. I think
> there may be some future in kernel use planned (not sure at all though).
> 
> If there are no current in kernel users then I agree we should just
> go with a full revert now to fix the regression. If some later
> in kernel users do come along then they can always re-introduce
> the change minus the sysfs attr addition.

Sounds reasonable.
OK, let me pitch the revert patch.


thanks,

Takashi