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Date:   Tue, 21 Nov 2023 11:33:55 +0100
Message-ID: <874jhfo0oc.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 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.


Takashi

> > 3. Rename conflicting sysfs entries in drivers;
> >    e.g. color -> kb_color for hid-lg-g15 and system76_acpi
> > 
> > In either way, we'd break user-space (sysfs).
> 
> The new color attribute causing the conflict has only
> been in 6.6 so there likely aren't any users of it yet
> and since dropping it would be backported to 6.6.y
> there shouldn't be any future users of it either, since
> any 6.6 users presumably will use 6.6.y and not 6.6.0
> 
> > IMO, 2 would be the least harm, as the class sysfs entry was
> > introduced since 6.6.
> 
> Ack.
> 
> > I guess this is what Jean-Jacques suggested.
> 
> Right.
> 
> > But I'm not sure how important this new class sysfs entry is; it has
> > to be clarified from leds people who actually use / wanted the
> > feature.
> 
> If I have read the thread correctly it is not important the value
> it represents is used internally in the LED subsystem and userspace
> does not really need it.
> 
> Regards,
> 
> Hans
> 
> 
>