Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:7 as permitted sender) client-ip=2620:137:e000::3:7;
Message-ID: <37f6aa8e-8cab-4194-8493-8e39819ed608@redhat.com>
Date:   Tue, 21 Nov 2023 13:23:20 +0100
MIME-Version: 1.0
User-Agent: Mozilla Thunderbird
Subject: Re: Fwd: sysfs: cannot create duplicate filename
 .../system76_acpi::kbd_backlight/color
Content-Language: en-US, nl
To:     Takashi Iwai <tiwai@suse.de>
Cc:     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>,
        =?UTF-8?Q?Johannes_Pen=C3=9Fel?= <johannes.penssel@gmail.com>
References: <b5646db3-acff-45aa-baef-df3f660486fb@gmail.com>
 <ZT25-gUmLl8MPk93@debian.me>
 <dc6264c4-d551-4913-a51b-72c22217f15a@traphandler.com>
 <ZUjnzB2RL2iLzIQG@debian.me> <87sf50pm34.wl-tiwai@suse.de>
 <b9d4ab02-fe49-48ab-bf74-0c7a578e891a@leemhuis.info>
 <87edgjo2kr.wl-tiwai@suse.de>
 <ae77198c-ae7b-4988-8b5b-824260b28e84@redhat.com>
 <874jhfo0oc.wl-tiwai@suse.de>
From:   Hans de Goede <hdegoede@redhat.com>
In-Reply-To: <874jhfo0oc.wl-tiwai@suse.de>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
Precedence: bulk

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.

Regards,

Hans