linux-kernel - Re: [PATCH] leds: rgb: leds-qcom-lpg: Only enable TRILED when LPG is used by LED

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <7732165a-4147-4917-b76a-1525aae13c25@oss.qualcomm.com>
Date: Fri, 14 Nov 2025 15:13:18 +0800
From: Fenglin Wu <fenglin.wu@....qualcomm.com>
To: Bjorn Andersson <andersson@...nel.org>
Cc: kernel@....qualcomm.com, Lee Jones <lee@...nel.org>,
        Pavel Machek <pavel@...nel.org>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        Subbaraman Narayanamurthy <subbaraman.narayanamurthy@....qualcomm.com>,
        Pavel Machek <pavel@....cz>, linux-leds@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] leds: rgb: leds-qcom-lpg: Only enable TRILED when LPG is
 used by LED


On 11/14/2025 12:58 PM, Bjorn Andersson wrote:
> If chan->in_use, then the channel is exposed as a LED and
> lpg_pwm_request() should have returned -EBUSY, so we should never reach
> lpg_pwm_apply()?

Yes, I agree.

Change is trying to ignore enabling TRILED channel when the LPG channel 
mapping to TRILED is not used for controlling the LED (not defining the 
LED child nodes).

So the fix should be just removing this line instead of adding the if check.

I will update it in patch v2.

>
> Why do you check chan->triled_mask? I guess we will still read/write the
> triled regiter, but don't make any changes if this is 0?
>
> Or is this the actual issue that you're fixing, that we read/write the
> registers when we shouldn't? If so this should be clarified in the
> commit message.

Yes, there was a case that a LPG channel mapping to TRILED is repurposed 
to control a fan, and it was seen that the BOB1 (supplies to TRILED) 
voltage bumped to higher voltage when the PWM channel was enabled.

>
> Regards,
> Bjorn