linux-kernel - [PATCH] hwmon: (pwm-fan) Ensure the fan going on in .probe()

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: Windows password security audit tool. GUI, reports in PDF.

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

Date:   Tue, 30 Nov 2021 17:22:12 +0800
From:   Billy Tsai <billy_tsai@...eedtech.com>
To:     <b.zolnierkie@...sung.com>, <jdelvare@...e.com>,
        <linux@...ck-us.net>, <u.kleine-koenig@...gutronix.de>,
        <linux-hwmon@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC:     <BMC-SW@...eedtech.com>, <stable@...r.kernel.org>
Subject: [PATCH] hwmon: (pwm-fan) Ensure the fan going on in .probe()

Before commit 86585c61972f ("hwmon: (pwm-fan) stop using legacy
PWM functions and some cleanups") pwm_apply_state() was called
unconditionally in pwm_fan_probe(). In this commit this direct
call was replaced by a call to __set_pwm(ct, MAX_PWM) which
however is a noop if ctx->pwm_value already matches the value to
set.
After probe the fan is supposed to run at full speed, and the
internal driver state suggests it does, but this isn't asserted
and depending on bootloader and pwm low-level driver, the fan
might just be off.
So drop setting pwm_value to MAX_PWM to ensure the check in
__set_pwm doesn't make it exit early and the fan goes on as
intended.

Cc: stable@...r.kernel.org
Fixes: 86585c61972f ("hwmon: (pwm-fan) stop using legacy PWM functions and some cleanups")
Signed-off-by: Billy Tsai <billy_tsai@...eedtech.com>
---
 drivers/hwmon/pwm-fan.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/drivers/hwmon/pwm-fan.c b/drivers/hwmon/pwm-fan.c
index 17518b4cab1b..f12b9a28a232 100644
--- a/drivers/hwmon/pwm-fan.c
+++ b/drivers/hwmon/pwm-fan.c
@@ -336,8 +336,6 @@ static int pwm_fan_probe(struct platform_device *pdev)
 			return ret;
 	}

-	ctx->pwm_value = MAX_PWM;
-
 	pwm_init_state(ctx->pwm, &ctx->pwm_state);

 	/*
-- 
2.25.1