From: <gregkh@linuxfoundation.org>
To: dbasehore@chromium.org, alexander.levin@verizon.com,
briannorris@chromium.org, gregkh@linuxfoundation.org,
lee.jones@linaro.org, thierry.reding@gmail.com
Cc: <stable@vger.kernel.org>, <stable-commits@vger.kernel.org>
Subject: Patch "backlight: pwm_bl: Fix overflow condition" has been added to the 4.14-stable tree
Date: Wed, 20 Dec 2017 18:20:08 +0100 [thread overview]
Message-ID: <151379040816533@kroah.com> (raw)
This is a note to let you know that I've just added the patch titled
backlight: pwm_bl: Fix overflow condition
to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
backlight-pwm_bl-fix-overflow-condition.patch
and it can be found in the queue-4.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.
>From foo@baz Wed Dec 20 18:17:52 CET 2017
From: Derek Basehore <dbasehore@chromium.org>
Date: Tue, 29 Aug 2017 13:34:34 -0700
Subject: backlight: pwm_bl: Fix overflow condition
From: Derek Basehore <dbasehore@chromium.org>
[ Upstream commit 5d0c49acebc9488e37db95f1d4a55644e545ffe7 ]
This fixes an overflow condition that can happen with high max
brightness and period values in compute_duty_cycle. This fixes it by
using a 64 bit variable for computing the duty cycle.
Signed-off-by: Derek Basehore <dbasehore@chromium.org>
Acked-by: Thierry Reding <thierry.reding@gmail.com>
Reviewed-by: Brian Norris <briannorris@chromium.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/video/backlight/pwm_bl.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
--- a/drivers/video/backlight/pwm_bl.c
+++ b/drivers/video/backlight/pwm_bl.c
@@ -79,14 +79,17 @@ static void pwm_backlight_power_off(stru
static int compute_duty_cycle(struct pwm_bl_data *pb, int brightness)
{
unsigned int lth = pb->lth_brightness;
- int duty_cycle;
+ u64 duty_cycle;
if (pb->levels)
duty_cycle = pb->levels[brightness];
else
duty_cycle = brightness;
- return (duty_cycle * (pb->period - lth) / pb->scale) + lth;
+ duty_cycle *= pb->period - lth;
+ do_div(duty_cycle, pb->scale);
+
+ return duty_cycle + lth;
}
static int pwm_backlight_update_status(struct backlight_device *bl)
Patches currently in stable-queue which might be from dbasehore@chromium.org are
queue-4.14/backlight-pwm_bl-fix-overflow-condition.patch
reply other threads:[~2017-12-20 17:20 UTC|newest]
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