lkml.org 
[lkml]   [2018]   [Jul]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patches in this message
/
Date
From
SubjectRe: REGRESSION: [RESEND PATCH v3 1/4] backlight: pwm_bl: linear interpolation between brightness-levels
On Sat, Jul 14, 2018 at 03:08:17PM +0000, Marcel Ziswiler wrote:
> On Mon, 2018-04-09 at 10:33 +0200, Enric Balletbo i Serra wrote:
> > diff --git a/drivers/video/backlight/pwm_bl.c
> > b/drivers/video/backlight/pwm_bl.c
> > index 8e3f1245f5c5..f0a108ab570a 100644
> > --- a/drivers/video/backlight/pwm_bl.c
> > +++ b/drivers/video/backlight/pwm_bl.c
> > @@ -147,7 +147,11 @@ static int pwm_backlight_parse_dt(struct device
> > *dev,
> > struct platform_pwm_backlight_data
> > *data)
> > {
> > struct device_node *node = dev->of_node;
> > + unsigned int num_levels = 0;
> > + unsigned int levels_count;
> > + unsigned int num_steps;

num_steps is not initialized...


> > struct property *prop;
> > + unsigned int *table;
> > int length;
> > u32 value;
> > int ret;
> > @@ -167,6 +171,7 @@ static int pwm_backlight_parse_dt(struct device
> > *dev,
> > /* read brightness levels from DT property */
> > if (data->max_brightness > 0) {
> > size_t size = sizeof(*data->levels) * data-
> > >max_brightness;
> > + unsigned int i, j, n = 0;
> >
> > data->levels = devm_kzalloc(dev, size, GFP_KERNEL);
> > if (!data->levels)
> > @@ -184,6 +189,84 @@ static int pwm_backlight_parse_dt(struct device
> > *dev,
> > return ret;
> >
> > data->dft_brightness = value;
> > +
> > + /*
> > + * This property is optional, if is set enables
> > linear
> > + * interpolation between each of the values of
> > brightness levels
> > + * and creates a new pre-computed table.
> > + */
> > + of_property_read_u32(node, "num-interpolated-steps",
> > + &num_steps);

... this is not guaranteed to initialized num_steps ...

> > +
> > + /*
> > + * Make sure that there is at least two entries in
> > the
> > + * brightness-levels table, otherwise we can't
> > interpolate
> > + * between two points.
> > + */
> > + if (num_steps) {

... and we make a decision on it here.

Marcel: Can you try the following quick fix? It's untested on my side
but very simple...

From 6fa2fbeb017086147ac61981107a95cb8ae7b4e7 Mon Sep 17 00:00:00 2001
From: Daniel Thompson <daniel.thompson@linaro.org>
Date: Sun, 15 Jul 2018 08:49:05 +0100
Subject: [PATCH] backlight: pwm_bl: Fix uninitialized variable
Currently, if the DT does not define num-interpolated-steps then
num_steps is undefined meaning the interpolation code will deploy
randomly. Fix this.

Fixes: 573fe6d1c25c ("backlight: pwm_bl: Linear interpolation between
brightness-levels")
Reported-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
---
drivers/video/backlight/pwm_bl.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
index 9ee4c1b735b2..bdfcc0a71db1 100644
--- a/drivers/video/backlight/pwm_bl.c
+++ b/drivers/video/backlight/pwm_bl.c
@@ -250,7 +250,7 @@ static int pwm_backlight_parse_dt(struct device *dev,
struct device_node *node = dev->of_node;
unsigned int num_levels = 0;
unsigned int levels_count;
- unsigned int num_steps;
+ unsigned int num_steps = 0;
struct property *prop;
unsigned int *table;
int length;
--
2.17.1
\
 
 \ /
  Last update: 2018-07-15 22:07    [W:0.067 / U:0.296 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site