Re: [PATCH v2] backlight: pwm_bl: Fix uninitialized variable
From: Lee Jones <hidden>
Date: 2018-07-23 07:23:50
Also in:
dri-devel, linux-pwm, lkml
On Thu, 19 Jul 2018, Daniel Thompson wrote:
Currently, if the DT does not define num-interpolated-steps then
num_steps is undefined and the interpolation code will deploy randomly.
Fix this.
Additionally fix a small grammar error that was identified and
tighten up return code checking of DT properties, both of which came
up during review of this patch.
Fixes: 573fe6d1c25c ("backlight: pwm_bl: Linear interpolation between
brightness-levels")
Reported-by: Marcel Ziswiler <redacted>
Signed-off-by: Daniel Thompson <redacted>
Tested-by: Marcel Ziswiler <redacted>
---
Notes:
v2:
- Simplify SoB chain (with Marcel's permission)
- Separate complex if statement and make other similar calls use same
return code checking approach
- Tidy up comment formatting and fix pre-existing grammar error
drivers/video/backlight/pwm_bl.c | 25 ++++++++++++-------------
1 file changed, 12 insertions(+), 13 deletions(-)I'm hesitant to provide feedback on this, as I feel as though I've messed you around enough, however ... ;)
quoted hunk ↗ jump to hunk
diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c index 9ee4c1b735b2..f7799f62fea0 100644 --- a/drivers/video/backlight/pwm_bl.c +++ b/drivers/video/backlight/pwm_bl.c@@ -284,30 +284,29 @@ static int pwm_backlight_parse_dt(struct device *dev, ret = of_property_read_u32_array(node, "brightness-levels", data->levels, data->max_brightness); - if (ret < 0) + if (!ret) return ret; ret = of_property_read_u32(node, "default-brightness-level", &value); - if (ret < 0) + if (!ret) return ret;
Just FYI (it didn't even make it to 'nit' status), this should really be done in a separate patch since it is unrelated to the rest of the patch.
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.
+ * 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);
-
- /*
- * 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) {
+ ret = of_property_read_u32(node, "num-interpolated-steps",
+ &num_steps);
+ if (!ret || num_steps) {
Not sure if it's even possible for of_property_read_u32() to fail AND
still populate num_steps, however this check makes it sound like that's
okay. Is that correct?
I can't help but think that this all 'just goes away' if you
pre-initialise num_steps. I wouldn't let the "do not initialise too
far away from the code using variable" affect this. However, if
you're insistent, perhaps consider moving the declaration to just
below:
if (data->max_brightness > 0) {
+ /*
+ * Make sure that there are at least two entries in
+ * the brightness-levels table, otherwise we can't
+ * interpolate between two points.
+ */
if (data->max_brightness < 2) {
dev_err(dev, "can't interpolate\n");
return -EINVAL;-- Lee Jones [李琼斯] Linaro Services Technical Lead Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog