From: Daniel Thompson <hidden> Date: 2018-07-16 21:03:20
Currently, if the DT does not define num-interpolated-steps then
num_steps is undefined and the interpolation code will deploy randomly.
Fix this.
Fixes: 573fe6d1c25c ("backlight: pwm_bl: Linear interpolation between
brightness-levels")
Reported-by: Marcel Ziswiler <redacted>
Signed-off-by: Daniel Thompson <redacted>
Signed-off-by: Marcel Ziswiler <redacted>
Tested-by: Marcel Ziswiler <redacted>
---
drivers/video/backlight/pwm_bl.c | 17 ++++++++---------
1 file changed, 8 insertions(+), 9 deletions(-)
From: Lee Jones <hidden> Date: 2018-07-18 08:09:19
On Mon, 16 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.
Fixes: 573fe6d1c25c ("backlight: pwm_bl: Linear interpolation between
brightness-levels")
Reported-by: Marcel Ziswiler <redacted>
Signed-off-by: Daniel Thompson <redacted>
Signed-off-by: Marcel Ziswiler <redacted>
This line is confusing. Did you guys author this patch together?
My guess is that this line should be dropped and the RB and TB tags
should remain? If it was reviewed too, perhaps an AB too?
@@ -299,15 +299,14 @@ static int pwm_backlight_parse_dt(struct device *dev,*interpolationbetweeneachofthevaluesofbrightnesslevels*andcreatesanewpre-computedtable.*/-of_property_read_u32(node,"num-interpolated-steps",-&num_steps);--/*-*Makesurethatthereisatleasttwoentriesinthe-*brightness-levelstable,otherwisewecan'tinterpolate-*betweentwopoints.-*/-if(num_steps){+if((of_property_read_u32(node,"num-interpolated-steps",+&num_steps)=0)&&num_steps){
This is pretty ugly, and isn't it suffering from over-bracketing? My
suggestion would be to break out the invocation of
of_property_read_u32() from the if and test only the result.
of_property_read_u32(node, "num-interpolated-steps", &num_steps);
if (!ret && num_steps) {
I haven't checked the underling code, but is it even feasible for
of_property_read_u32() to not succeed AND for num_steps to be set?
If not, the check for !ret if superfluous and you can drop it.
+ /*
+ * Make sure that there is at least two entries in the
s/is/are/
+ * brightness-levels table, otherwise we can't
+ * interpolate
Why break the line here?
+ * 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
From: Lee Jones <hidden> Date: 2018-07-18 08:12:59
On Wed, 18 Jul 2018, Lee Jones wrote:
On Mon, 16 Jul 2018, Daniel Thompson wrote:
quoted
Currently, if the DT does not define num-interpolated-steps then
num_steps is undefined and the interpolation code will deploy randomly.
Fix this.
Fixes: 573fe6d1c25c ("backlight: pwm_bl: Linear interpolation between
brightness-levels")
Reported-by: Marcel Ziswiler <redacted>
Signed-off-by: Daniel Thompson <redacted>
Signed-off-by: Marcel Ziswiler <redacted>
This line is confusing. Did you guys author this patch together?
My guess is that this line should be dropped and the RB and TB tags
should remain? If it was reviewed too, perhaps an AB too?
@@ -299,15 +299,14 @@ static int pwm_backlight_parse_dt(struct device *dev,*interpolationbetweeneachofthevaluesofbrightnesslevels*andcreatesanewpre-computedtable.*/-of_property_read_u32(node,"num-interpolated-steps",-&num_steps);--/*-*Makesurethatthereisatleasttwoentriesinthe-*brightness-levelstable,otherwisewecan'tinterpolate-*betweentwopoints.-*/-if(num_steps){+if((of_property_read_u32(node,"num-interpolated-steps",+&num_steps)=0)&&num_steps){
This is pretty ugly, and isn't it suffering from over-bracketing? My
suggestion would be to break out the invocation of
of_property_read_u32() from the if and test only the result.
of_property_read_u32(node, "num-interpolated-steps", &num_steps);
if (!ret && num_steps) {
Whoops! I was playing around with the 80-char limit and forgot to
revert. The lines should read:
ret = of_property_read_u32(node, "num-interpolated-steps",
&num_steps);
if (!ret && num_steps) {
I haven't checked the underling code, but is it even feasible for
of_property_read_u32() to not succeed AND for num_steps to be set?
If not, the check for !ret if superfluous and you can drop it.
quoted
+ /*
+ * Make sure that there is at least two entries in the
s/is/are/
quoted
+ * brightness-levels table, otherwise we can't
+ * interpolate
Why break the line here?
quoted
+ * 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
From: Daniel Thompson <hidden> Date: 2018-07-18 08:26:30
On Wed, Jul 18, 2018 at 09:09:13AM +0100, Lee Jones wrote:
On Mon, 16 Jul 2018, Daniel Thompson wrote:
quoted
Currently, if the DT does not define num-interpolated-steps then
num_steps is undefined and the interpolation code will deploy randomly.
Fix this.
Fixes: 573fe6d1c25c ("backlight: pwm_bl: Linear interpolation between
brightness-levels")
Reported-by: Marcel Ziswiler <redacted>
Signed-off-by: Daniel Thompson <redacted>
Signed-off-by: Marcel Ziswiler <redacted>
This line is confusing. Did you guys author this patch together?
Yes (although the manipulations were fairly mechanical).
My guess is that this line should be dropped and the RB and TB tags
should remain? If it was reviewed too, perhaps an AB too?
@@ -299,15 +299,14 @@ static int pwm_backlight_parse_dt(struct device *dev,*interpolationbetweeneachofthevaluesofbrightnesslevels*andcreatesanewpre-computedtable.*/-of_property_read_u32(node,"num-interpolated-steps",-&num_steps);--/*-*Makesurethatthereisatleasttwoentriesinthe-*brightness-levelstable,otherwisewecan'tinterpolate-*betweentwopoints.-*/-if(num_steps){+if((of_property_read_u32(node,"num-interpolated-steps",+&num_steps)=0)&&num_steps){
This is pretty ugly, and isn't it suffering from over-bracketing? My
suggestion would be to break out the invocation of
of_property_read_u32() from the if and test only the result.
of_property_read_u32(node, "num-interpolated-steps", &num_steps);
if (!ret && num_steps) {
I haven't checked the underling code, but is it even feasible for
of_property_read_u32() to not succeed AND for num_steps to be set?
If not, the check for !ret if superfluous and you can drop it.
quoted
+ /*
+ * Make sure that there is at least two entries in the
s/is/are/
quoted
+ * brightness-levels table, otherwise we can't
+ * interpolate
Why break the line here?
quoted
+ * 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
From: Lee Jones <hidden> Date: 2018-07-18 09:53:44
On Wed, 18 Jul 2018, Marcel Ziswiler wrote:
On Wed, 2018-07-18 at 09:09 +0100, Lee Jones wrote:
quoted
On Mon, 16 Jul 2018, Daniel Thompson wrote:
quoted
Currently, if the DT does not define num-interpolated-steps then
num_steps is undefined and the interpolation code will deploy
randomly.
Fix this.
Fixes: 573fe6d1c25c ("backlight: pwm_bl: Linear interpolation
between
brightness-levels")
Reported-by: Marcel Ziswiler <redacted>
Signed-off-by: Daniel Thompson <redacted>
Signed-off-by: Marcel Ziswiler <redacted>
This line is confusing. Did you guys author this patch together?
Yes, I reported it and we came to a conclusion together.
It sounds like you need to have all of the tags (except this one). :)
Reported-by: for reporting the issue
Suggested-by: for suggesting a resolution
Acked-by: for reviewing it
Tested-by: for testing it
Signed-off-by usually means you either wrote a significant amount of
the diffstat or you were part of the submission path.
quoted
My guess is that this line should be dropped and the RB and TB tags
should remain? If it was reviewed too, perhaps an AB too?
I'm OK either way and do not need any explicit authorship to be
expressed for me.
In this instance I suggest keeping Reported-by and Tested-by.
@@ -299,15 +299,14 @@ static int pwm_backlight_parse_dt(struct
device *dev,
* 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) {
+ if ((of_property_read_u32(node, "num-interpolated-
steps",
+ &num_steps) = 0) &&
num_steps) {
This is pretty ugly, and isn't it suffering from over-bracketing? My
suggestion would be to break out the invocation of
of_property_read_u32() from the if and test only the result.
of_property_read_u32(node, "num-interpolated-steps",
&num_steps);
you mean:
ret = of_property_read_u32(node, "num-interpolated-
steps", &num_steps);
quoted
if (!ret && num_steps) {
I haven't checked the underling code, but is it even feasible for
of_property_read_u32() to not succeed AND for num_steps to be set?
If not, the check for !ret if superfluous and you can drop it.
No, then we are back to the initial issue of num_steps potentially not
being initialised. We really want both of_property_read_u32() to
succeed AND num_steps to actually be set.
I also think num_steps should be pre-initialised.
Then it will only be set if of_property_read_u32() succeeds.
--
Lee Jones [李琼斯]
Linaro Services Technical Lead
Linaro.org │ Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog
From: Daniel Thompson <hidden> Date: 2018-07-18 10:12:35
On Wed, Jul 18, 2018 at 10:53:35AM +0100, Lee Jones wrote:
On Wed, 18 Jul 2018, Marcel Ziswiler wrote:
quoted
On Wed, 2018-07-18 at 09:09 +0100, Lee Jones wrote:
quoted
On Mon, 16 Jul 2018, Daniel Thompson wrote:
quoted
Currently, if the DT does not define num-interpolated-steps then
num_steps is undefined and the interpolation code will deploy
randomly.
Fix this.
Fixes: 573fe6d1c25c ("backlight: pwm_bl: Linear interpolation
between
brightness-levels")
Reported-by: Marcel Ziswiler <redacted>
Signed-off-by: Daniel Thompson <redacted>
Signed-off-by: Marcel Ziswiler <redacted>
This line is confusing. Did you guys author this patch together?
Yes, I reported it and we came to a conclusion together.
It sounds like you need to have all of the tags (except this one). :)
Reported-by: for reporting the issue
Suggested-by: for suggesting a resolution
Acked-by: for reviewing it
Tested-by: for testing it
Signed-off-by usually means you either wrote a significant amount of
the diffstat or you were part of the submission path.
He did [I don't object to but wouldn't have used the extra brackets you
brought up ;-) ].
quoted
quoted
My guess is that this line should be dropped and the RB and TB tags
should remain? If it was reviewed too, perhaps an AB too?
I'm OK either way and do not need any explicit authorship to be
expressed for me.
In this instance I suggest keeping Reported-by and Tested-by.
@@ -299,15 +299,14 @@ static int pwm_backlight_parse_dt(struct
device *dev,
* 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) {
+ if ((of_property_read_u32(node, "num-interpolated-
steps",
+ &num_steps) = 0) &&
num_steps) {
This is pretty ugly, and isn't it suffering from over-bracketing? My
suggestion would be to break out the invocation of
of_property_read_u32() from the if and test only the result.
of_property_read_u32(node, "num-interpolated-steps",
&num_steps);
you mean:
ret = of_property_read_u32(node, "num-interpolated-
steps", &num_steps);
quoted
if (!ret && num_steps) {
I haven't checked the underling code, but is it even feasible for
of_property_read_u32() to not succeed AND for num_steps to be set?
If not, the check for !ret if superfluous and you can drop it.
No, then we are back to the initial issue of num_steps potentially not
being initialised. We really want both of_property_read_u32() to
succeed AND num_steps to actually be set.
I also think num_steps should be pre-initialised.
Then it will only be set if of_property_read_u32() succeeds.
--
Lee Jones [李琼斯]
Linaro Services Technical Lead
Linaro.org │ Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog
From: Lee Jones <hidden> Date: 2018-07-18 13:09:01
On Wed, 18 Jul 2018, Marcel Ziswiler wrote:
On Wed, 2018-07-18 at 11:12 +0100, Daniel Thompson wrote:
quoted
On Wed, Jul 18, 2018 at 10:53:35AM +0100, Lee Jones wrote:
quoted
On Wed, 18 Jul 2018, Marcel Ziswiler wrote:
quoted
On Wed, 2018-07-18 at 09:09 +0100, Lee Jones wrote:
quoted
On Mon, 16 Jul 2018, Daniel Thompson wrote:
quoted
Currently, if the DT does not define num-interpolated-steps
then
num_steps is undefined and the interpolation code will deploy
randomly.
Fix this.
Fixes: 573fe6d1c25c ("backlight: pwm_bl: Linear interpolation
between
brightness-levels")
Reported-by: Marcel Ziswiler <redacted>
Signed-off-by: Daniel Thompson <redacted>
Signed-off-by: Marcel Ziswiler <redacted>
This line is confusing. Did you guys author this patch
together?
Yes, I reported it and we came to a conclusion together.
It sounds like you need to have all of the tags (except this one).
:)
Reported-by: for reporting the issue
Suggested-by: for suggesting a resolution
Acked-by: for reviewing it
Tested-by: for testing it
Signed-off-by usually means you either wrote a significant amount
of
the diffstat or you were part of the submission path.
He did [I don't object to but wouldn't have used the extra brackets
you
brought up ;-) ].
Yes, I take all the blame for the extra brackets. Regardless of having
a masters in CS or not I still prefer too many then too few of them (;-
p).
quoted
quoted
quoted
quoted
My guess is that this line should be dropped and the RB and TB
tags
should remain? If it was reviewed too, perhaps an AB too?
I'm OK either way and do not need any explicit authorship to be
expressed for me.
In this instance I suggest keeping Reported-by and Tested-by.
pwm_backlight_parse_dt(struct
device *dev,
* 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) {
+ if ((of_property_read_u32(node, "num-
interpolated-
steps",
+ &num_steps) = 0)
&&
num_steps) {
This is pretty ugly, and isn't it suffering from over-
bracketing? My
suggestion would be to break out the invocation of
of_property_read_u32() from the if and test only the result.
of_property_read_u32(node, "num-interpolated-
steps",
&num_steps);
you mean:
ret = of_property_read_u32(node, "num-interpolated-
steps", &num_steps);
quoted
if (!ret && num_steps) {
I haven't checked the underling code, but is it even feasible
for
of_property_read_u32() to not succeed AND for num_steps to be
set?
If not, the check for !ret if superfluous and you can drop it.
No, then we are back to the initial issue of num_steps
potentially not
being initialised. We really want both of_property_read_u32() to
succeed AND num_steps to actually be set.
I also think num_steps should be pre-initialised.
Yes, I guess it definitely does not hurt.
quoted
quoted
Then it will only be set if of_property_read_u32() succeeds.
Yes, but we still need to check for both, the function not failing and
num_steps to actually be non zero.
Why? You don't do anything differently if it fails.
--
Lee Jones [李琼斯]
Linaro Services Technical Lead
Linaro.org │ Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog
From: Daniel Thompson <hidden> Date: 2018-07-18 13:41:11
On Wed, Jul 18, 2018 at 02:08:53PM +0100, Lee Jones wrote:
quoted
quoted
quoted
quoted
No, then we are back to the initial issue of num_steps
potentially not
being initialised. We really want both of_property_read_u32() to
succeed AND num_steps to actually be set.
I also think num_steps should be pre-initialised.
Yes, I guess it definitely does not hurt.
quoted
quoted
Then it will only be set if of_property_read_u32() succeeds.
Yes, but we still need to check for both, the function not failing and
num_steps to actually be non zero.
Why? You don't do anything differently if it fails.
Only if you initialize num_steps...
We should either initialize to zero and not worry about the return
code[1] or we check the return code and not worry about
initialization[2]. I don't think both are worthwhile.
Whilst initialization can fix this specific instance we generally avoid
overusing it since it messes up static analysis and, in this instance,
distance from declaration to use is >25 lines, hence current patchset.
Daniel.
[1] https://lkml.org/lkml/2018/7/16/399
[2] https://lkml.org/lkml/2018/7/16/1042
Or...
We check the return code and leave number
num_steps is uninitialized and stack allocated so it only has a valid
value if of_property_read_u32() succeeds.
We can (and I originally did) fix the bug by initializing num_steps to 0
but its quite some distance between declaration and use so I accepted
Marcel's counter proposal to check the return code instead.
Daniel.
From: Lee Jones <hidden> Date: 2018-07-18 15:55:51
On Wed, 18 Jul 2018, Daniel Thompson wrote:
On Wed, Jul 18, 2018 at 02:08:53PM +0100, Lee Jones wrote:
quoted
quoted
quoted
quoted
quoted
No, then we are back to the initial issue of num_steps
potentially not
being initialised. We really want both of_property_read_u32() to
succeed AND num_steps to actually be set.
I also think num_steps should be pre-initialised.
Yes, I guess it definitely does not hurt.
quoted
quoted
Then it will only be set if of_property_read_u32() succeeds.
Yes, but we still need to check for both, the function not failing and
num_steps to actually be non zero.
Why? You don't do anything differently if it fails.
Only if you initialize num_steps...
We should either initialize to zero and not worry about the return
code[1] or we check the return code and not worry about
initialization[2]. I don't think both are worthwhile.
Whilst initialization can fix this specific instance we generally avoid
overusing it since it messes up static analysis and, in this instance,
distance from declaration to use is >25 lines, hence current patchset.
Daniel.
[1] https://lkml.org/lkml/2018/7/16/399
[2] https://lkml.org/lkml/2018/7/16/1042
Or...
We check the return code and leave number
num_steps is uninitialized and stack allocated so it only has a valid
value if of_property_read_u32() succeeds.
We can (and I originally did) fix the bug by initializing num_steps to 0
but its quite some distance between declaration and use so I accepted
Marcel's counter proposal to check the return code instead.
Only checking the return value of of_property_read_u32() is also
suitable.
--
Lee Jones [李琼斯]
Linaro Services Technical Lead
Linaro.org │ Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog
From: Daniel Thompson <hidden> Date: 2018-07-18 16:34:13
On Wed, Jul 18, 2018 at 04:55:44PM +0100, Lee Jones wrote:
On Wed, 18 Jul 2018, Daniel Thompson wrote:
quoted
On Wed, Jul 18, 2018 at 02:08:53PM +0100, Lee Jones wrote:
quoted
quoted
quoted
quoted
quoted
No, then we are back to the initial issue of num_steps
potentially not
being initialised. We really want both of_property_read_u32() to
succeed AND num_steps to actually be set.
I also think num_steps should be pre-initialised.
Yes, I guess it definitely does not hurt.
quoted
quoted
Then it will only be set if of_property_read_u32() succeeds.
Yes, but we still need to check for both, the function not failing and
num_steps to actually be non zero.
Why? You don't do anything differently if it fails.
Only if you initialize num_steps...
We should either initialize to zero and not worry about the return
code[1] or we check the return code and not worry about
initialization[2]. I don't think both are worthwhile.
Whilst initialization can fix this specific instance we generally avoid
overusing it since it messes up static analysis and, in this instance,
distance from declaration to use is >25 lines, hence current patchset.
Daniel.
[1] https://lkml.org/lkml/2018/7/16/399
[2] https://lkml.org/lkml/2018/7/16/1042
Or...
We check the return code and leave number
num_steps is uninitialized and stack allocated so it only has a valid
value if of_property_read_u32() succeeds.
We can (and I originally did) fix the bug by initializing num_steps to 0
but its quite some distance between declaration and use so I accepted
Marcel's counter proposal to check the return code instead.
Only checking the return value of of_property_read_u32() is also
suitable.
I did think about that case... I concluded that it isn't wrong for a
DT to set to this property to 0 (effectively meaning "no interpolated
steps please").
If we take the branch when num_steps is zero we get a bunch of pointless
housekeeping that amounts to no more than an extremely elaborate
malloc/memcpy/free.
Daniel.
From: Daniel Thompson <hidden> Date: 2018-07-19 16:19:47
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(-)
From: Lee Jones <hidden> Date: 2018-07-23 07:23:50
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 ... ;)
@@ -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)returnret;ret=of_property_read_u32(node,"default-brightness-level",&value);-if(ret<0)+if(!ret)returnret;
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
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From: Lee Jones <hidden> Date: 2018-07-23 07:25:41
On Wed, 18 Jul 2018, Daniel Thompson wrote:
On Wed, Jul 18, 2018 at 04:55:44PM +0100, Lee Jones wrote:
quoted
On Wed, 18 Jul 2018, Daniel Thompson wrote:
quoted
On Wed, Jul 18, 2018 at 02:08:53PM +0100, Lee Jones wrote:
quoted
quoted
quoted
quoted
quoted
No, then we are back to the initial issue of num_steps
potentially not
being initialised. We really want both of_property_read_u32() to
succeed AND num_steps to actually be set.
I also think num_steps should be pre-initialised.
Yes, I guess it definitely does not hurt.
quoted
quoted
Then it will only be set if of_property_read_u32() succeeds.
Yes, but we still need to check for both, the function not failing and
num_steps to actually be non zero.
Why? You don't do anything differently if it fails.
Only if you initialize num_steps...
We should either initialize to zero and not worry about the return
code[1] or we check the return code and not worry about
initialization[2]. I don't think both are worthwhile.
Whilst initialization can fix this specific instance we generally avoid
overusing it since it messes up static analysis and, in this instance,
distance from declaration to use is >25 lines, hence current patchset.
Daniel.
[1] https://lkml.org/lkml/2018/7/16/399
[2] https://lkml.org/lkml/2018/7/16/1042
Or...
We check the return code and leave number
num_steps is uninitialized and stack allocated so it only has a valid
value if of_property_read_u32() succeeds.
We can (and I originally did) fix the bug by initializing num_steps to 0
but its quite some distance between declaration and use so I accepted
Marcel's counter proposal to check the return code instead.
Only checking the return value of of_property_read_u32() is also
suitable.
I did think about that case... I concluded that it isn't wrong for a
DT to set to this property to 0 (effectively meaning "no interpolated
steps please").
If we take the branch when num_steps is zero we get a bunch of pointless
housekeeping that amounts to no more than an extremely elaborate
malloc/memcpy/free.
Yet in the latest patch, you do it anyway? Or have I misread it?
--
Lee Jones [李琼斯]
Linaro Services Technical Lead
Linaro.org │ Open source software for ARM SoCs
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From: Daniel Thompson <hidden> Date: 2018-07-24 06:48:52
On Mon, Jul 23, 2018 at 08:23:43AM +0100, Lee Jones wrote:
On Thu, 19 Jul 2018, Daniel Thompson wrote:
quoted
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 ... ;)
@@ -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)returnret;ret=of_property_read_u32(node,"default-brightness-level",&value);-if(ret<0)+if(!ret)returnret;
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.
quoted
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?
No, it's bogus. Looks like when I broke the if statement into two
clauses I ended up flipping the && to an ||.
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) {
quoted
+ /*
+ * 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
From: Daniel Thompson <hidden> Date: 2018-07-24 07:01:21
On Mon, Jul 23, 2018 at 08:23:43AM +0100, Lee Jones wrote:
On Thu, 19 Jul 2018, Daniel Thompson wrote:
quoted
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 ... ;)
@@ -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)returnret;ret=of_property_read_u32(node,"default-brightness-level",&value);-if(ret<0)+if(!ret)returnret;
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.
Did wonder which way to go on this... I figured this close I'd accept
code either way so adopted fewest patches.
However I will split this out because I'm going to go back to the orignal
pre-v1 approach of just initializing the damn variable.
quoted
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) {
quoted
+ /*
+ * 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
From: Daniel Thompson <hidden> Date: 2018-07-24 07:12:46
Currently, if the DT does not define num-interpolated-steps then
num_steps is undefined and the interpolation code will deploy randomly.
Fix with a simple initialize to zero.
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:
v3:
- Switch to the simplest fix and zero the uninitialized variable. git
grep indicates that ~25% of calls to of_property_read_u32() use this
pattern (pre-initialize optional properties with sane values and
ignore the return code).
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 | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
From: Doug Anderson <dianders@chromium.org> Date: 2018-07-24 23:56:13
Hi,
On Tue, Jul 24, 2018 at 12:12 AM, Daniel Thompson
[off-list ref] wrote:
Currently, if the DT does not define num-interpolated-steps then
num_steps is undefined and the interpolation code will deploy randomly.
Fix with a simple initialize to zero.
Fixes: 573fe6d1c25c ("backlight: pwm_bl: Linear interpolation between
brightness-levels")
I think it may be incorrect to word-wrap the Fixes line. A quick grep
through the source code looks like others agree.
Reported-by: Marcel Ziswiler <redacted>
Signed-off-by: Daniel Thompson <redacted>
Tested-by: Marcel Ziswiler <redacted>
---
Notes:
v3:
- Switch to the simplest fix and zero the uninitialized variable. git
grep indicates that ~25% of calls to of_property_read_u32() use this
pattern (pre-initialize optional properties with sane values and
ignore the return code).
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 | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
Other than the nit on the commit message, this simple fix seems sane.
Reviewed-by: Douglas Anderson <dianders@chromium.org>
From: Lee Jones <hidden> Date: 2018-07-25 05:22:18
On Tue, 24 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 with a simple initialize to zero.
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:
v3:
- Switch to the simplest fix and zero the uninitialized variable. git
grep indicates that ~25% of calls to of_property_read_u32() use this
pattern (pre-initialize optional properties with sane values and
ignore the return code).
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 | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
Once the 'Fixes:' line has been repaired:
Acked-by: Lee Jones [off-list ref]
--
Lee Jones [李琼斯]
Linaro Services Technical Lead
Linaro.org │ Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog
From: Daniel Thompson <hidden> Date: 2018-07-25 07:38:42
Currently, if the DT does not define num-interpolated-steps then
num_steps is undefined and the interpolation code will deploy randomly.
Fix with a simple initialize to zero.
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>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Acked-by: Lee Jones <redacted>
---
Notes:
v4:
- Remove line break from Fixes: and update the *-by:s
v3:
- Switch to the simplest fix and zero the uninitialized variable. git
grep indicates that ~25% of calls to of_property_read_u32() use this
pattern (pre-initialize optional properties with sane values and
ignore the return code).
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 | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
From: Lee Jones <hidden> Date: 2018-07-25 08:04:03
On Wed, 25 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 with a simple initialize to zero.
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>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Acked-by: Lee Jones <redacted>
---
Notes:
v4:
- Remove line break from Fixes: and update the *-by:s
v3:
- Switch to the simplest fix and zero the uninitialized variable. git
grep indicates that ~25% of calls to of_property_read_u32() use this
pattern (pre-initialize optional properties with sane values and
ignore the return code).
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 | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
Applied, thanks.
--
Lee Jones [李琼斯]
Linaro Services Technical Lead
Linaro.org │ Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog