[1/2] drivers: fwnode: fix fwnode_irq_get_byname()

  The fwnode_irq_get_byname() does return 0 upon device-tree IRQ mapping
failure. This is contradicting the function documentation and can
potentially be a source of errors like:

int probe(...) {
	...

	irq = fwnode_irq_get_byname();
	if (irq <= 0)
		return irq;

	...
}

Here we do correctly check the return value from fwnode_irq_get_byname()
but the driver probe will now return success. (There was already one
such user in-tree).

Change the fwnode_irq_get_byname() to work as documented and according to
the common convention and abd always return a negative errno upon failure.

Fixes: ca0acb511c21 ("device property: Add fwnode_irq_get_byname")
Suggested-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com>

---

I did a quick audit for the callers at v6.1-rc2:
drivers/i2c/i2c-smbus.c
drivers/iio/accel/adxl355_core.c
drivers/iio/gyro/fxas21002c_core.c
drivers/iio/imu/adis16480.c
drivers/iio/imu/bmi160/bmi160_core.c
drivers/iio/imu/bmi160/bmi160_core.c

I did not spot any errors to be caused by this change. There will be a
functional change in i2c-smbus.c as the probe will now return -EINVAL
should the IRQ dt-mapping fail. It'd be nice if this was checked to be
Ok by the peeps knowing the i2c-smbus :)
---
 drivers/base/property.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)
  

Moi,

On Tue, Oct 25, 2022 at 11:50:59AM +0300, Matti Vaittinen wrote:
> The fwnode_irq_get_byname() does return 0 upon device-tree IRQ mapping
> failure. This is contradicting the function documentation and can
> potentially be a source of errors like:
> 
> int probe(...) {
> 	...
> 
> 	irq = fwnode_irq_get_byname();
> 	if (irq <= 0)
> 		return irq;
> 
> 	...
> }
> 
> Here we do correctly check the return value from fwnode_irq_get_byname()
> but the driver probe will now return success. (There was already one
> such user in-tree).
> 
> Change the fwnode_irq_get_byname() to work as documented and according to
> the common convention and abd always return a negative errno upon failure.
> 
> Fixes: ca0acb511c21 ("device property: Add fwnode_irq_get_byname")
> Suggested-by: Sakari Ailus <sakari.ailus@linux.intel.com>
> Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com>
> 
> ---
> 
> I did a quick audit for the callers at v6.1-rc2:
> drivers/i2c/i2c-smbus.c
> drivers/iio/accel/adxl355_core.c
> drivers/iio/gyro/fxas21002c_core.c
> drivers/iio/imu/adis16480.c
> drivers/iio/imu/bmi160/bmi160_core.c
> drivers/iio/imu/bmi160/bmi160_core.c
> 
> I did not spot any errors to be caused by this change. There will be a

It won't as you're decreasing the possible values the function may
return...

> functional change in i2c-smbus.c as the probe will now return -EINVAL
> should the IRQ dt-mapping fail. It'd be nice if this was checked to be
> Ok by the peeps knowing the i2c-smbus :)

FWIW, for both patches (but see below):

Reviewed-by: Sakari Ailus <sakari.ailus@linux.intel.com>

> ---
>  drivers/base/property.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/base/property.c b/drivers/base/property.c
> index 4d6278a84868..bfc6c7286db2 100644
> --- a/drivers/base/property.c
> +++ b/drivers/base/property.c
> @@ -964,7 +964,7 @@ EXPORT_SYMBOL(fwnode_irq_get);
>   */
>  int fwnode_irq_get_byname(const struct fwnode_handle *fwnode, const char *name)
>  {
> -	int index;
> +	int index, ret;
>  
>  	if (!name)
>  		return -EINVAL;
> @@ -973,7 +973,12 @@ int fwnode_irq_get_byname(const struct fwnode_handle *fwnode, const char *name)
>  	if (index < 0)
>  		return index;
>  
> -	return fwnode_irq_get(fwnode, index);
> +	ret = fwnode_irq_get(fwnode, index);
> +

This newline is extra.

Or:

	return ret ?: -EINVAL;

Or even:

	return fwnode_irq_get(fwnode, index) ?: -EINVAL;

Up to you.

> +	if (!ret)
> +		return -EINVAL;
> +
> +	return ret;
>  }
>  EXPORT_SYMBOL(fwnode_irq_get_byname);
  

Moro Sakari,

Thanks for the review (and the suggestion)!

On 10/25/22 12:08, Sakari Ailus wrote:
> Moi,
> 
> On Tue, Oct 25, 2022 at 11:50:59AM +0300, Matti Vaittinen wrote:
>> The fwnode_irq_get_byname() does return 0 upon device-tree IRQ mapping
>> failure. This is contradicting the function documentation and can
>> potentially be a source of errors like:
>>
>> int probe(...) {
>> 	...
>>
>> 	irq = fwnode_irq_get_byname();
>> 	if (irq <= 0)
>> 		return irq;
>>
>> 	...
>> }
>>
>> Here we do correctly check the return value from fwnode_irq_get_byname()
>> but the driver probe will now return success. (There was already one
>> such user in-tree).
>>
>> Change the fwnode_irq_get_byname() to work as documented and according to
>> the common convention and abd always return a negative errno upon failure.
>>
>> Fixes: ca0acb511c21 ("device property: Add fwnode_irq_get_byname")
>> Suggested-by: Sakari Ailus <sakari.ailus@linux.intel.com>
>> Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com>
>>
>> ---
>>
>> I did a quick audit for the callers at v6.1-rc2:
>> drivers/i2c/i2c-smbus.c
>> drivers/iio/accel/adxl355_core.c
>> drivers/iio/gyro/fxas21002c_core.c
>> drivers/iio/imu/adis16480.c
>> drivers/iio/imu/bmi160/bmi160_core.c
>> drivers/iio/imu/bmi160/bmi160_core.c
>>
>> I did not spot any errors to be caused by this change. There will be a
> 
> It won't as you're decreasing the possible values the function may
> return...
> 

Unless someone had implemented special handling for the IRQ mapping 
failure...

>> functional change in i2c-smbus.c as the probe will now return -EINVAL
>> should the IRQ dt-mapping fail. It'd be nice if this was checked to be
>> Ok by the peeps knowing the i2c-smbus :)
> 
> FWIW, for both patches (but see below):
> 
> Reviewed-by: Sakari Ailus <sakari.ailus@linux.intel.com>
> 
>> ---
>>   drivers/base/property.c | 9 +++++++--
>>   1 file changed, 7 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/base/property.c b/drivers/base/property.c
>> index 4d6278a84868..bfc6c7286db2 100644
>> --- a/drivers/base/property.c
>> +++ b/drivers/base/property.c
>> @@ -964,7 +964,7 @@ EXPORT_SYMBOL(fwnode_irq_get);
>>    */
>>   int fwnode_irq_get_byname(const struct fwnode_handle *fwnode, const char *name)
>>   {
>> -	int index;
>> +	int index, ret;
>>   
>>   	if (!name)
>>   		return -EINVAL;
>> @@ -973,7 +973,12 @@ int fwnode_irq_get_byname(const struct fwnode_handle *fwnode, const char *name)
>>   	if (index < 0)
>>   		return index;
>>   
>> -	return fwnode_irq_get(fwnode, index);
>> +	ret = fwnode_irq_get(fwnode, index);
>> +
> 
> This newline is extra.
> 
> Or:
> 
> 	return ret ?: -EINVAL;
> 
> Or even:
> 
> 	return fwnode_irq_get(fwnode, index) ?: -EINVAL;
> 
> Up to you.
> 

My personal preference is to not use the ternary. I think the plain 
clarity of if() just in many places justifies burning couple of lines 
more :)

Yours
	-- Matti
  

On Tue, Oct 25, 2022 at 11:50:59AM +0300, Matti Vaittinen wrote:
> The fwnode_irq_get_byname() does return 0 upon device-tree IRQ mapping
> failure. This is contradicting the function documentation and can
> potentially be a source of errors like:
> 
> int probe(...) {
> 	...
> 
> 	irq = fwnode_irq_get_byname();
> 	if (irq <= 0)
> 		return irq;
> 
> 	...
> }
> 
> Here we do correctly check the return value from fwnode_irq_get_byname()
> but the driver probe will now return success. (There was already one
> such user in-tree).
> 
> Change the fwnode_irq_get_byname() to work as documented and according to
> the common convention and abd always return a negative errno upon failure.

...

> +	ret = fwnode_irq_get(fwnode, index);

> +

Redundant blank line and better to use traditional pattern:

> +	if (!ret)
> +		return -EINVAL;
> +
> +	return ret;

	if (ret)
		return ret;

	/* We treat mapping errors as invalid case */
	return -EINVAL;

>  }
  

Hi Andy,

Thanks for the review.

On 10/25/22 12:18, Andy Shevchenko wrote:
> On Tue, Oct 25, 2022 at 11:50:59AM +0300, Matti Vaittinen wrote:
>> The fwnode_irq_get_byname() does return 0 upon device-tree IRQ mapping
>> failure. This is contradicting the function documentation and can
>> potentially be a source of errors like:
>>
>> int probe(...) {
>> 	...
>>
>> 	irq = fwnode_irq_get_byname();
>> 	if (irq <= 0)
>> 		return irq;
>>
>> 	...
>> }
>>
>> Here we do correctly check the return value from fwnode_irq_get_byname()
>> but the driver probe will now return success. (There was already one
>> such user in-tree).
>>
>> Change the fwnode_irq_get_byname() to work as documented and according to
>> the common convention and abd always return a negative errno upon failure.
> 
> ...
> 
>> +	ret = fwnode_irq_get(fwnode, index);
> 
>> +
> 
> Redundant blank line and better to use traditional pattern: >
>> +	if (!ret)
>> +		return -EINVAL;
>> +
>> +	return ret;
> 
> 	if (ret)
> 		return ret;
> 
> 	/* We treat mapping errors as invalid case */
> 	return -EINVAL;
> 
>>   }

I like the added comment - but in this case I don't prefer the 
"traditional pattern" you suggest. We do check for a very special error 
case indicated by ret 0.

if (!ret)
	return -EINVAL;

makes it obvious the zero is special error.

if (ret)
	return ret;

the traditional pattern makes this look like traditional error return - 
which it is not. The comment you added is nice though. It could be just 
before the check for

if (!ret).

I can cook v2 later when I have finished my current task - which may or 
may not take a while though....

Yours
	-- Matti
-- 
Matti Vaittinen
Linux kernel developer at ROHM Semiconductors
Oulu Finland

~~ When things go utterly wrong vim users can always type :help! ~~
  

On Tue, Oct 25, 2022 at 10:00:07AM +0000, Vaittinen, Matti wrote:
> On 10/25/22 12:18, Andy Shevchenko wrote:
> > On Tue, Oct 25, 2022 at 11:50:59AM +0300, Matti Vaittinen wrote:

...

> >> +	ret = fwnode_irq_get(fwnode, index);
> > 
> >> +
> > 
> > Redundant blank line and better to use traditional pattern: >
> >> +	if (!ret)
> >> +		return -EINVAL;
> >> +
> >> +	return ret;
> > 
> > 	if (ret)
> > 		return ret;
> > 
> > 	/* We treat mapping errors as invalid case */
> > 	return -EINVAL;
> > 
> >>   }
> 
> I like the added comment - but in this case I don't prefer the 
> "traditional pattern" you suggest. We do check for a very special error 
> case indicated by ret 0.
> 
> if (!ret)
> 	return -EINVAL;
> 
> makes it obvious the zero is special error.

I don't think so. It makes ! easily to went through the cracks. If you want an
explicit, use ' == 0' and add a comment.

> if (ret)
> 	return ret;
> 
> the traditional pattern makes this look like traditional error return - 
> which it is not. The comment you added is nice though. It could be just 
> before the check for
> 
> if (!ret).