linux-kernel - Re: [PATCH 1/2] drivers: fwnode: fix fwnode_irq_get

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Date:   Tue, 25 Oct 2022 12:17:27 +0300
From:   Matti Vaittinen <mazziesaccount@...il.com>
To:     Sakari Ailus <sakari.ailus@...ux.intel.com>
Cc:     Matti Vaittinen <matti.vaittinen@...rohmeurope.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Daniel Scally <djrscally@...il.com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Wolfram Sang <wsa@...nel.org>,
        Akhil R <akhilrajeev@...dia.com>, linux-acpi@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-i2c@...r.kernel.org
Subject: Re: [PATCH 1/2] drivers: fwnode: fix 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@...ux.intel.com>
>> Signed-off-by: Matti Vaittinen <mazziesaccount@...il.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@...ux.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

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

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