On 27/09/15 05:16, Vaishali Thakkar wrote:
> On Mon, Sep 21, 2015 at 4:48 PM, Karol Wrona <k.wrona@xxxxxxxxxxx> wrote:
>> On 09/21/2015 11:53 AM, Jonathan Cameron wrote:
>>>
>>>
>>> On 21 September 2015 09:18:39 BST, Karol Wrona <k.wrona@xxxxxxxxxxx> wrote:
>>>> On 09/20/2015 09:18 PM, Jonathan Cameron wrote:
>>>>> On 14/09/15 17:08, Vaishali Thakkar wrote:
>>>>>> Use resourced managed function devm_iio_device_register to
>>>>>> make error path simpler. To be compatible with the change,
>>>>>> the remove function is removed as it is now redundant.
>>>>>>
>>>>>> Signed-off-by: Vaishali Thakkar <vthakkar1994@xxxxxxxxx>
>>>>> This patch is reasonable, but makes me wonder if there is an issue
>>>>> in the remove path for this driver. It relies on the ssp_sensors
>>>> common
>>>>> module. That in ssp_spi.c uses the fact ssp_register_consumer
>>>>> has saved the struct iio_dev into a local array in the core driver.
>>>>> I think this means that a remove of this function will leave a
>>>> possible
>>>>> null pointer de reference.
>>>> You are right. In this case we need something like
>>>> ssp_deregister_consumer(...) in ssp_dev.c. So I think that "remove
>>>> func"
>>>> should stay. Of course we can switch to devm iio register.
>>> Not if you want to remove the userspace interface before doing you new function call. Doing so gives a nasty race.
>> So better leave it out:
>> iio_device_unregister(indio_dev) will disable the buffers and through
>> ops disables the sensor and than remove iio dev ptr from the internal table.
>>
>
> Sorry for the late reply. Yes, I guess I missed the point that
> 'ssp_register_consumer' is
> used in probe function. And I believe that devm_iio_register is useful
> only when we
> can convert all other functions to their devm counterparts and remove
> function will go
> away.
Yes. Exactly.
>
> But then why don't we need ssp_deregister_consumer here in the remove function?
> Is it automatically handled by iio_device_unregister? I guess Karol
> tried to explain
> the same thing but I am still confused. Same case applies for
> ssp_sensors/ssp_dev.c.
We do indeed need an ssp_deregister_consumer function to be called in the remove.
I don't think one currently exists, so that needs fixing.
>
>>>>
>>>> Also the same can (rather should) be done for accelerometer sensor
>>>> (ssp_accel_sensor.c).
>>>>
>>>> Vaishali, if you want please feel free and send patch.
>>>>
>>>>>
>>>>> Now I suspect that case doesn't actually occur because the relevant
>>>>> device elements are disabled whenever this module is removed. Having
>>>>> said that we might expect an ssp_unregister_consumer function that
>>>>> sets the relevant pointer back to null on removal so as to avoid
>>>>> any possible race conditions around driver removal / reprobing.
>>>>> A spot of defensive programming rather than necessarily a bug to be
>>>>> fixed!
>>>>>
>>>>> One little process thing. This driver was written by Karol so patches
>>>>> should probably always cc Karol as well as the more general
>>>>> maintainer / reviewers for IIO. Added cc.
>>>>>
>>>>> Jonathan
>>>>>> ---
>>>>>> drivers/iio/gyro/ssp_gyro_sensor.c | 12 +-----------
>>>>>> 1 file changed, 1 insertion(+), 11 deletions(-)
>>>>>>
>>>>>> diff --git a/drivers/iio/gyro/ssp_gyro_sensor.c
>>>> b/drivers/iio/gyro/ssp_gyro_sensor.c
>>>>>> index 0a8afdd..ac88de7 100644
>>>>>> --- a/drivers/iio/gyro/ssp_gyro_sensor.c
>>>>>> +++ b/drivers/iio/gyro/ssp_gyro_sensor.c
>>>>>> @@ -134,7 +134,7 @@ static int ssp_gyro_probe(struct platform_device
>>>> *pdev)
>>>>>>
>>>>>> platform_set_drvdata(pdev, indio_dev);
>>>>>>
>>>>>> - ret = iio_device_register(indio_dev);
>>>>>> + ret = devm_iio_device_register(&pdev->dev, indio_dev);
>>>>>> if (ret < 0)
>>>>>> return ret;
>>>>>>
>>>>>> @@ -144,21 +144,11 @@ static int ssp_gyro_probe(struct
>>>> platform_device *pdev)
>>>>>> return 0;
>>>>>> }
>>>>>>
>>>>>> -static int ssp_gyro_remove(struct platform_device *pdev)
>>>>>> -{
>>>>>> - struct iio_dev *indio_dev = platform_get_drvdata(pdev);
>>>>>> -
>>>>>> - iio_device_unregister(indio_dev);
>>>>>> -
>>>>>> - return 0;
>>>>>> -}
>>>>>> -
>>>>>> static struct platform_driver ssp_gyro_driver = {
>>>>>> .driver = {
>>>>>> .name = SSP_GYROSCOPE_NAME,
>>>>>> },
>>>>>> .probe = ssp_gyro_probe,
>>>>>> - .remove = ssp_gyro_remove,
>>>>>> };
>>>>>>
>>>>>> module_platform_driver(ssp_gyro_driver);
>>>>>>
>>>>>
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>>>
>>
>
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