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Re: [PATCH] iio: gyro: ssp_gyro_sensor: Use devm_iio_device_register

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  Re: [PATCH] iio: gyro: ssp_gyro_sensor: Use devm_iio_device_register Vaishali Thakkar <vthakkar1994@gmail.com> - 2015-09-27 06:20 +0200
    Re: [PATCH] iio: gyro: ssp_gyro_sensor: Use devm_iio_device_register Jonathan Cameron <jic23@kernel.org> - 2015-09-27 15:40 +0200
      Re: [PATCH] iio: gyro: ssp_gyro_sensor: Use devm_iio_device_register Vaishali Thakkar <vthakkar1994@gmail.com> - 2015-09-28 03:20 +0200
        Re: [PATCH] iio: gyro: ssp_gyro_sensor: Use devm_iio_device_register Vaishali Thakkar <vthakkar1994@gmail.com> - 2015-09-28 12:10 +0200
          Re: [PATCH] iio: gyro: ssp_gyro_sensor: Use devm_iio_device_register Karol Wrona <k.wrona@samsung.com> - 2015-09-29 12:30 +0200

#1233610 — Re: [PATCH] iio: gyro: ssp_gyro_sensor: Use devm_iio_device_register

On Mon, Sep 21, 2015 at 4:48 PM, Karol Wrona <k.wrona@samsung.com> wrote:
> On 09/21/2015 11:53 AM, Jonathan Cameron wrote:
>>
>>
>> On 21 September 2015 09:18:39 BST, Karol Wrona <k.wrona@samsung.com> 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@gmail.com>
>>>> 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.

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.

>>>
>>> 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);
>>>>>
>>>>
>>>> --
>>>> To unsubscribe from this list: send the line "unsubscribe linux-iio"
>>> in
>>>> the body of a message to majordomo@vger.kernel.org
>>>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>>>
>>
>



-- 
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#1233664

On 27/09/15 05:16, Vaishali Thakkar wrote:
> On Mon, Sep 21, 2015 at 4:48 PM, Karol Wrona <k.wrona@samsung.com> wrote:
>> On 09/21/2015 11:53 AM, Jonathan Cameron wrote:
>>>
>>>
>>> On 21 September 2015 09:18:39 BST, Karol Wrona <k.wrona@samsung.com> 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@gmail.com>
>>>>> 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);
>>>>>>
>>>>>
>>>>> --
>>>>> To unsubscribe from this list: send the line "unsubscribe linux-iio"
>>>> in
>>>>> the body of a message to majordomo@vger.kernel.org
>>>>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>>>>
>>>
>>
> 
> 
> 

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#1233809

On Sun, Sep 27, 2015 at 7:01 PM, Jonathan Cameron <jic23@kernel.org> wrote:
> On 27/09/15 05:16, Vaishali Thakkar wrote:
>> On Mon, Sep 21, 2015 at 4:48 PM, Karol Wrona <k.wrona@samsung.com> wrote:
>>> On 09/21/2015 11:53 AM, Jonathan Cameron wrote:
>>>>
>>>>
>>>> On 21 September 2015 09:18:39 BST, Karol Wrona <k.wrona@samsung.com> 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@gmail.com>
>>>>>> 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.

Ok. Then I'll send patches for both of these files.

>>>>>
>>>>> 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);
>>>>>>>
>>>>>>
>>>>>> --
>>>>>> To unsubscribe from this list: send the line "unsubscribe linux-iio"
>>>>> in
>>>>>> the body of a message to majordomo@vger.kernel.org
>>>>>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>>>>>
>>>>
>>>
>>
>>
>>
>



-- 
Vaishali
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#1234002

On Mon, Sep 28, 2015 at 6:42 AM, Vaishali Thakkar
<vthakkar1994@gmail.com> wrote:
> On Sun, Sep 27, 2015 at 7:01 PM, Jonathan Cameron <jic23@kernel.org> wrote:
>> On 27/09/15 05:16, Vaishali Thakkar wrote:
>>> On Mon, Sep 21, 2015 at 4:48 PM, Karol Wrona <k.wrona@samsung.com> wrote:
>>>> On 09/21/2015 11:53 AM, Jonathan Cameron wrote:
>>>>>
>>>>>
>>>>> On 21 September 2015 09:18:39 BST, Karol Wrona <k.wrona@samsung.com> 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@gmail.com>
>>>>>>> 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.
>
> Ok. Then I'll send patches for both of these files.

Sorry, probably I was not clear enough in my last mail. I mean I'll
send patches patches
once we will have something like 'ssp_deregister_consumer'. But is
there anyone who
is working on this? Is it possible to introduce devm counterpart of the same?
How much will it be useful [taking note that there are only 3-4 files
which are using it]?

>>>>>>
>>>>>> 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);
>>>>>>>>
>>>>>>>
>>>>>>> --
>>>>>>> To unsubscribe from this list: send the line "unsubscribe linux-iio"
>>>>>> in
>>>>>>> the body of a message to majordomo@vger.kernel.org
>>>>>>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>>>>>>
>>>>>
>>>>
>>>
>>>
>>>
>>
>
>
>
> --
> Vaishali



-- 
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#1234946

On 09/28/2015 12:08 PM, Vaishali Thakkar wrote:
> On Mon, Sep 28, 2015 at 6:42 AM, Vaishali Thakkar
> <vthakkar1994@gmail.com> wrote:
>> On Sun, Sep 27, 2015 at 7:01 PM, Jonathan Cameron <jic23@kernel.org> wrote:
>>> On 27/09/15 05:16, Vaishali Thakkar wrote:
>>>> On Mon, Sep 21, 2015 at 4:48 PM, Karol Wrona <k.wrona@samsung.com> wrote:
>>>>> On 09/21/2015 11:53 AM, Jonathan Cameron wrote:
>>>>>>
>>>>>>
>>>>>> On 21 September 2015 09:18:39 BST, Karol Wrona <k.wrona@samsung.com> 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@gmail.com>
>>>>>>>> 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.
>>
>> Ok. Then I'll send patches for both of these files.
> 
> Sorry, probably I was not clear enough in my last mail. I mean I'll
> send patches patches
> once we will have something like 'ssp_deregister_consumer'. But is
> there anyone who
> is working on this? Is it possible to introduce devm counterpart of the same?

If you want you can simply add ssp_deregister_consumer (to ssp_dev.c)
function and use it in the remove (in ssp sensor platform driver). I
will test it.

We can use devm_iio_device_register for iio dev itself but better check
what is called first - driver remove callback or the devm removes.
If we deregister internally the iio device from ssp we should be quite safe.


> How much will it be useful [taking note that there are only 3-4 files
> which are using it]?
> 
>>>>>>>
>>>>>>> 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);
>>>>>>>>>
>>>>>>>>
>>>>>>>> --
>>>>>>>> To unsubscribe from this list: send the line "unsubscribe linux-iio"
>>>>>>> in
>>>>>>>> the body of a message to majordomo@vger.kernel.org
>>>>>>>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>>>>>>>
>>>>>>
>>>>>
>>>>
>>>>
>>>>
>>>
>>
>>
>>
>> --
>> Vaishali
> 
> 
> 

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