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| Started by | Shuah Khan <shuahkh@osg.samsung.com> |
|---|---|
| First post | 2015-12-12 00:40 +0100 |
| Last post | 2015-12-21 13:20 +0100 |
| Articles | 3 — 3 participants |
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Re: [PATCH v5 1/3] [media] media-device: check before unregister if mdev was registered Shuah Khan <shuahkh@osg.samsung.com> - 2015-12-12 00:40 +0100
Re: [PATCH v5 1/3] [media] media-device: check before unregister if mdev was registered Mauro Carvalho Chehab <mchehab@osg.samsung.com> - 2015-12-15 11:50 +0100
Re: [PATCH v5 1/3] [media] media-device: check before unregister if mdev was registered Javier Martinez Canillas <javier@osg.samsung.com> - 2015-12-21 13:20 +0100
| From | Shuah Khan <shuahkh@osg.samsung.com> |
|---|---|
| Date | 2015-12-12 00:40 +0100 |
| Subject | Re: [PATCH v5 1/3] [media] media-device: check before unregister if mdev was registered |
| Message-ID | <qEFs5-2HI-1@gated-at.bofh.it> |
On 12/11/2015 03:57 PM, Javier Martinez Canillas wrote:
> Most media functions that unregister, check if the corresponding register
> function succeed before. So these functions can safely be called even if a
> registration was never made or the component as already been unregistered.
>
> Add the same check to media_device_unregister() function for consistency.
>
> This will also allow to split the media_device_register() function in an
> initialization and registration functions without the need to change the
> generic cleanup functions and error code paths for all the media drivers.
>
> Suggested-by: Sakari Ailus <sakari.ailus@linux.intel.com>
> Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
> Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
>
> ---
>
> Changes in v5: None
> Changes in v4: None
> Changes in v3: None
> Changes in v2:
> - Reword the documentation for media_device_unregister(). Suggested by Sakari.
> - Added Sakari's Acked-by tag for patch #1.
>
> drivers/media/media-device.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/drivers/media/media-device.c b/drivers/media/media-device.c
> index c12481c753a0..11c1c7383361 100644
> --- a/drivers/media/media-device.c
> +++ b/drivers/media/media-device.c
> @@ -577,6 +577,8 @@ EXPORT_SYMBOL_GPL(__media_device_register);
> * media_device_unregister - unregister a media device
> * @mdev: The media device
> *
> + * It is safe to call this function on an unregistered
> + * (but initialised) media device.
> */
> void media_device_unregister(struct media_device *mdev)
> {
> @@ -584,6 +586,10 @@ void media_device_unregister(struct media_device *mdev)
> struct media_entity *next;
> struct media_interface *intf, *tmp_intf;
>
> + /* Check if mdev was ever registered at all */
> + if (!media_devnode_is_registered(&mdev->devnode))
> + return;
This is a good check, however, this check will not prevent
media_device_unregister() from getting run twice by two
different drivers. i.e media_devnode gets unregistered
towards the end of at the end of media_device_unregister().
In an example case, if bridge driver and snd-usb-aduio both
call media_device_unregister(), this check won't help prevent
media_device_unregister() being done only once. I think we
need a different state variable in struct media_device
to ensure unregister is done only once.
> +
> /* Remove all entities from the media device */
> list_for_each_entry_safe(entity, next, &mdev->entities, graph_obj.list)
> media_device_unregister_entity(entity);
>
--
Shuah Khan
Sr. Linux Kernel Developer
Open Source Innovation Group
Samsung Research America (Silicon Valley)
shuahkh@osg.samsung.com | (970) 217-8978
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| From | Mauro Carvalho Chehab <mchehab@osg.samsung.com> |
|---|---|
| Date | 2015-12-15 11:50 +0100 |
| Message-ID | <qFVl8-2T6-7@gated-at.bofh.it> |
| In reply to | #1290013 |
Em Fri, 11 Dec 2015 16:36:27 -0700
Shuah Khan <shuahkh@osg.samsung.com> escreveu:
> On 12/11/2015 03:57 PM, Javier Martinez Canillas wrote:
> > Most media functions that unregister, check if the corresponding register
> > function succeed before. So these functions can safely be called even if a
> > registration was never made or the component as already been unregistered.
> >
> > Add the same check to media_device_unregister() function for consistency.
> >
> > This will also allow to split the media_device_register() function in an
> > initialization and registration functions without the need to change the
> > generic cleanup functions and error code paths for all the media drivers.
> >
> > Suggested-by: Sakari Ailus <sakari.ailus@linux.intel.com>
> > Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
> > Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
> >
> > ---
> >
> > Changes in v5: None
> > Changes in v4: None
> > Changes in v3: None
> > Changes in v2:
> > - Reword the documentation for media_device_unregister(). Suggested by Sakari.
> > - Added Sakari's Acked-by tag for patch #1.
> >
> > drivers/media/media-device.c | 6 ++++++
> > 1 file changed, 6 insertions(+)
> >
> > diff --git a/drivers/media/media-device.c b/drivers/media/media-device.c
> > index c12481c753a0..11c1c7383361 100644
> > --- a/drivers/media/media-device.c
> > +++ b/drivers/media/media-device.c
> > @@ -577,6 +577,8 @@ EXPORT_SYMBOL_GPL(__media_device_register);
> > * media_device_unregister - unregister a media device
> > * @mdev: The media device
> > *
> > + * It is safe to call this function on an unregistered
> > + * (but initialised) media device.
> > */
> > void media_device_unregister(struct media_device *mdev)
> > {
> > @@ -584,6 +586,10 @@ void media_device_unregister(struct media_device *mdev)
> > struct media_entity *next;
> > struct media_interface *intf, *tmp_intf;
> >
> > + /* Check if mdev was ever registered at all */
> > + if (!media_devnode_is_registered(&mdev->devnode))
> > + return;
>
> This is a good check, however, this check will not prevent
> media_device_unregister() from getting run twice by two
> different drivers. i.e media_devnode gets unregistered
> towards the end of at the end of media_device_unregister().
>
> In an example case, if bridge driver and snd-usb-aduio both
> call media_device_unregister(), this check won't help prevent
> media_device_unregister() being done only once. I think we
> need a different state variable in struct media_device
> to ensure unregister is done only once.
True. We need move the spin_lock() code to be called before
calling media_device_is_registered().
I'm sending such patches.
Thanks for reporting it.
Regards,
Mauro
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| From | Javier Martinez Canillas <javier@osg.samsung.com> |
|---|---|
| Date | 2015-12-21 13:20 +0100 |
| Message-ID | <qI7Bw-6nS-15@gated-at.bofh.it> |
| In reply to | #1292035 |
Hello Mauro,
On 12/15/2015 07:41 AM, Mauro Carvalho Chehab wrote:
> Em Fri, 11 Dec 2015 16:36:27 -0700
> Shuah Khan <shuahkh@osg.samsung.com> escreveu:
>
>> On 12/11/2015 03:57 PM, Javier Martinez Canillas wrote:
>>> Most media functions that unregister, check if the corresponding register
>>> function succeed before. So these functions can safely be called even if a
>>> registration was never made or the component as already been unregistered.
>>>
>>> Add the same check to media_device_unregister() function for consistency.
>>>
>>> This will also allow to split the media_device_register() function in an
>>> initialization and registration functions without the need to change the
>>> generic cleanup functions and error code paths for all the media drivers.
>>>
>>> Suggested-by: Sakari Ailus <sakari.ailus@linux.intel.com>
>>> Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
>>> Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
>>>
>>> ---
>>>
>>> Changes in v5: None
>>> Changes in v4: None
>>> Changes in v3: None
>>> Changes in v2:
>>> - Reword the documentation for media_device_unregister(). Suggested by Sakari.
>>> - Added Sakari's Acked-by tag for patch #1.
>>>
>>> drivers/media/media-device.c | 6 ++++++
>>> 1 file changed, 6 insertions(+)
>>>
>>> diff --git a/drivers/media/media-device.c b/drivers/media/media-device.c
>>> index c12481c753a0..11c1c7383361 100644
>>> --- a/drivers/media/media-device.c
>>> +++ b/drivers/media/media-device.c
>>> @@ -577,6 +577,8 @@ EXPORT_SYMBOL_GPL(__media_device_register);
>>> * media_device_unregister - unregister a media device
>>> * @mdev: The media device
>>> *
>>> + * It is safe to call this function on an unregistered
>>> + * (but initialised) media device.
>>> */
>>> void media_device_unregister(struct media_device *mdev)
>>> {
>>> @@ -584,6 +586,10 @@ void media_device_unregister(struct media_device *mdev)
>>> struct media_entity *next;
>>> struct media_interface *intf, *tmp_intf;
>>>
>>> + /* Check if mdev was ever registered at all */
>>> + if (!media_devnode_is_registered(&mdev->devnode))
>>> + return;
>>
>> This is a good check, however, this check will not prevent
>> media_device_unregister() from getting run twice by two
>> different drivers. i.e media_devnode gets unregistered
>> towards the end of at the end of media_device_unregister().
>>
>> In an example case, if bridge driver and snd-usb-aduio both
>> call media_device_unregister(), this check won't help prevent
>> media_device_unregister() being done only once. I think we
>> need a different state variable in struct media_device
>> to ensure unregister is done only once.
>
> True. We need move the spin_lock() code to be called before
> calling media_device_is_registered().
>
I see, the check in $SUBJECT was to avoid each driver to have a similar
check for cleanup in its error path but I didn't take into account the
fact that two drivers may share the same struct media_device, as you
explained to me is the case for ALSA and V4L2 MC integration.
> I'm sending such patches.
>
Thanks, I'll review and test them.
> Thanks for reporting it.
>
> Regards,
> Mauro
>
Best regards,
--
Javier Martinez Canillas
Open Source Group
Samsung Research America
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