Re: [PATCH v5 18/35] v4l: Allow changing control handler lock

[Sylwester Nawrocki <s.nawrocki@samsung.com>]

On 05/14/2012 05:27 PM, Sylwester Nawrocki wrote:
> Hi Sakari,
> 
> On 03/06/2012 05:32 PM, Sakari Ailus wrote:
>> Allow choosing the lock used by the control handler. This may be handy
>> sometimes when a driver providing multiple subdevs does not want to use
>> several locks to serialise its functions.
>>
>> Signed-off-by: Sakari Ailus <sakari.ailus@iki.fi>
>> ---
>>  drivers/media/video/adp1653.c    |    8 +++---
>>  drivers/media/video/v4l2-ctrls.c |   39 +++++++++++++++++++------------------
>>  drivers/media/video/vivi.c       |    4 +-
>>  include/media/v4l2-ctrls.h       |    9 +++++--
>>  4 files changed, 32 insertions(+), 28 deletions(-)
> ...
>> diff --git a/include/media/v4l2-ctrls.h b/include/media/v4l2-ctrls.h
>> index 533315b..71abac0 100644
>> --- a/include/media/v4l2-ctrls.h
>> +++ b/include/media/v4l2-ctrls.h
>> @@ -168,7 +168,9 @@ struct v4l2_ctrl_ref {
>>  /** struct v4l2_ctrl_handler - The control handler keeps track of all the
>>    * controls: both the controls owned by the handler and those inherited
>>    * from other handlers.
>> +  * @_lock:	Default for "lock".
>>    * @lock:	Lock to control access to this handler and its controls.
>> +  *		May be replaced by the user right after init.
>>    * @ctrls:	The list of controls owned by this handler.
>>    * @ctrl_refs:	The list of control references.
>>    * @cached:	The last found control reference. It is common that the same
>> @@ -179,7 +181,8 @@ struct v4l2_ctrl_ref {
>>    * @error:	The error code of the first failed control addition.
>>    */
>>  struct v4l2_ctrl_handler {
>> -	struct mutex lock;
>> +	struct mutex _lock;
>> +	struct mutex *lock;
> 
> I think we have an issue here. All drivers that reference ctrl_handler.lock
> directly need to be updated, since the 'lock' member of struct v4l2_ctrl_handler
> is now a pointer. So instead 
> 
> mutex_lock(&ctrl_handler.lock);
> 
> they should now do
> 
> mutex_lock(ctrl_handler.lock);
> 
> Or am I missing something ?
> 
> For example, I'm getting following error:
> 
> drivers/media/video/s5p-fimc/fimc-core.c: In function ‘fimc_ctrls_activate’:
> drivers/media/video/s5p-fimc/fimc-core.c:678: warning: passing argument 1 of ‘mutex_lock’ from incompatible pointer type
> include/linux/mutex.h:152: note: expected ‘struct mutex *’ but argument is of type ‘struct mutex **’
> drivers/media/video/s5p-fimc/fimc-core.c:697: warning: passing argument 1 of ‘mutex_unlock’ from incompatible pointer type
> include/linux/mutex.h:169: note: expected ‘struct mutex *’ but argument is of type ‘struct mutex **’
> 
> AFAICT only vivi and s5p-fimc drivers use the control handler lock 
> directly, so I can prepare a patch updating those drivers.

OK, vivi and adp1653 are already modified in this patch, so s5p-fimc
seems the only one left. I'll fix that.

Regards,
Sylwester