Hi Mauro, On Sunday 04 September 2011 00:21:38 Mauro Carvalho Chehab wrote: > Em 24-08-2011 10:25, Laurent Pinchart escreveu: > > On Wednesday 24 August 2011 14:19:01 Hiremath, Vaibhav wrote: > >> On Wednesday, August 24, 2011 5:00 PM Laurent Pinchart wrote: > >>> On Wednesday 24 August 2011 13:21:27 Ravi, Deepthy wrote: > >>>> On Wed, Aug 24, 2011 at 4:47 PM, Laurent Pinchart wrote: > >>>>> On Friday 19 August 2011 15:48:45 Deepthy Ravi wrote: > >>>>>> From: Vaibhav Hiremath <hvaibhav@xxxxxx> > >>>>>> > >>>>>> Fix the build break caused when CONFIG_MEDIA_CONTROLLER > >>>>>> option is disabled and if any sensor driver has to be used > >>>>>> between MC and non MC framework compatible devices. > >>>>>> > >>>>>> For example,if tvp514x video decoder driver migrated to > >>>>>> MC framework is being built without CONFIG_MEDIA_CONTROLLER > >>>>>> option enabled, the following error messages will result. > >>>>>> drivers/built-in.o: In function `tvp514x_remove': > >>>>>> drivers/media/video/tvp514x.c:1285: undefined reference to > >>>>>> `media_entity_cleanup' > >>>>>> drivers/built-in.o: In function `tvp514x_probe': > >>>>>> drivers/media/video/tvp514x.c:1237: undefined reference to > >>>>>> `media_entity_init' > >>>>> > >>>>> If the tvp514x is migrated to the MC framework, its Kconfig option > >>>>> should depend on MEDIA_CONTROLLER. > >>>> > >>>> The same TVP514x driver is being used for both MC and non MC > >>>> compatible devices, for example OMAP3 and AM35x. So if it is made > >>>> dependent on MEDIA CONTROLLER, we cannot enable the driver for MC > >>>> independent devices. > >>> > >>> Then you should use conditional compilation in the tvp514x driver > >>> itself. Or > >> > >> No. I am not in favor of conditional compilation in driver code. > > > > Actually, thinking some more about this, you should make the tvp514x > > driver depend on CONFIG_MEDIA_CONTROLLER unconditionally. This doesn't > > mean that the driver will become unusable by applications that are not > > MC-aware. Hosts/bridges don't have to export subdev nodes, they can just > > call subdev pad-level operations internally and let applications control > > the whole device through a single V4L2 video node. > > > >>> better, port the AM35x driver to the MC API. > >> > >> Why should we use MC if I have very simple device (like AM35x) which > >> only supports single path? I can very well use simple V4L2 sub-dev > >> based approach (master - slave), isn't it? > > > > The AM35x driver should use the in-kernel MC and V4L2 subdev APIs, but it > > doesn't have to expose them to userspace. > > I don't agree. If AM35x doesn't expose the MC API to userspace, > CONFIG_MEDIA_CONTROLLER should not be required at all. > > Also, according with the Linux best practices, when #if tests for config > symbols are required, developers should put it into the header files, and > not inside the code, as it helps to improve code readability. From > Documentation/SubmittingPatches: > > 2) #ifdefs are ugly > > Code cluttered with ifdefs is difficult to read and maintain. Don't do > it. Instead, put your ifdefs in a header, and conditionally define > 'static inline' functions, or macros, which are used in the code. > Let the compiler optimize away the "no-op" case. > > So, this patch is perfectly fine on my eyes. I'm sorry, but I don't agree. Regarding the V4L2 subdev pad-level API, the goal is to convert all host and subdev drivers to it, so that's definitely the way to go. This does *not* mean that subdevs must expose a subdev device node. That's entirely optional. What I'm talking about is switching from video::*_mbus_fmt operations to pad::*_fmt operations. The pad-level format operations are very similar to video-level format operations, and more generic. Drivers shouldn't implement both. Regarding the MC API, drivers are not required to register a media_device instance. I have no issue with that. However, drivers should initialized the subdev's embedded media_entity, as that's required by subdev pad-level operations to get the number of pads for a subdev. This will result in no modification to the userspace. -- Regards, Laurent Pinchart -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
