Hi Sakari, On 2017-07-20 19:14:01 +0300, Sakari Ailus wrote: > Hi Hans, > > Thanks for the review. > > On Wed, Jul 19, 2017 at 01:42:55PM +0200, Hans Verkuil wrote: > > On 18/07/17 21:03, Sakari Ailus wrote: > > > Hi folks, > > > > > > This RFC patchset achieves a number of things which I've put to the same > > > patchset for they need to be show together to demonstrate the use cases. > > > > > > I don't really intend this to compete with Niklas's patchset but much of > > > the problem area addressed by the two is the same. > > > > > > Comments would be welcome. > > > > > > - Add AS3645A LED flash class driver. > > > > > > - Add async notifiers (by Niklas). > > > > > > - V4L2 sub-device node registration is moved to take place at the same time > > > with the registration of the sub-device itself. With this change, > > > sub-device node registration behaviour is aligned with video node > > > registration. > > > > > > - The former is made possible by moving the bound() callback after > > > sub-device registration. > > > > > > - As all the device node registration and link creation is done as the > > > respective devices are probed, there is no longer dependency to the > > > notifier complete callback which as itself is seen problematic. The > > > complete callback still exists but there's no need to use it, pending > > > changes in individual drivers. > > > > > > See: > > > <URL:http://www.spinics.net/lists/linux-media/msg118323.html> > > > > > > As a result, if a part of the media device fails to initialise because it > > > is e.g. physically broken, it will be possible to use what works. > > > > I've got major problems with this from a userspace point of view. In the vast > > majority of cases you just want to bail out if one or more subdevs fail. > > I admit it's easier for the user space if the device becomes available only > when all its component drivers have registered. > > Also remember that video nodes are registered in the file system right on > device probe time. It's only sub-device and media device node registration > that has taken place in the notifier's complete handler. Is this always the case? In the R-Car VIN driver I register the video devices using video_register_device() in the complete handler. Am I doing things wrong in that driver? I had a patch where I moved the video_register_device() call to probe time but it got shoot down in review and was dropped. > > There are things how we could do this easier, for instance providing events > on the media device on entity registration and possibly registration state > (whether all entities have been registered). > > This way the user space can easily choose whether it would like to proceed > using a partially functional device (or not). > > -- > Sakari Ailus > e-mail: sakari.ailus@xxxxxx XMPP: sailus@xxxxxxxxxxxxxx -- Regards, Niklas Söderlund
