Hi Hans, On Thursday 29 April 2010 08:44:29 Hans Verkuil wrote: > On Thursday 29 April 2010 05:42:39 Frederic Weisbecker wrote: > > Hi, > > > > Linus suggested to rename struct v4l2_file_operations::ioctl > > into bkl_ioctl to eventually get something greppable and make > > its background explicit. > > > > While at it I thought it could be a good idea to just pushdown > > the bkl to every v4l drivers that have an .ioctl, so that we > > actually remove struct v4l2_file_operations::ioctl for good. > > > > It passed make allyesconfig on sparc. > > Please tell me what you think. > > I much prefer to keep the bkl inside the v4l2 core. One reason is that I > think that we can replace the bkl in the core with a mutex. Still not > ideal of course, so the next step will be to implement proper locking in > each driver. For this some additional v4l infrastructure work needs to be > done. I couldn't proceed with that until the v4l events API patches went > in, and that happened yesterday. > > So from my point of view the timeline is this: > > 1) I do the infrastructure work this weekend. This will make it much easier > to convert drivers to do proper locking. And it will also simplify > v4l2_priority handling, so I'm killing two birds with one stone :-) > > 2) Wait until Arnd's patch gets merged that pushes the bkl down to > v4l2-dev.c > > 3) Investigate what needs to be done to replace the bkl with a v4l2-dev.c > global mutex. Those drivers that call the bkl themselves should probably be > converted to do proper locking, but there are only about 14 drivers that do > this. The other 60 or so drivers should work fine if a v4l2-dev global lock > is used. At this point the bkl is effectively removed from the v4l > subsystem. > > 4) Work on the remaining 60 drivers to do proper locking and get rid of the > v4l2-dev global lock. This is probably less work than it sounds. > > Since your patch moves everything down to the driver level it will actually > make this work harder rather than easier. And it touches almost all drivers > as well.
Every driver will need to be carefully checked to make sure the BKL can be replaced by a v4l2-dev global mutex. Why would it be more difficult to do so if the BKL is pushed down to the drivers ? -- Regards, Laurent Pinchart -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html