On Mon, 9 Mar 2009 08:16:53 +0100 Hans Verkuil <hverkuil@xxxxxxxxx> wrote: > On Monday 09 March 2009 02:07:33 Trent Piepho wrote: > > On Sun, 8 Mar 2009, Hans Verkuil wrote: > > > The last one fixes an ivtv regression caused by this change: > > > > > > changeset: 10811:0a0eba8e64d5 > > > user: Trent Piepho <xyzzy@xxxxxxxxxxxxx> > > > date: Tue Mar 03 20:21:02 2009 -0800 > > > summary: videodev: only copy needed part of RW ioctl's parameter > > > > > > The fix is simple: switch on the full ioctl command instead of just the > > > NR field. > > > > > > Thanks to Martin Dauskardt for doing the bisect and tracing the > > > breakage to this change. > > > > Switching on the whole ioctl makes the switch statement a lot less > > efficient. I'd rather just put a if (_IOC_TYPE(cmd) != 'V') return 0; in > > there. That should fix the non-v4l2 ioctls, right? > > That was my first thought as well, but I realized that this is one area > where you really do not want to take any risk. IMO, it is better to use Trent's way, and reduce the number of places that do memset(0). > Personally I think this code is overoptimization. In my view the performance > advantage is minimal while reducing the readability of the code. In general, it is a good idea to avoid copying a data that won't be used from userspace. I liked the optimizations done. Let's just fix what's broken and test a lot to avoid causing a kernel regression. Cheers, Mauro -- 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
