On Friday, June 24, 2011 15:45:59 Devin Heitmueller wrote: > On Fri, Jun 24, 2011 at 9:29 AM, Mauro Carvalho Chehab > <mchehab@xxxxxxxxxxxxx> wrote: > >> MythTV has a bunch of these too (mainly so the code can adapt to > >> driver bugs that are fixed in later revisions). Putting Mauro's patch > >> upstream will definitely cause breakage. > > > > It shouldn't, as ivtv driver version is lower than 3.0.0. All the old bug fixes > > aren't needed if version is >= 3.0.0. > > > > Besides that, trusting on a driver revision number to detect that a bug is > > there is not the right thing to do, as version numbers are never increased at > > the stable kernels (nor distro modified kernels take care of increasing revision > > number as patches are backported there). > > The versions are increased at the discretion of the driver maintainer, > usually when there is some userland visible change in driver behavior. > I assure you the application developers don't *want* to rely on such > a mechanism, but there have definitely been cases in the past where > there was no easy way to detect the behavior of the driver from > userland. > > It lets application developers work around things like violations of > the V4L2 standard which get fixed in newer revisions of the driver. > It provides them the ability to put a hack in their code that says "if > (version < X) then this driver feature is broken and I shouldn't use > it." Indeed. Ideally we shouldn't need it. But reality is different. What we have right now works and I see no compelling reason to change the behavior. Regards, Hans > > In other words, relying on it doesn't work fine. > > It's the best (and really only solution) we have today. > > >> Also, it screws up the ability for users to get fixes through the > >> media_build tree (unless you are increasing the revision constantly > >> with every merge you do). > > > > Why? Developers don't increase version numbers on every applied patch > > (with is great, as it avoids merge conflicts). > > The driver maintainer doesn't *have* to increase the version - he does > it when he thinks it's appropriate. The point is you are taking that > discretion out of *their* hands, and you yourself are unaware of when > it is actually needed. > > You need to stop looking at this from a purist standpoint and think of > how application developers actually use the API. They need tools like > this to allow them to work around driver bugs while having a source > codebase which operates against different kernels (including kernels > that may still have those bugs). > > Sure, in a perfect world where drivers don't have bugs and > applications don't have to run against older kernels, what you are > saying is not illogical. But then again, we don't live in a perfect > world. > > Devin > > -- 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
