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    SubjectRe: [RFC/PATCH] sysfs'ify video4linux
    On Thu, Jul 17, 2003 at 02:49:07PM -0700, Greg KH wrote:
    > On Thu, Jul 17, 2003 at 06:37:15PM +0200, Gerd Knorr wrote:
    > >
    > > Version (1) can be done without breaking the build, with a hack along
    > > the lines "if (no release callback) printk(KERN_WARN please fix your
    > > driver)", so the drivers can be fixed step-by-step afterwards.
    > That sounds like a nice way to start.
    > > Fixing the drivers might be non-trivial through. Some drivers are
    > > hot-pluggable (usb cams), some drivers register more than one v4l device
    > > (bttv wants up to three). Those drivers can't just call kfree() in the
    > > ->release callback because there might be other references, some open
    > > file handle for a unplugged usb cam, another not-yet unregistered
    > > v4l device, whatever. Probably they must implement some reference
    > > counting scheme to get that right. The very simple ones (in
    > > drivers/media/radio for example) likely just need the kfree() moved
    > > from the ->remove function into the new ->release() callback.
    > I don't think it will be that bad for them. Just have them change the
    > v4l device from being a structure included in their structure, into a
    > pointer, and then create it before registering, and free it in the
    > release() callback.
    > That being said, I haven't actually looked at the code to verify that
    > this is all that is needed :)
    > > Version (2) needs every v4l driver touched to make it compile again.
    > > Not sure how hard it is to fixup them. I'd guess it is pretty straigt
    > > forward to do the conversion, it's just alot of work. I also could do
    > > a number of other cleanups along the way. Maybe I trap into some hidden
    > > pitfalls through, havn't looked at all the drivers in detail yet.
    > Breaking the build is a very good thing to do at times, to ensure that
    > stuff gets fixed properly. Users might go for a while without realizing
    > that there really is a problem in their driver.
    > But in the end, it's up to you...
    > thanks,
    > greg k-h

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