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    SubjectRe: [RFC/PATCH] sysfs'ify video4linux
    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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