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    SubjectRe: [PATCH] Store the relevant miscdevice in file->private_data in misc_open()
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    On Thu, 2008-11-13 at 16:18 -0800, Greg KH wrote:
    > On Fri, Nov 14, 2008 at 10:54:41AM +1100, Michael Ellerman wrote:
    > > On Thu, 2008-11-13 at 09:31 -0800, Greg KH wrote:
    > > > On Thu, Nov 13, 2008 at 03:49:50PM +1100, Michael Ellerman wrote:
    > > > > Currently it's not easy to share file_operations between multiple
    > > > > instances of a miscdevice. In order to do this, the device code needs to
    > > > > store a list of all it's miscdevice instances, and when fops->open() is
    > > > > called, search the list and find the right device based on the minor
    > > > > number.
    > > > >
    > > > > However the generic miscdevice code already has a list of miscdevices,
    > > > > and uses this to find the right device in misc_open(). If misc_open()
    > > > > would store the miscdevice it found in file->private_data, then the
    > > > > device code wouldn't need to worry about storing it's own separate list
    > > > > and searching that as well.
    > > > >
    > > > > The rest of the miscdevice code does not use file->private_data, so the
    > > > > device code is still free to use file->private_data for something else
    > > > > if it wants to.
    > > > >
    > > > > Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
    > > >
    > > > Do you have a follow-on patch for some misc device using code that would
    > > > take advantage of this change?
    > >
    > > Ah, good point. I do, but not for upstream :/
    >
    > Hm, then I have to ask why should we take this change?

    Because it's seems like a good idea.

    If that's your only objection I'll find some in-tree drivers that can
    use it, drivers/char/tpm/tpm.c looks like it could use it for starters.
    It's a bit hard to tell but there might be some others.

    > And why would the driver not be availble for upstream to take?

    Because it's a hacky pile of crud, and it's for unreleased and
    non-existent hardware.

    cheers

    --
    Michael Ellerman
    OzLabs, IBM Australia Development Lab

    wwweb: http://michael.ellerman.id.au
    phone: +61 2 6212 1183 (tie line 70 21183)

    We do not inherit the earth from our ancestors,
    we borrow it from our children. - S.M.A.R.T Person
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