Re: [PATCH] Store the relevant miscdevice in file->private_data in misc_open()

[Michael Ellerman <michael@ellerman.id.au>]

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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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