Messages in this thread | | | Date | Wed, 8 Oct 2014 06:43:07 -0700 | From | Greg KH <> | Subject | Re: [PATCH] misc: always assign miscdevice to file->private_data in open() |
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On Wed, Oct 08, 2014 at 10:47:54AM +0200, Martin Kepplinger wrote: > As of now, a miscdevice driver has to provide an implementation of > the open() file operation if it wants to have misc_open() assign a > pointer to struct miscdevice to file->private_data for other file > operations to use (given the user calls open()). > > This leads to situations where a miscdevice driver that doesn't need > internal operations during open() has to implement open() that only > returns immediately, in order to use the data in private_data in other > fops.
Yeah, that's messy, do we have any in-kernel misc drivers that do this?
> This change provides consistent behaviour for miscdevice developers by > always providing the pointer in private_data. A driver's open() fop would, > of course, just overwrite it, when using private_data itself. > > Signed-off-by: Martin Kepplinger <martink@posteo.de> > --- > This is really only a question: Do I understand this correctly, and, > could this change then hurt any existing driver?
I don't know, take a look at the existing ones and see please.
> As a driver developer it took me a while to figure out what happens here, > and in my situation it would have been nice to just have this feature as > part of the miscdevice API. Possibly documented somewhere?
Patches always accepted for documentation :)
> misc_open() is called in any case, on open(). As long as miscdevice drivers > don't explicitly rely on private_data being NULL exactly IF they don't > implement an open() fop (which I wouldn't imagine), this would make things > even more convenient.
I agree, but it would be great if you can audit the existing misc drivers to ensure we don't break anything with this change. Can you do that please?
thanks,
greg k-h
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