linux-kernel - Re: [PATCH] Store the relevant miscdevice in file->private_data in misc

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Message-ID: <491CF82B.7040703@oracle.com>
Date:	Thu, 13 Nov 2008 20:01:47 -0800
From:	Randy Dunlap <randy.dunlap@...cle.com>
To:	Greg KH <greg@...ah.com>
CC:	Michael Ellerman <michael@...erman.id.au>,
	linux-kernel@...r.kernel.org, Andrew Morton <akpm@...l.org>,
	viro@...iv.linux.org.uk
Subject: Re: [PATCH] Store the relevant miscdevice in file->private_data in
 misc_open()

Greg KH wrote:
> On Fri, Nov 14, 2008 at 01:50:52PM +1100, Michael Ellerman wrote:
>> 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@...erman.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.
> 
> You know we don't make changes to core code for drivers that aren't in
> the main tree, this is not a new thing...
> 
>>> 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.
> 
> That's what the drivers/staging/ tree is for, send it on over to me and
> I'll add it to that location.

for non-existent hardware??  that's not a good plan.


-- 
~Randy
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