linux-kernel - Re: [PATCH v2] misc: Reserve minor for VFIO

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Date:	Wed, 18 Dec 2013 14:02:38 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Greg KH <gregkh@...uxfoundation.org>,
	Alex Williamson <alex.williamson@...hat.com>
CC:	linux-kernel@...r.kernel.org, gnomes@...rguk.ukuu.org.uk,
	arnd@...db.de, Alan Cox <alan@...rguk.ukuu.org.uk>
Subject: Re: [PATCH v2] misc: Reserve minor for VFIO

On 12/18/2013 01:01 PM, Greg KH wrote:
> On Wed, Dec 18, 2013 at 01:56:32PM -0700, Alex Williamson wrote:
>> VFIO currently allocates it's own dynamic chardev range, reserving the
>> first minor for the control part of the interface (/dev/vfio/vfio) and
>> the remainder for VFIO groups (/dev/vfio/$GROUP).  This works, but it
>> doesn't support auto loading.  For instance when libvirt checks for
>> VFIO support it looks for /dev/vfio/vfio, which currently doesn't
>> exist unless the vfio module is loaded.  By converting the control
>> device to a misc driver and reserving a static minor, we can enable
>> auto loading.
>>
>> Reserving the minor is a prerequist to that conversion.  Minor 196
>> is unused by anything currently in the kernel.
>>
>> Suggested-by: Paolo Bonzini <pbonzini@...hat.com>
>> Signed-off-by: Alex Williamson <alex.williamson@...hat.com>
>> ---
>>
>> v2: Plea for ack edition
>>
>> As Alan suspected, there's been no response from device@...ana.org,
>> so there's probably nobody monitoring it anymore.  I've done due
>> diligence looking at all the callers of misc_register() in linux-next
>> and cannot find any conflicts with minor 196.  If anyone wants to toss
>> me an ack or sign-off I'll be happy to bring this in through my vfio
>> tree, otherwise I'd appreciate if someone wants to take it directly.
>> Thanks!
>>
>>  Documentation/devices.txt  |    1 +
>>  include/linux/miscdevice.h |    1 +
>>  2 files changed, 2 insertions(+)
> 
> Acked-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> 

I think Alan Cox was the last person to man <device@...ana.org>... Alan,
are you still doing that?  (Otherwise patching the file in the Linux
kernel tree seems eminently sensible... there really isn't any need to
reserve numbers for out-of-tree drivers anymore.  Just another perk of
being in-tree.)

	-hpa


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