linux-kernel - Re: [PATCH 1/2] Documentation: Bump media IOCTL reserved numbers

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Message-ID: <aDRriOnRfEYPeziC@kekkonen.localdomain>
Date: Mon, 26 May 2025 13:24:24 +0000
From: Sakari Ailus <sakari.ailus@...ux.intel.com>
To: Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc: linux-doc@...r.kernel.org, Jonathan Corbet <corbet@....net>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Madhavan Srinivasan <maddy@...ux.ibm.com>,
	Haren Myneni <haren@...ux.ibm.com>,
	Bagas Sanjaya <bagasdotme@...il.com>,
	Andrew Donnellan <ajd@...ux.ibm.com>,
	Michael Ellerman <mpe@...erman.id.au>,
	Akshay Gupta <akshay.gupta@....com>, linux-kernel@...r.kernel.org,
	linux-media@...r.kernel.org, hans@...erkuil.nl,
	Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
	Lee Jones <lee@...nel.org>
Subject: Re: [PATCH 1/2] Documentation: Bump media IOCTL reserved numbers

Hi Laurent,

On Mon, May 26, 2025 at 01:48:02PM +0200, Laurent Pinchart wrote:
> Hi Sakari,
> 
> Thank you for the patch.

Thank you for the review.

> 
> On Mon, May 26, 2025 at 02:17:31PM +0300, Sakari Ailus wrote:
> > The Media Controller uses IOCTL numbers up to 0x81. Given that nothing
> > appears to be using them for other purposes, even in the samples
> > allocation (checked with $ git grep "#define.*_IO.*'|'"), just reassign
> > the numbers up to 0x8f to linux/media.h and bump the samples allocation by
> > 0x10.
> 
> The commit message should explain why. The explanation is in the cover
> letter, just move it to this patch. With that,
> 
> Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>

I'll use this in v2:

The Media Controller uses IOCTL type '|' with numbers up to 0x81 while
numbers from 0x80 onwards are allocated for samples, creating a conflict
between allocations for MC and samples. Given that nothing appears to be
using numbers between 0x80 and 0x8f for other purposes than MC, even in
the samples allocation (checked with $ git grep "#define.*_IO.*'|'"), just
reassign the numbers up to 0x8f to linux/media.h and bump the samples
allocation by 0x10.

> 
> > Signed-off-by: Sakari Ailus <sakari.ailus@...ux.intel.com>
> > ---
> >  Documentation/userspace-api/ioctl/ioctl-number.rst | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/Documentation/userspace-api/ioctl/ioctl-number.rst b/Documentation/userspace-api/ioctl/ioctl-number.rst
> > index bc91756bde73..6b3be3fb0b15 100644
> > --- a/Documentation/userspace-api/ioctl/ioctl-number.rst
> > +++ b/Documentation/userspace-api/ioctl/ioctl-number.rst
> > @@ -312,8 +312,8 @@ Code  Seq#    Include File                                           Comments
> >  'z'   40-7F                                                          CAN bus card conflict!
> >                                                                       <mailto:oe@...t.de>
> >  'z'   10-4F  drivers/s390/crypto/zcrypt_api.h                        conflict!
> > -'|'   00-7F  linux/media.h
> > -'|'   80-9F  samples/                                                Any sample and example drivers
> > +'|'   00-8F  linux/media.h
> > +'|'   90-AF  samples/                                                Any sample and example drivers
> >  0x80  00-1F  linux/fb.h
> >  0x81  00-1F  linux/vduse.h
> >  0x89  00-06  arch/x86/include/asm/sockios.h
> 

-- 
Regards,

Sakari Ailus