linux-kernel - Re: [PATCH v2 0/3] Document Media Controller IOCTL number assignments

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Message-ID: <aLrDWyxiiF2hPu_8@valkosipuli.retiisi.eu>
Date: Fri, 5 Sep 2025 14:02:51 +0300
From: Sakari Ailus <sakari.ailus@....fi>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: linux-doc@...r.kernel.org, Jonathan Corbet <corbet@....net>,
	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,
	laurent.pinchart@...asonboard.com,
	Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
	Lee Jones <lee@...nel.org>
Subject: Re: [PATCH v2 0/3] Document Media Controller IOCTL number assignments

Hi Greg,

On Fri, Sep 05, 2025 at 12:32:45PM +0200, Greg Kroah-Hartman wrote:
> On Fri, Sep 05, 2025 at 01:25:33PM +0300, Sakari Ailus wrote:
> > Hi Jonathan, Greg, Miguel, others,
> > 
> > On Tue, May 27, 2025 at 08:56:45AM +0300, Sakari Ailus wrote:
> > > Hello all,
> > > 
> > > The Media Controller uses IOCTL numbers with '|' type up to 0x81 but the
> > > range from 0x80 upwards is documented to belong to samples. The samples,
> > > however, are currently using these values. Solve the problem by bumping
> > > the top of the MC range and the samples allocation by 0x10 as the samples
> > > don't require a stable IOCTL interface.
> > 
> > Could you comment on this, please?
> 
> Why not just live with the overlap?  What problem is this causing?  It's
> the MC subsystem's "bug" in that it took over an ioctl range that was
> already documented as being used by something else :)

I do agree ideally this shouldn't have happened in the first place, but I
think it's also cleaner if we can have separate ranges. Pushing samples out
a little doesn't look like an issue to me. The set also adds a comment on
not adding media IOCTLs beyond the new allocation.

-- 
Kind regards,

Sakari Ailus