Re: [RFC 09/10 v2] v4l2-subdev: re-add s_standby to v4l2_subdev_core_ops

From: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
To: Hans Verkuil <hverkuil@xs4all.nl>
Cc: Linux Media Mailing List <linux-media@vger.kernel.org>,
	Magnus Damm <magnus.damm@gmail.com>,
	Robert Jarzmik <robert.jarzmik@free.fr>,
	Darius Augulis <augulis.darius@gmail.com>,
	Paul Mundt <lethal@linux-sh.org>
Subject: Re: [RFC 09/10 v2] v4l2-subdev: re-add s_standby to v4l2_subdev_core_ops
Date: Fri, 22 May 2009 16:23:36 +0200 (CEST)	[thread overview]
Message-ID: <Pine.LNX.4.64.0905221611160.4418@axis700.grange> (raw)
In-Reply-To: <200905211533.34827.hverkuil@xs4all.nl>

On Thu, 21 May 2009, Hans Verkuil wrote:

> On Friday 15 May 2009 19:20:18 Guennadi Liakhovetski wrote:
> > NOT FOR SUBMISSION. Probably, another solution has to be found.
> > soc-camera drivers need an .init() (marked as "don't use") and a .halt()
> > methods.
> >
> > Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
> > ---
> >
> > Hans, you moved s_standby to tuner_ops, and init is not recommended for
> > new drivers. Suggestions?
> 
> Usual question: why do you need an init and halt? What do they do?

Hm, maybe you're right, I don't need them. init() was used in soc_camera 
drivers on first open() to possibly reset the chip and put it in some 
reasonably pre-defined low-power state. But we can do this at the end of 
probe(), which even would be more correct, because even the first open 
should not change chip's configuration. And halt() (was called release() 
originally) is called on last close(). And it seems you shouldn't really 
do this at all - the chip should preserve its configuration between 
open/close cycles. Am I right? Does anyone among cc'ed authors have any 
objections against this change? The actual disable should indeed migrate 
to some PM functions, if implemented.

Thanks
Guennadi
---
Guennadi Liakhovetski, Ph.D.
Freelance Open-Source Software Developer
http://www.open-technology.de/