Re: [PATCH 1/3] atomisp: Fix up the open v load race

[Alan Cox <gnomes@lxorguk.ukuu.org.uk>]

On Tue, 12 Dec 2017 09:03:50 -0200
Mauro Carvalho Chehab <mchehab@s-opensource.com> wrote:

> Em Mon, 06 Nov 2017 23:36:36 +0000
> Alan <alan@linux.intel.com> escreveu:
> 
> > This isn't the ideal final solution but it stops the main problem for now
> > where an open (often from udev) races the device initialization and we try
> > and load the firmware twice at the same time. This needless to say doesn't
> > usually end well.  
> 
> What we do on most drivers is that video_register_device() is called
> only after all hardware init.
> 
> That's usually enough to avoid race conditions with udev, although
> a mutex is also common in order to avoid some other race conditions
> between open/close - with can happen with multiple opens.

There are a whole bunch of other ordering issues to deal with in the
atomisp case beyond this - another one is that the camera probe can race
the ISP probe.

Quite a lot of the registration code needs fixing, but I'm prioritizing
stabilizing the code first, and trying to get the Cherrytrail version
going.

Alan