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From: Greg KH <greg@kroah.com>
To: Gerd Knorr <kraxel@bytesex.org>
Cc: Kernel List <linux-kernel@vger.kernel.org>,
	video4linux list <video4linux-list@redhat.com>
Subject: Re: [RFC/PATCH] sysfs'ify video4linux
Date: Thu, 17 Jul 2003 14:49:07 -0700	[thread overview]
Message-ID: <20030717214907.GA3255@kroah.com> (raw)
In-Reply-To: <20030717163715.GA19258@bytesex.org>

On Thu, Jul 17, 2003 at 06:37:15PM +0200, Gerd Knorr wrote:
> 
> Version (1) can be done without breaking the build, with a hack along 
> the lines "if (no release callback) printk(KERN_WARN please fix your
> driver)", so the drivers can be fixed step-by-step afterwards.

That sounds like a nice way to start.

> Fixing the drivers might be non-trivial through.  Some drivers are
> hot-pluggable (usb cams), some drivers register more than one v4l device
> (bttv wants up to three).  Those drivers can't just call kfree() in the
> ->release callback because there might be other references, some open
> file handle for a unplugged usb cam, another not-yet unregistered
> v4l device, whatever.  Probably they must implement some reference
> counting scheme to get that right.  The very simple ones (in
> drivers/media/radio for example) likely just need the kfree() moved
> from the ->remove function into the new ->release() callback.

I don't think it will be that bad for them.  Just have them change the
v4l device from being a structure included in their structure, into a
pointer, and then create it before registering, and free it in the
release() callback.

That being said, I haven't actually looked at the code to verify that
this is all that is needed :)

> Version (2) needs every v4l driver touched to make it compile again.
> Not sure how hard it is to fixup them.  I'd guess it is pretty straigt
> forward to do the conversion, it's just alot of work.  I also could do
> a number of other cleanups along the way.  Maybe I trap into some hidden
> pitfalls through, havn't looked at all the drivers in detail yet.

Breaking the build is a very good thing to do at times, to ensure that
stuff gets fixed properly.  Users might go for a while without realizing
that there really is a problem in their driver.

But in the end, it's up to you...

thanks,

greg k-h

  reply	other threads:[~2003-07-17 21:34 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2003-07-15 14:31 [RFC/PATCH] sysfs'ify video4linux Gerd Knorr
2003-07-15 15:21 ` Ronald Bultje
2003-07-15 16:19   ` Matt Porter
2003-07-15 21:27 ` Greg KH
2003-07-16  8:44   ` Gerd Knorr
2003-07-16 16:19     ` Greg KH
2003-07-16 20:20       ` Gerd Knorr
2003-07-16 21:08         ` Greg KH
2003-07-17 12:01           ` Gerd Knorr
2003-07-17 14:57             ` Greg KH
2003-07-17 16:37               ` Gerd Knorr
2003-07-17 21:49                 ` Greg KH [this message]
2003-07-18  9:59                   ` Gerd Knorr
     [not found]                     ` <20030718234359.GK1583@kroah.com>
2003-07-21  7:28                       ` Gerd Knorr
2003-07-21  7:55                         ` Ronald Bultje
2003-07-21 15:43                         ` [RFC/PATCH] 1/2 v4l: sysfs'ify video4linux core Gerd Knorr
2003-07-21 15:47                           ` [RFC/PATCH] 2/2 v4l: sysfs'ify bttv driver Gerd Knorr
2003-07-21 16:27                           ` [RFC/PATCH] 1/2 v4l: sysfs'ify video4linux core Greg KH
2003-07-16 13:33   ` [RFC/PATCH] sysfs'ify video4linux Mark McClelland
2003-07-16 14:10     ` root
2003-07-16 16:23     ` Greg KH

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