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From: Gerd Knorr <>
To: Greg KH <>
Cc: Kernel List <>,
	video4linux list <>
Subject: Re: [RFC/PATCH] sysfs'ify video4linux
Date: Wed, 16 Jul 2003 22:20:18 +0200	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

> It looks like the video drivers include a "struct video_device"
> structure within their own structures, right?

Yes, it is allocated/freed by the driver, most seem to simply include
one ore more "struct video_device" somewhere in the per-device struct.

> That will have to be changed to a pointer to that structure in order
> for the lifetime rules to work properly.

Hmm.  I doubt it will be that simple.  struct video_device has a priv
field which can be used by the drivers to hook in some driver-private
data.  That may point into nowhere if struct video_device has a longer
live time due to some kobject still being referenced.  Wouldn't be a
issue for videodev.o itself, but might become a problem for drivers
which want add private properties and rely on video_device->priv
for finding the per-device data.  Problem isn't solved but justed
moved to the next corner ...

Maybe let video_unregister sleep on a semaphore which gets woken up
by the release function?  That should make sure the sysfs objects are
not referenced any more if video_unregister() returns.  I use a similar
method in some places when shutting down kernel threads, to make sure it
is really stopped before rmmod frees the memory.

> Look at the dev file in /sys/class/tty/*, or in /sys/block/hd* or in
> /sys/class/usb/*, and so on...

I've found the code in drivers/block/genhd.c in the meantime :)



  reply	other threads:[~2003-07-16 20:10 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 [this message]
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
2003-07-18  9:59                   ` Gerd Knorr
     [not found]                     ` <>
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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