mga_vid

mga_vid

[gilles]

Hello.

The video player "MPlayer" is provided with a kernel module that enhances
performance for some Matrox graphics cards.

Without udev, one should manually create a device node with
# mknod /dev/mga_vid c 178 0

I've placed the module name in /etc/modules, and 'something' is going on,
according to the following:

$ find /sys/ -name '*mga*' -print
/sys/cdev/major/mga_vid

$ ls -l /sys/cdev/major/mga_vid
total 0
drwxr-xr-x    2 root     root            0 Mar 22 14:11 .
drwxr-xr-x   13 root     root            0 Mar 22 15:10 ..

$ ls -l /etc/udev/.dev/mga_vid
crw-rw-r--    1 root     video    178,   0 Feb 26  2002 /etc/udev/.dev/mga_vid

but there is no '/dev/mga_vid'.
With udev, what would be required to set it up?

Best regards,
Gilles


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Re: mga_vid

[Greg KH]

On Mon, Mar 22, 2004 at 11:14:40PM +0100, gilles@harfang.homelinux.org wrote:
> 
> $ ls -l /sys/cdev/major/mga_vid

There is no /sys/cdev in the kernel anymore, thankfully :)

> but there is no '/dev/mga_vid'.
> With udev, what would be required to set it up?

The kernel driver needs to be modified to use sysfs.  Where is the
source for this kernel driver?  Is it in the main kernel tree?

thanks,

greg k-h


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Re: mga_vid

[Frédéric L. W. Meunier]

On Mon, 22 Mar 2004, Greg KH wrote:

> On Mon, Mar 22, 2004 at 11:14:40PM +0100, gilles@harfang.homelinux.org wrote:
> >
> > $ ls -l /sys/cdev/major/mga_vid
>
> There is no /sys/cdev in the kernel anymore, thankfully :)
>
> > but there is no '/dev/mga_vid'.
> > With udev, what would be required to set it up?
>
> The kernel driver needs to be modified to use sysfs.  Where is the
> source for this kernel driver?  Is it in the main kernel tree?

MPlayer. SVGAlib needs too to be modified since it has a
svgalib_helper module that creates /dev/svga.

-- 
http://www.pervalidus.net/contact.html


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Re: mga_vid

[gilles]

> > >
> > > $ ls -l /sys/cdev/major/mga_vid
> >
> > There is no /sys/cdev in the kernel anymore, thankfully :)
> >

I'm not versed in kernel programming, so I can't appreciate
this feeling of relief. :-}

> > > but there is no '/dev/mga_vid'.
> > > With udev, what would be required to set it up?
> >
> > The kernel driver needs to be modified to use sysfs.

Is it a lot of work?
Is there a standard way to proceed [Like: you should find <this>
and replace it with <that>] ?  Is it explained somewhere?

> > Where is the
> > source for this kernel driver?  Is it in the main kernel tree?
> 
> MPlayer. SVGAlib needs too to be modified since it has a
> svgalib_helper module that creates /dev/svga.
> 

From the module source 'README':
 [...]
         mga_vid is a kernel module that utilitizes the Matrox g200/g400 video
         scaler/overlay unit to perform YUV->RGB colorspace conversion and
         arbitrary video scaling.
                                                                                          
         mga_vid is also a monster hack.
 [...]                                                                                          

The code provided in the MPlayer source tree doesn't work anymore with
kernel 2.6, and someone named Brian Hall made the necessary modifications
in a separate tarball.
Shall I send it to you?

Gilles


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Re: mga_vid

[Greg KH]

On Tue, Mar 23, 2004 at 02:00:18PM +0100, gilles@harfang.homelinux.org wrote:
> > > > but there is no '/dev/mga_vid'.
> > > > With udev, what would be required to set it up?
> > >
> > > The kernel driver needs to be modified to use sysfs.
> 
> Is it a lot of work?

Not really, only 3-10 lines of code need to be added to the driver.

> Is there a standard way to proceed [Like: you should find <this>
> and replace it with <that>] ?  Is it explained somewhere?

I've documented it a number of times in the linux-kernel archives.
Basically you need to add a class_simple structure, and add devices to
that structure when needed.  See the drivers/base/class_simple.c code
for information on the API, and any of the drivers that use that
interface for examples of how to use it (like drivers/char/misc.c or
drivers/char/mem.c).

Hope this helps,

greg k-h


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