dri and udev

dri and udev

[Jon Smirl]

I've been working on the dri drivers to make them appear in sysfs and udev. I
have it all working now using the simple_add_class_device() routine. The dri
device is normally found in /dev/dri/card0, /dev/dri/card1, etc. How do I make
the device appear in a subdir under udev?

==Jon Smirl
jonsmirl@yahoo.com

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Re: dri and udev

[Kay Sievers]

On Fri, Dec 26, 2003 at 11:24:25PM -0800, Jon Smirl wrote:
> I've been working on the dri drivers to make them appear in sysfs and udev. I
> have it all working now using the simple_add_class_device() routine. The dri
> device is normally found in /dev/dri/card0, /dev/dri/card1, etc. How do I make
> the device appear in a subdir under udev?

You may try NAME="dev/dri/card0", it will create the subdirs for you.
Examples are in the file udev.rules.devfs.

Kay


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Re: dri and udev

[Jon Smirl]

Adding:
REPLACE, KERNEL="card*", NAME="dri/card%n"
to udev rules makes it work.

DRI sure made an unfortunate legacy choice of calling the driver cardX.

How is this going to work when there are multiple devices with the same name?
For example
/dev/hda and /dev/i2o/hda?

--- Kay Sievers <kay.sievers@vrfy.org> wrote:
> On Fri, Dec 26, 2003 at 11:24:25PM -0800, Jon Smirl wrote:
> > I've been working on the dri drivers to make them appear in sysfs and udev.
> I
> > have it all working now using the simple_add_class_device() routine. The dri
> > device is normally found in /dev/dri/card0, /dev/dri/card1, etc. How do I
> make
> > the device appear in a subdir under udev?
> 
> You may try NAME="dev/dri/card0", it will create the subdirs for you.
> Examples are in the file udev.rules.devfs.
> 
> Kay


==Jon Smirl
jonsmirl@yahoo.com

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Re: dri and udev

[Greg KH]

On Sat, Dec 27, 2003 at 09:08:57AM -0800, Jon Smirl wrote:
> Adding:
> REPLACE, KERNEL="card*", NAME="dri/card%n"
> to udev rules makes it work.
> 
> DRI sure made an unfortunate legacy choice of calling the driver cardX.
> 
> How is this going to work when there are multiple devices with the same name?
> For example
> /dev/hda and /dev/i2o/hda?

Those are two different devices, with different major/minor numbers.
i2o can't create a hda block device if there is already a block device
called hda in the system.  So it will be called something else.  As i2o
isn't working yet in 2.6, I'm not to worried about it :)

thanks,

greg k-h


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Re: dri and udev

[Greg KH]

On Sat, Dec 27, 2003 at 09:08:57AM -0800, Jon Smirl wrote:
> Adding:
> REPLACE, KERNEL="card*", NAME="dri/card%n"
> to udev rules makes it work.
> 
> DRI sure made an unfortunate legacy choice of calling the driver cardX.
> 
> How is this going to work when there are multiple devices with the same name?
> For example
> /dev/hda and /dev/i2o/hda?

Those are two different devices, with different major/minor numbers.
i2o can't create a hda block device if there is already a block device
called hda in the system.  So it will be called something else.  As i2o
isn't working yet in 2.6, I'm not to worried about it :)

thanks,

greg k-h


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Re: dri and udev

[Greg KH]

On Sat, Dec 27, 2003 at 09:08:57AM -0800, Jon Smirl wrote:
> Adding:
> REPLACE, KERNEL="card*", NAME="dri/card%n"
> to udev rules makes it work.
> 
> DRI sure made an unfortunate legacy choice of calling the driver cardX.
> 
> How is this going to work when there are multiple devices with the same name?
> For example
> /dev/hda and /dev/i2o/hda?

Those are two different devices, with different major/minor numbers.
i2o can't create a hda block device if there is already a block device
called hda in the system.  So it will be called something else.  As i2o
isn't working yet in 2.6, I'm not to worried about it :)

thanks,

greg k-h


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Re: dri and udev

[Greg KH]

On Fri, Dec 26, 2003 at 11:24:25PM -0800, Jon Smirl wrote:
> I've been working on the dri drivers to make them appear in sysfs and udev. I
> have it all working now using the simple_add_class_device() routine.

Great, care to send me the kernel patch for this?

thanks,

greg k-h


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Re: dri and udev

[Jon Smirl]

The new DRM module has other changes in it so it has to be sync'd with a
DRI/Xfree86 release.  I also have to get the changes coordinated with the BSD
DRI people. DRM development happens out of the DRI tree not the kernel tree. So
after there is a DRI/Xfree86 Linus moves the changes over to the copy in the
kernel.

Another issue is the current conflict between fbdev and dri. Both device drivers
are trying to take overship of the graphics hardware. Right now fbdev owns the
hardware and DRI operates as a stealth module. For sysfs/udev to work DRI has to
have a PCI ID table and own the hardware. Doing this prevents fbdev and DRI from
simultaneously being loaded. 

This conflict has not been resolved. We did a previous version of DRM which
registered with the kernel as owning the hardware and got a lot of vocal
complaints from fbdev developers. DRM was backed off into steath mode again.

Stealth mode looks like this. It never calls pci_register_driver so the kernel
never knows that DRM has attached to the device.

static int __init drm_init( void )
{
	struct pci_dev *pdev = NULL;

	DRM(parse_options)( drm_opts );
	DRM(mem_init)();

	while ((pdev = pci_find_device(PCI_ANY_ID, PCI_ANY_ID, pdev)) != NULL) {
		DRM(probe)(pdev);
	}
	return 0;
}

My personal opinion on this is that it is insane for two device drivers to be
trying to share the same same piece of hardware - it's multitasking for device
drivers. I also don't think udev/sysfs are set up to deal with two device
drivers claiming the same piece of hardware.


==Jon Smirl
jonsmirl@yahoo.com

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Re: dri and udev

[Jon Smirl]

The new DRM module has other changes in it so it has to be sync'd with a
DRI/Xfree86 release.  I also have to get the changes coordinated with the BSD
DRI people. DRM development happens out of the DRI tree not the kernel tree. So
after there is a DRI/Xfree86 Linus moves the changes over to the copy in the
kernel.

Another issue is the current conflict between fbdev and dri. Both device drivers
are trying to take overship of the graphics hardware. Right now fbdev owns the
hardware and DRI operates as a stealth module. For sysfs/udev to work DRI has to
have a PCI ID table and own the hardware. Doing this prevents fbdev and DRI from
simultaneously being loaded. 

This conflict has not been resolved. We did a previous version of DRM which
registered with the kernel as owning the hardware and got a lot of vocal
complaints from fbdev developers. DRM was backed off into steath mode again.

Stealth mode looks like this. It never calls pci_register_driver so the kernel
never knows that DRM has attached to the device.

static int __init drm_init( void )
{
	struct pci_dev *pdev = NULL;

	DRM(parse_options)( drm_opts );
	DRM(mem_init)();

	while ((pdev = pci_find_device(PCI_ANY_ID, PCI_ANY_ID, pdev)) != NULL) {
		DRM(probe)(pdev);
	}
	return 0;
}

My personal opinion on this is that it is insane for two device drivers to be
trying to share the same same piece of hardware - it's multitasking for device
drivers. I also don't think udev/sysfs are set up to deal with two device
drivers claiming the same piece of hardware.


==Jon Smirl
jonsmirl@yahoo.com

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Re: dri and udev

[Marco d'Itri]

On Dec 27, Jon Smirl <jonsmirl@yahoo.com> wrote:

 >My personal opinion on this is that it is insane for two device drivers to be
 >trying to share the same same piece of hardware - it's multitasking for device
 >drivers. I also don't think udev/sysfs are set up to deal with two device
 >drivers claiming the same piece of hardware.
I fully agree. This also has the downside that hotplug cannot
automatically load the DRM modules.
(And probably many more people need DRM than they need fbdev...)

-- 
ciao, |
Marco | [3810 esbuHOWw6GXX6]


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Re: dri and udev

[Marco d'Itri]

On Dec 27, Jon Smirl <jonsmirl@yahoo.com> wrote:

 >My personal opinion on this is that it is insane for two device drivers to be
 >trying to share the same same piece of hardware - it's multitasking for device
 >drivers. I also don't think udev/sysfs are set up to deal with two device
 >drivers claiming the same piece of hardware.
I fully agree. This also has the downside that hotplug cannot
automatically load the DRM modules.
(And probably many more people need DRM than they need fbdev...)

-- 
ciao, |
Marco | [3810 esbuHOWw6GXX6]


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Re: dri and udev

[Greg KH]

On Sat, Dec 27, 2003 at 12:57:38PM -0800, Jon Smirl wrote:
> 
> 	while ((pdev = pci_find_device(PCI_ANY_ID, PCI_ANY_ID, pdev)) != NULL) {

If you _have_ to do this, please use pci_get_device() instead.  It's
much safer to use.

> My personal opinion on this is that it is insane for two device drivers to be
> trying to share the same same piece of hardware - it's multitasking for device
> drivers. I also don't think udev/sysfs are set up to deal with two device
> drivers claiming the same piece of hardware.

The driver model is not set up to do that.  And it is correct, you
should claim the device, like the fbdev people do.  If users want one or
the other, that's fine.  Bad things might happen if two drivers talk to
the same hardware at the same time.

thanks,

greg k-h


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