Should driver changes cause hotplug event

Should driver changes cause hotplug event

[Jon Smirl]

1) I had radeonfb loaded. It claims my video card.
2) Next I load radeon, it will also claim my video card, but radeonfb is
blocking it, so it loads and doesn't initialize.
3) Now I rmmod radeonfb. 

Should the hotplug system notice this and attach radeon to the hardware since it
is already loaded? I tried and it didn't attach radeon to the hardware.

I don't need this to work, I'm just wondering what's supposed to happen.

==Jon Smirl
jonsmirl@yahoo.com

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Re: Should driver changes cause hotplug event

[Greg KH]

On Sun, Feb 15, 2004 at 09:28:19PM -0800, Jon Smirl wrote:
> 1) I had radeonfb loaded. It claims my video card.
> 2) Next I load radeon, it will also claim my video card, but radeonfb is
> blocking it, so it loads and doesn't initialize.
> 3) Now I rmmod radeonfb. 
> 
> Should the hotplug system notice this and attach radeon to the
> hardware since it is already loaded? I tried and it didn't attach
> radeon to the hardware.

This isn't a hotplug issue.  It's a driver core issue.  Currently the
kernel does not try to match up drivers to any device that just had a
driver removed from it.

It's probably something I'll fix up in 2.7, and if it works well,
consider backporting it to 2.6 (but there are lots of other issues with
devinit sections that will be nasty to track down...)

thanks,

greg k-h


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Re: Should driver changes cause hotplug event

[Oliver Neukum]

Am Montag, 16. Februar 2004 22:04 schrieb Greg KH:
> On Sun, Feb 15, 2004 at 09:28:19PM -0800, Jon Smirl wrote:
> > 1) I had radeonfb loaded. It claims my video card.
> > 2) Next I load radeon, it will also claim my video card, but radeonfb is
> > blocking it, so it loads and doesn't initialize.
> > 3) Now I rmmod radeonfb. 
> > 
> > Should the hotplug system notice this and attach radeon to the
> > hardware since it is already loaded? I tried and it didn't attach
> > radeon to the hardware.
> 
> This isn't a hotplug issue.  It's a driver core issue.  Currently the
> kernel does not try to match up drivers to any device that just had a
> driver removed from it.

Potentially dangerous. There needs to be a way to get a driver off
a device.

	Regards
		Oliver




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Re: Should driver changes cause hotplug event

[Greg KH]

On Tue, Feb 24, 2004 at 11:30:19PM +0100, Oliver Neukum wrote:
> Am Montag, 16. Februar 2004 22:04 schrieb Greg KH:
> > On Sun, Feb 15, 2004 at 09:28:19PM -0800, Jon Smirl wrote:
> > > 1) I had radeonfb loaded. It claims my video card.
> > > 2) Next I load radeon, it will also claim my video card, but radeonfb is
> > > blocking it, so it loads and doesn't initialize.
> > > 3) Now I rmmod radeonfb. 
> > > 
> > > Should the hotplug system notice this and attach radeon to the
> > > hardware since it is already loaded? I tried and it didn't attach
> > > radeon to the hardware.
> > 
> > This isn't a hotplug issue.  It's a driver core issue.  Currently the
> > kernel does not try to match up drivers to any device that just had a
> > driver removed from it.
> 
> Potentially dangerous. There needs to be a way to get a driver off
> a device.

I don't understand.  That would work just the same way as before.  Just
that when we remove a driver off of a device, we might want to check all
other drivers that are currently present in the system to see if they
want to bind to the device.

Something like this will be necessary if we start to add "levels" of
bindness to drivers (kind of like what microsoft has.)  People have been
talking about this being one of the things we do for 2.7.

thanks,

greg k-h


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Re: Should driver changes cause hotplug event

[Oliver Neukum]

Am Donnerstag, 26. Februar 2004 18:57 schrieb Greg KH:
> On Tue, Feb 24, 2004 at 11:30:19PM +0100, Oliver Neukum wrote:
> > Am Montag, 16. Februar 2004 22:04 schrieb Greg KH:
> > > On Sun, Feb 15, 2004 at 09:28:19PM -0800, Jon Smirl wrote:
> > > > 1) I had radeonfb loaded. It claims my video card.
> > > > 2) Next I load radeon, it will also claim my video card, but radeonfb is
> > > > blocking it, so it loads and doesn't initialize.
> > > > 3) Now I rmmod radeonfb. 
> > > > 
> > > > Should the hotplug system notice this and attach radeon to the
> > > > hardware since it is already loaded? I tried and it didn't attach
> > > > radeon to the hardware.
> > > 
> > > This isn't a hotplug issue.  It's a driver core issue.  Currently the
> > > kernel does not try to match up drivers to any device that just had a
> > > driver removed from it.
> > 
> > Potentially dangerous. There needs to be a way to get a driver off
> > a device.
> 
> I don't understand.  That would work just the same way as before.  Just
> that when we remove a driver off of a device, we might want to check all
> other drivers that are currently present in the system to see if they
> want to bind to the device.

But, as David has convinced me, there needs to be a way to make sure
that a device is bound to no driver. Currently we have some halfassed way
of doing this for USB. It will work while you don't load new modules.

> Something like this will be necessary if we start to add "levels" of
> bindness to drivers (kind of like what microsoft has.)  People have been
> talking about this being one of the things we do for 2.7.

Yes, but think of user space drivers. If you really want to do this, you
need a way of claiming devices from user space. This opens a new can of
worms. You need hooks in exit() to give up such claims in case of unplanned
termination.

	Regards
		Oliver



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