Re: [RFC][PATCH] add driver matching priorities

[Greg KH <greg@kroah.com>]

On Thu, Feb 10, 2005 at 12:18:37PM -0500, Adam Belay wrote:
> On Thu, 2005-02-10 at 00:41 -0800, Greg KH wrote:
> > On Fri, Jan 28, 2005 at 05:30:04PM -0500, Adam Belay wrote:
> > > Hi,
> > > 
> > > This patch adds initial support for driver matching priorities to the
> > > driver model.  It is needed for my work on converting the pci bridge
> > > driver to use "struct device_driver".  It may also be helpful for driver
> > > with more complex (or long id lists as I've seen in many cases) matching
> > > criteria. 
> > > 
> > > "match" has been added to "struct device_driver".  There are now two
> > > steps in the matching process.  The first step is a bus specific filter
> > > that determines possible driver candidates.  The second step is a driver
> > > specific match function that verifies if the driver will work with the
> > > hardware, and returns a priority code (how well it is able to handle the
> > > device).  The bus layer could override the driver's match function if
> > > necessary (similar to how it passes *probe through it's layer and then
> > > on to the actual driver).
> > > 
> > > The current priorities are as follows:
> > > 
> > > enum {
> > > 	MATCH_PRIORITY_FAILURE = 0,
> > > 	MATCH_PRIORITY_GENERIC,
> > > 	MATCH_PRIORITY_NORMAL,
> > > 	MATCH_PRIORITY_VENDOR,
> > > };
> > > 
> > > let me know if any of this would need to be changed.  For example, the
> > > "struct bus_type" match function could return a priority code.
> > > 
> > > Of course this patch is not going to be effective alone.  We also need
> > > to change the init order.  If a driver is registered early but isn't the
> > > best available, it will be bound to the device prematurely.  This would
> > > be a problem for carbus (yenta) bridges.
> > > 
> > > I think we may have to load all in kernel drivers first, and then begin
> > > matching them to hardware.  Do you agree?  If so, I'd be happy to make a
> > > patch for that too.
> > 
> > I think the issue that Al raises about drivers grabbing devices, and
> > then trying to unbind them might be a real problem.
> 
> I agree.  Do you think registering every in-kernel driver before probing
> hardware would solve this problem?

This doesn't work for any vendor kernel as they build all drivers as
modules :(

thanks,

greg k-h