How to "detach" a foreign driver from a device so my driver can attach?

[John Baldwin]

On Tuesday 23 December 2008 12:33:22 pm Andre Albsmeier wrote:
> On Wed, 17-Dec-2008 at 00:04:30 +0100, Andre Albsmeier wrote:
> > Hello all,
> > 
> > I am writing a driver which attaches to the Host-PCI bridge. When
> > compiled into the kernel or loaded by the loader everything works
> > and the driver gets attached. This is due to the fact that I return
> > BUS_PROBE_SPECIFIC in my probe routine which gains over the -10000
> > returned by pci_hostb_probe() in i386/pci/pci_bus.c.
> > 
> > However, when I want to load my driver via kldload this fails since
> > the hostb device has already been attached during kernel load (when
> > my driver was not present):
> > 
> > hostb0 at pci0:0:0:    class=0x060000 card=0x11d510cf chip=0x35808086 
rev=0x02 hdr=0x00
> > 
> > What can I do to make my driver load via kldload?
> > Is there a way to detach the hostb0 from the Host-PCI bridge?
> 
> Found the answer myself but will post it here in case anyone
> got a similar problem one day: I added the device detach method
> for the hostb driver to sys/i386/pci/pci_bus.c:
> 
> --- sys/i386/pci/pci_bus.c.ORI	2007-08-17 08:12:33.000000000 +0200
> +++ sys/i386/pci/pci_bus.c	2008-12-23 13:34:35.000000000 +0100
> @@ -619,10 +619,13 @@
>  	return 0;
>  }
>  
> +static int pci_hostb_detach(device_t dev) { return 0; }
> +
>  static device_method_t pci_hostb_methods[] = {
>  	/* Device interface */
>  	DEVMETHOD(device_probe,		pci_hostb_probe),
>  	DEVMETHOD(device_attach,	pci_hostb_attach),
> +	DEVMETHOD(device_detach,	pci_hostb_detach),
>  	DEVMETHOD(device_shutdown,	bus_generic_shutdown),
>  	DEVMETHOD(device_suspend,	bus_generic_suspend),
>  	DEVMETHOD(device_resume,	bus_generic_resume),
> 
> Now, when kldload'ing my driver, it can walk through all devices
> and detach hostb using device_detach().

In the case of hostb, this is wrong however.  You want to attach as a child of 
hostb as other devices (e.g. agp(4)) need to attach to host-pci bridges as 
well.

-- 
John Baldwin