linux-kernel - Re: AGPGart / AMD K7

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Date:	Fri, 20 Apr 2007 14:20:29 -0400
From:	Dave Jones <davej@...hat.com>
To:	"Preston A. Elder" <prez@...h.net>
Cc:	linux-kernel@...r.kernel.org, greg@...ah.com
Subject: Re: AGPGart / AMD K7

On Fri, Apr 20, 2007 at 02:04:45PM -0400, Preston A. Elder wrote:
 > Dave Jones wrote:
 > > On Fri, Apr 20, 2007 at 12:53:31PM -0400, Preston A. Elder wrote:
 > >
 > >  > Linux agpgart interface v0.101 (c) Dave Jones
 > >  > agpgart: DEBUG 0
 > >  > agpgart: DEBUG 1
 > >  > __pci_register_driver: In function
 > >  > __pci_register_driver: driver = agpgart-amdk7, multithread = 0
 > >  > __pci_register_driver: Before Spinlock
 > >  > __pci_register_driver: Before List Init
 > >  > __pci_register_driver: Before Driver Register
 > >  > __pci_register_driver: Error = 0
 > >  > __pci_register_driver: Returning 0
 > >  > 
 > >  > The DEBUG 0 and 1 are coming from agp_amdk7_init()
 > >  > There is a DEBUG 2 at the top of agp_amdk7_probe(), even before
 > >  > pci_find_capability, but the function never gets called.
 > >
 > > bus_add_driver() returns 0 on error, but there's a few different
 > > cases it can fail, which isn't helpful.

Actually I misparsed this function, see below..

 > > Add some printk's to
 > > the error cases there, and see if that gives any more clues.
 > >
 > Here you go:

This is odd..

 > >  > __pci_register_driver: Before Driver Register
 > >  > __pci_register_driver: Error = 0
 > >  > __pci_register_driver: Returning 0

That __pci_register_driver code is (presumably with your printk's added..)

        error = driver_register(&drv->driver);
	printk("Error = %d\n", error);
        if (error) {
		printk("Returning %d\n" error);
                return error;
	}

Which doesn't make much sense.  If 'error' is 0, we shouldn't be
taking that second printk & return. What compiler version is this?

btw Greg, wtf does driver_register return a 0 as 'success' if it
completes the function, and 0 as 'failure' if !bus ?
That seems doomed to failure.

 > Linux agpgart interface v0.101 (c) Dave Jones
 > agpgart: DEBUG 0
 > agpgart: DEBUG 1
 > __pci_register_driver: In function
 > __pci_register_driver: driver = agpgart-amdk7, multithread = 0
 > __pci_register_driver: Before Spinlock
 > __pci_register_driver: Before List Init
 > __pci_register_driver: Before Driver Register
 > bus_add_driver: In Function
 > bus_add_driver: Before kobject_set_name (agpgart-amdk7)
 > bus_add_driver: error = 0
 > bus_add_driver: Before kobject_register
 > bus_add_driver: error = 0
 > bus_add_driver: Before driver_attach
 > bus_add_driver: error = 0
 > bus_add_driver: Before klist_add_tail
 > bus_add_driver: Before module_add_driver
 > bus_add_driver: Before driver_add_attrs
 > bus_add_driver: error = 0
 > bus_add_driver: Before add_bind_files
 > bus_add_driver: error = 0
 > bus_add_driver: Returning 0
 > __pci_register_driver: Error = 0
 > __pci_register_driver: Returning 0

So we completed bus_add_driver without failing, then popped back
up to __pci_register_driver and were somehow treated as
if we failed.   *scratches head*

	Dave

-- 
http://www.codemonkey.org.uk
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