Re: [RFC/PATCH 2/2] driver core: power management debugging

[Nigel Cunningham <nigel@nigel.suspend2.net>]

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Hi Alan.

On Fri, 2007-04-27 at 10:08 -0400, Alan Stern wrote:
> On Fri, 27 Apr 2007, Pekka J Enberg wrote:
> 
> > From: Nigel Cunningham <nigel@nigel.suspend2.net>
> > 
> > Add power management related debugging into driver core. Make the
> > kernel complain if a device driver lacks bus and class support for
> > resume or if a PCI or USB driver does not have a driver specific
> > resume function.
> 
> > Index: 2.6/drivers/usb/core/driver.c
> > ===================================================================
> > --- 2.6.orig/drivers/usb/core/driver.c	2007-04-27 14:42:13.000000000 +0300
> > +++ 2.6/drivers/usb/core/driver.c	2007-04-27 14:43:14.000000000 +0300
> > @@ -721,6 +721,12 @@ 	int retval = 0;
> >  		pr_info("%s: registered new device driver %s\n",
> >  			usbcore_name, new_udriver->name);
> >  		usbfs_update_special();
> > +#ifdef CONFIG_PM
> > +		if (!new_udriver->resume)
> > +			printk(KERN_WARNING "USB driver %s lacks driver "
> > +					    "specific resume support.\n",
> > +					    new_udriver->name);
> > +#endif
> >  	} else {
> >  		printk(KERN_ERR "%s: error %d registering device "
> >  			"	driver %s\n",
> 
> This part seems unnecessary.  There is only one USB device driver, it is
> built into the USB core, and it does have the appropriate methods.  
> Checking isn't needed.

Sorry. I thought you were wrong for a minute, but then I looked again at
the messages in my dmesg...

[   33.944214] Device driver usbdev1.1_ep00 lacks bus and class support for being resumed.
[   34.051765] Device driver usbdev1.1_ep81 lacks bus and class support for being resumed.
[   34.113740] Device driver usbdev2.1_ep00 lacks bus and class support for being resumed.
[   34.221541] Device driver usbdev2.1_ep81 lacks bus and class support for being resumed.
[   34.251562] Device driver usbdev3.1_ep00 lacks bus and class support for being resumed.
[   34.361345] Device driver usbdev3.1_ep81 lacks bus and class support for being resumed.

They're coming from the other printk, of course.

> Now perhaps you would prefer to check the USB interface drivers -- there 
> are many of them, and quite a few don't have suspend or resume methods.  
> You would need to modify usb_register_driver() instead of 
> usb_register_device_driver().

Would they be the ones covered above?

> On the other hand, the drivers' maintainers are probably quite aware of 
> the missing PM support, so it's not clear that printing out warning 
> messages will actually help anybody.

It can help the user, when they're looking for possibilities as to why things aren't working.

Regards,

Nigel

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