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

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

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Hi.

On Fri, 2007-04-27 at 08:40 -0700, Greg KH wrote:
> On Fri, Apr 27, 2007 at 03:25:46PM +0300, 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.
> > 
> > Cc: Pavel Machek <pavel@ucw.cz>
> > Cc: Rafael J. Wysocki <rjw@sisk.pl>
> > Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
> > ---
> >  drivers/base/core.c       |   13 +++++++++++++
> >  drivers/pci/pci-driver.c  |    6 ++++++
> >  drivers/usb/core/driver.c |    6 ++++++
> >  include/linux/device.h    |    1 +
> >  4 files changed, 26 insertions(+)
> > 
> > Index: 2.6/drivers/base/core.c
> > ===================================================================
> > --- 2.6.orig/drivers/base/core.c	2007-04-27 14:42:13.000000000 +0300
> > +++ 2.6/drivers/base/core.c	2007-04-27 14:43:14.000000000 +0300
> > @@ -652,6 +652,18 @@ int device_add(struct device *dev)
> >  				class_intf->add_dev(dev, class_intf);
> >  		up(&dev->class->sem);
> >  	}
> > +
> > +#ifdef CONFIG_PM
> > +	if (!((dev->class && dev->class->resume) ||
> > +	      (dev->bus && (dev->bus->resume || dev->bus->resume_early))) &&
> > +	    !dev->pm_safe) {
> > +		printk(KERN_WARNING "Device driver %s lacks bus and class "
> > +				    "support for being resumed.\n",
> > +				    kobject_name(&dev->kobj));
> > +		dump_stack();
> > +	}
> > +#endif
> 
> 
> I think you are reporting the wrong thing here, we want to know about
> the busses and classes without suspend support, not the individual
> devices, right?

Yeah, I suppose you're right. I started off seeking to make a message
for each device lacking anything that would save its state. Guess I got
muddled somewhere :)

> And dumping stuff like this to the log for every bus/class isn't the
> nicest :(
> 
> 
> > +
> >   Done:
> >   	kfree(class_name);
> >  	put_device(dev);
> > @@ -989,6 +1001,7 @@ struct device *device_create(struct clas
> >  	dev->class = class;
> >  	dev->parent = parent;
> >  	dev->release = device_create_release;
> > +	dev->pm_safe = 1;
> 
> I don't understand the use of this flag, it looks like it is only being
> set, which doesn't really make it very useful.

The use was above (!dev->pm_safe).

Regards,

Nigel


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