Re: [PATCH 2/2] PCI PM: Introduce pci_preferred_state

["Rafael J. Wysocki" <rjw@sisk.pl>]

On Wednesday, 7 of May 2008, Pavel Machek wrote:
> Hi!
> 
> > From: Rafael J. Wysocki <rjw@sisk.pl>
> > 
> > The new suspend and hibernation callbacks introduced with
> > 'struct pm_ops' and 'struct pm_ext_ops' do not take a
> > pm_message_t argument, so the drivers using them will not be able
> > to use pci_choose_state() in its present form.  For this reason,
> > introduce the new function pci_preferred_state() playing the role
> > of pci_choose_state(), but taking only a pointer to the device
> > object.
> > 
> > Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
> > ---
> >  drivers/pci/pci.c   |   33 ++++++++++++++++++++++++++++++++-
> >  include/linux/pci.h |    1 +
> >  include/linux/pm.h  |   10 ++++++++++
> >  3 files changed, 43 insertions(+), 1 deletion(-)
> > 
> > Index: linux-2.6/drivers/pci/pci.c
> > ===================================================================
> > --- linux-2.6.orig/drivers/pci/pci.c
> > +++ linux-2.6/drivers/pci/pci.c
> > @@ -509,7 +509,38 @@ pci_set_power_state(struct pci_dev *dev,
> >  }
> >  
> >  pci_power_t (*platform_pci_choose_state)(struct pci_dev *dev);
> > - 
> > +
> > +/**
> > + * pci_preferred_state - Choose the preferred power state of a PCI device
> > + * @dev: PCI device to be put into the low power state
> > + * @sp: Information aboutabout what the driver would prefer to do with
> > + *	the device if there were no platform-implemeted policy.
> > + *
> > + * Returns PCI power state suitable for given device and given suspend policy.
> > + * The policy, however, is only used if platform_pci_choose_state() fails or is
> > + * not present.  Otherwise, it is assumed that platform_pci_choose_state()
> > + * implements the right policy.
> > + */
> > +
> > +pci_power_t pci_preferred_state(struct pci_dev *dev, enum suspend_policy sp)
> > +{
> > +	pci_power_t ret;
> > +
> > +	if (!pci_find_capability(dev, PCI_CAP_ID_PM))
> > +		return PCI_D0;
> > +
> > +	ret = (sp == SP_TURN_OFF) ? PCI_D3hot : PCI_D0;
> > +	if (platform_pci_choose_state) {
> > +		pci_power_t platform_ret = platform_pci_choose_state(dev);
> > +
> > +		if (platform_ret != PCI_POWER_ERROR)
> > +			ret = platform_ret;
> > +	}
> > +	return ret;
> > +}
> > +
> > +EXPORT_SYMBOL(pci_preferred_state);
> 
> I don't get it. How is driver supposed to use this? How does the
> driver decide between SP_TURN_OFF and SP_TURN_ON?
> 
> ...and it seems to be clearer to just inline this in the driver... or
> pass  PCI_D3hot/PCI_D0 to it, instead of inventing yet another
> define...

I thought about that too.  I'd like to know what the other people think,
though.

Thanks,
Rafael