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SubjectRe: Solving suspend-level confusion
Hi!

> > > So suspend-to-RAM more or less matches PCI D3hot, and
> > > suspend-to-DISK matches PCI D3cold. If those power states
> > > were passed to the device suspend(), the disk driver could act
> > > appropriately. In my observation, D3cold was never passed
> > > down, it was always D3hot.
> >
> > Not really, they really have nothing to do with the PCI state
> > at all.
>
> The PCI power state is rather fundamental to what PCI suspend()
> does! Even if you want to redefine the "u32 state" parameter
> to be something that's first got to be mapped _into_ a PCI
> power state before calling pci_set_power_state().

For example harddrive wants to be in D0 during reboot. Now imagine
that BIOS can't handle soundcard in D0 during reboot (I believe some
such examples exists).... You only have D0, D1, D2, D3hot, D3cold; but
low-level driver really needs more info.
Now, you could have quirks at PCI layer saying "this device needs to
be D3 during reboot", but I believe thats ugly.

I believe right solution is to pass system state into suspend(), and
provide system_to_pci_state(), so that drivers that only care about
PCI state can use.

If you are right, every PCI driver will use system_to_pci_state.. but
I do not think that's the case. For example:

static void ide_device_shutdown(struct device *dev)
{
ide_drive_t *drive = container_of(dev, ide_drive_t, gendev);
#ifdef CONFIG_ALPHA
/* On Alpha, halt(8) doesn't actually turn the machine off,
it puts you into the sort of firmware monitor. Typically,
it's used to boot another kernel image, so it's not much
different from reboot(8). Therefore, we don't need to
spin down the disk in this case, especially since Alpha
firmware doesn't handle disks in standby mode properly.
On the other hand, it's reasonably safe to turn the power
off when the shutdown process reaches the firmware prompt,
as the firmware initialization takes rather long time -
at least 10 seconds, which should be sufficient for
the disk to expire its write cache. */
if (system_state != SYSTEM_POWER_OFF) {
#else
if (system_state == SYSTEM_RESTART) {
#endif
...drivers are weird. Please provide them with full information.

Pavel
--
People were complaining that M$ turns users into beta-testers...
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