On Wednesday 16 January 2008 18:46:03 Bjorn Helgaas wrote: > On Tuesday 15 January 2008 12:51:35 am Jaroslav Kysela wrote: > > On Mon, 14 Jan 2008, Bjorn Helgaas wrote: > > > On Saturday 12 January 2008 11:13:35 pm Rene Herman wrote: > > > > ... And, now that I have your attention, while it's > > > > not important to the issue anymore with the tests removed as the > > > > submitted patch did, do you have an opinion on (include/linux/pnp.h): > > > > > > > > /* pnp driver flags */ > > > > #define PNP_DRIVER_RES_DO_NOT_CHANGE 0x0001 /* do not change the > > > > state of the device */ > > > > #define PNP_DRIVER_RES_DISABLE 0x0003 /* ensure the device > > > > is disabled */ > > > > > > > > I find DISABLE including DO_NOT_CHANGE rather unexpected... > > > > > > I don't know the history of those flags, but I wish they didn't exist. > > > > Ok, something to explain. These flags exists to allow drivers to > > manually configure (override) PnP resources at init time - we know - for > > example in ALSA - that some combinations simply does not work for all > > soundcards. > > > > The DISABLE flags simply tells core PnP layer - driver will handle > > resource allocation itself, don't do anything, just disable hw physically > > and do not change (allocate) any resources. Value 0x03 is valid in this > > semantics. > > It looks like sound drivers use PNP_DRIVER_RES_DISABLE to say "ignore > what PNP tells us about resource usage and we'll just use the compiled- > in or command-line-specified resources". > > The main reason to do that would be to work around BIOS defects or > to work around deficiencies in the Linux PNP infrastructure (e.g., > maybe we erroneously place another device on top of the sound card > or something). > > I'm just suspicious because PNP_DRIVER_RES_DISABLE is only used in > sound drivers. If it's to work around BIOS defects, why wouldn't > other PNP drivers need it sometimes, too? And wouldn't it be better > to use PNP quirks for BIOS workarounds? > > > Unfortunately, suspend / resume complicates things a bit, but PnP core > > can handle DO_NOT_CHANGE flag. But it will just mean - _preserve_ > > resource allocation from last suspend state for this device and enable hw > > physically before calling resume() callback. > > When resuming, wouldn't we *always* want to preserve the resource > allocation from the last suspend, regardless of whether > PNP_DRIVER_RES_DO_NOT_CHANGE is specified? I'd say yes. If base address of a card changes, driver will break. I grepped drivers for these flags too - to find out what they do (or should do?) - but failed to find out anything useful. > Linux PNP definitely has issues with suspend/resume, and I suspect > this is one of them. > > Bjorn > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- Ondrej Zary _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
