On Wednesday, September 03, 2014 11:14:02 AM Yasuaki Ishimatsu wrote: > Hi Rafael, Hi, > Thank you for your explanation. > > (2014/09/03 6:29), Rafael J. Wysocki wrote: > > On Tuesday, September 02, 2014 10:53:09 AM Yasuaki Ishimatsu wrote: > >> Hi Rafael, > > > > Hi, > > > >> Why is _SUN method decoded and the sun sysfs created even if _STA reports > >> that the device is not present and not functional? > > > > sun sysfs is created for stuff that has _SUN. It should be empty for devices > > that aren't present, though, apparently. > > > >> By this commit, "202317a : ACPI / scan: Add acpi_device objects for all > >> device nodes in the namespace", all device nodes in the namespace are > >> shown under /sys/bus/acpi/devices direcotry even if the devices are not > >> present and not functional. > >> > >> But ACPI specification says against return value information of _STA: > >> A device can only decode its hardware resources if both bits 0 and 1 are set. > >> If the device is not present (bit 0 cleared) or not enabled (bit 1 cleared), > >> then the device must not decode its resources. > > > > But _SUN is not about hardware resources, is it? > > I think so. But ACPI spec does not define what the hardware resources are. > So someone says _SUN is about hardware resrouces. Well, that is a very far fetched interpretation that I can't see any kind of support for in the spec or elsewhere. Nevertheless, it is not required that the return value of _SUN be the same every time it is evaluated, so caching it is questionable. > > > >> In my understanding, when the device is not present and not functional, > >> _SUN of the device must not be decoded. Is my understanding worng? > > > > If my understanding of the _INI section of the spec is correct, you have a > > point, but the dependency is rather indirect as far as I can say. If the > > device is not present, we are not supposed to execute _INI for it and _SUN > > can only be executed after _INI. > > I know the spec. According to the _INI section of the spec, it says: > > "If the _STA method indicates that the device is not present and is not > functional, OSPM will not run the _INI and will not examine the children > of the device for _INI methods." > > In my understanding, if a device has both _SUN and _INI method, and _STA > method indicates that the deviceis not present and is not functional, > _SUN method cannot be executed. > > If a device has _SUN method and does not have _INI method, and _STA > method indicates that the deviceis not present and is not functional, > can we execute _SUN method? I'd think so. I don't see anything preventing us from doing that in the spec. Rafael -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
