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? > 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. > In our box, when the device is not present and not functional, _SUN method > of the device returns wrong value. And the values is cached to > acpi_device->pnp.sun. So when hot adding the device and changing _SUN value, > the information is not reflected to acpi_device->pnp.sun. I see. > I think the issue is solved by not caching sun value. But at first, I want > to know whether current implementation is correct or not. No, it isn't, but there are two ways to fix it. A short term fix would be to evaluate _STA and print an empty string in acpi_device_sun_show() if we don't like the return value. If we do like it, evaluate _SUN and print the result. A long term fix would require us to track the execution of _INI and decide what to print on this basis (and probably avoid to execute some other methods too if _INI has not been executed). I'll try to do something along these lines, but I can't promise any particular time frame, sorry about that. KR, Rafael -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center. -- 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
