On Thu, 16 Jan 2020 19:56:19 +0800 Guoheyi <guoh...@huawei.com> wrote:
> 在 2020/1/5 20:53, Michael S. Tsirkin 写道: > > On Sun, Jan 05, 2020 at 07:34:01AM -0500, Michael S. Tsirkin wrote: > >> On Thu, Dec 19, 2019 at 02:47:59PM +0800, Heyi Guo wrote: > >>> According to ACPI spec, _ADR should be used for device which is on a > >>> bus that has a standard enumeration algorithm. It does not make sense > >>> to have a _ADR object for devices which already have _HID and will be > >>> enumerated by OSPM. > >>> > >>> Signed-off-by: Heyi Guo <guoh...@huawei.com> > >> Are you sure? I would think this depends on the ID and the device > >> really. E.g. PCI devices all are expected to have _ADR and some of them > >> have a _HID. > > > > To clarify I am not commenting on patches. > > The spec says this: > > 6.1.5 _HID (Hardware ID) > > > > This object is used to supply OSPM with the device’s PNP ID or ACPI ID. > > 1 > > > > When describing a platform, use of any _HID objects is optional. > > However, a _HID object must be > > > > used to describe any device that will be enumerated by OSPM. OSPM only > > enumerates a device > > > > when no bus enumerator can detect the device ID. For example, devices > > on an ISA bus are > > > > enumerated by OSPM. Use the _ADR object to describe devices enumerated > > by bus enumerators > > > > other than OSPM. > > > > > > Note: "detect the device ID" not "enumerate the device" which I think > > means there's a driver matching this vendor/device ID. > > > > So it seems fine to have _ADR so device is enumerated, and still have > > _HID e.g. so ACPI driver can be loaded as fallback if there's > > no bus driver. > > > > > > Note I am not saying the patch itself is not correct. > > Maybe these devices are not on any standard bus and that > > is why they should not have _ADR? I have not looked. > > > > I am just saying that spec does not seem to imply _HID and _ADR > > can't coexist. > > More reading on the spec, I found a statement as below > (https://uefi.org/sites/default/files/resources/ACPI_6_3_May16.pdf, > section 6.1, on top of page 343): I'd replace 'It does not make sense ...' sentence with pointer to spec and quote below in commit message. > A device object must contain either an _HID object or an _ADR object, > but should not contain both [...]