Messages in this thread Patch in this message | | | Subject | Re: [PATCH v2] Documentation: acpi: Add an example for PRP0001 | From | Thomas Preston <> | Date | Mon, 25 Mar 2019 15:58:13 +0000 |
| |
On 25/03/2019 15:30, Andy Shevchenko wrote: > On Mon, Mar 25, 2019 at 03:12:10PM +0000, Thomas Preston wrote: >> Add an example for the magic PRP0001 device ID which allows matching >> ACPI devices against drivers using OF Device Tree compatible property. > >> It wasn't clear to me that PRP0001 could be used in _CID. > > Yes, but it's not necessary to have it if we have defined a _HID. > > In that case PRP0001 is a temporary stub until corresponding driver > incorporates an official _HID. > > On the contrary, when there is no official _HID available, PRP0001 can be used > instead directly as a _HID and no _CID is needed. >
In that case, how do we uniquely identify devices in sysfs? We have a case where sound/soc/soc-core.c generates an i2c codec name i2c-TDA7802:00. It is useful to identify that device by part name, rather than some indexed generic PRP device i2c-PRP0001:04. I can achieve this with:
_HID("TDA7802") _CID("PRP0001") ... compatible = "st,tda7802" // driver I want to load using OF DT
> I would really recommend to look at the examples in meta-acpi repository. There > are cases like described above. > > This one is good enough, though see below. >
I will drop the superfluous _CID - I think the example is still useful to have. Even if we don't illustrate my special case for _HID/_CID.
>> Signed-off-by: Thomas Preston <thomas.preston@codethink.co.uk> >> --- >> Documentation/acpi/enumeration.txt | 31 +++++++++++++++++++++++++++++++ >> 1 file changed, 31 insertions(+) >> >> diff --git a/Documentation/acpi/enumeration.txt b/Documentation/acpi/enumeration.txt >> index 7bcf9c3d9fbe..8375fc506b47 100644 >> --- a/Documentation/acpi/enumeration.txt >> +++ b/Documentation/acpi/enumeration.txt >> @@ -410,6 +410,37 @@ Specifically, the device IDs returned by _HID and preceding PRP0001 in the _CID >> return package will be checked first. Also in that case the bus type the device >> will be enumerated to depends on the device ID returned by _HID. >> >> +For example, the following ACPI sample might be used to enumerate an lm75-type >> +I2C temperature sensor and match it to the driver using the Device Tree >> +namespace link: >> + >> + Device (TMP0) >> + { >> + /* _HID will appear in sysfs */ >> + Name (_HID, "PRP0001") >> + > >> + /* _CID can also be used to search for "compatible" property */ >> + Name (_CID, "PRP0001") > > So, these lines are superfluous as stated exaxtly in a following paragraph. > >> + >> + Name (_DSD, Package() { >> + ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"), >> + Package () { >> + Package (2) { "compatible", "ti,tmp75" }, >> + } >> + }) >> + Method (_CRS, 0, Serialized) >> + { >> + Name (SBUF, ResourceTemplate () >> + { >> + I2cSerialBusV2 (0x48, ControllerInitiated, >> + 400000, AddressingMode7Bit, >> + "\\_SB.PCI0.I2C1", 0x00, >> + ResourceConsumer, , Exclusive,) >> + }) >> + Return (SBUF) >> + } >> + } >> + >> It is valid to define device objects with a _HID returning PRP0001 and without >> the "compatible" property in the _DSD or a _CID as long as one of their >> ancestors provides a _DSD with a valid "compatible" property. Such device >
| |