Hi Simon,
-----"Simon Glass" sjg@chromium.org schrieb: ----- Hi Wolfgang,
On Fri, 31 Jan 2020 at 01:18, Wolfgang Wallner wolfgang.wallner@br-automation.com wrote:
Hi Simon,
+Devices +=======
+Device bindings are described by their own individual binding files.
+U-Boot provides for some optional properties which are documented here.
- acpi,has-power-resource : (boolean) true if this device has a power resource.
- This causes a PRIC (ACPI PowerResource) to be written containing the
- properties provided by this binding, to describe how to handle powering the
- device up and down using GPIOs
- acpi,cid : Contains the string to use as the compatible ID (_CID)
- acpi,compatible : compatible string to report
- acpi,desc : Contains the string to use as the _DDN (DOS (Disk Operating
- System) Device Name)
- acpi,hid : Contains the string to use as the HID (Human Interface Device)
- identifier _HID
Nit: "_HID" in ACPI stands for "Hardware ID"
OK thank you, will fix. I am trying to write things out in full since it is very hard to find out what all these different things mean.
I appreciate that, it makes it easier for to follow the text.
- acpi,hid-desc-reg-offset : HID register offset (for Human Interface Devices)
- acpi,probed : Tells U-Boot to add 'linux,probed' to the ACPI tables so that
- Linux will not re-init the device
- acpi,uid : _UID value for device
Would it make sense to automatically infer ACPI properties from existing device tree properties?
E.g. if the compatible string contains "hid-over-i2c", then _CID could be set to "PNP0C50".
Yes we could do that. So is that true for all devices that use this i2c driver?
As far as I understand the ids "PNP0C50" and "hid-over-i2c" serve the same purpose, just in two different description languages.
Devicetree: If an I2C over HID device is described in Devicetree, it should have a compatible string of "hid-over-i2c" (see [1] for details).
ACPI: If an I2C over HID device is described in ACPI, it should have a _CID of "PNP0C50" (See [2] for details).
[1] https://github.com/torvalds/linux/blob/master/Documentation/devicetree/bindi... [2] https://docs.microsoft.com/en-us/windows-hardware/drivers/hid/plug-and-play-...
As both identifiers are standardized, I think we could infer one from the other.
I'm not sure whether inferring ACPI-properties from Devicetree properties is worth it, but I wanted to bring up the idea for discussion as adding new properties for someting where we already have something similar feels redundant.
And a "hid-over-i2c" device would also have a "hid-descr-addr" device tree property for the offset of the HID descriptor register which could be passed on in ACPI as part of the _DSM method.
Are you suggesting renaming acpi,hid-desc-reg-offset to hid-descr-addr?
An ACPI "PNP0C50"-device has a _DSM (Device Specific Method) which provides the HID descriptor offset (for UUID "3CDFF6F7-4267-4555-AD05-B30A3D8938DE").
A Devicetree "hid-over-i2c"-device has a property "hid-descr-addr" which provides the HID descriptor offset.
So instead of adding a new "acpi,hid-desc-reg-offset" I think we could also use the existing "hid-descr-addr" property.
Interrupts are another topic that need to be described in both worlds:
Devicetree: "interrupts"-property ACPI: "_CRS"-method (Current Resource Settings)
Maybe we could also infer that description too?
regards, Wolfgang