Re: [PATCH v2 13/39] acpi: Add a binding for ACPI settings in the device tree

On Sun, Mar 08, 2020 at 09:44:37PM -0600, Simon Glass wrote:

Devices need to report various identifiers in the ACPI tables. Rather than hard-coding these in drivers it is typically better to put them in the device tree.

Add a binding file to describe this.

...

+Device bindings are described by their own individual binding files.

+U-Boot provides for some optional properties which are documented here. See +also hid-over-i2c.txt which describes HID devices.

• • acpi,has-power-resource : (boolean) true if this device has a power resource.
• This causes a PRIC (ACPI PowerResource) to be written containing the

What is PRIC?

• properties provided by this binding, to describe how to handle powering the
• device up and down using GPIOs

• • acpi,compatible : compatible string to report

Hmm... I didn't get this. Is it ACPI _CID?

• • 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 (Hardware ID)
• identifier _HID

HID can be dropped to avoid confusion with below.

• • hid-descr-addr : 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

Why? How do we know that Linux will work correctly? Again, we must not depend on the OS behaviour.

• • acpi,uid : _UID value for device

+Example +-------

+synaptics_touchpad: synaptics-touchpad@2c {

• compatible = "hid-over-i2c";
• reg = <0x2c>;
• acpi,hid = "PNP0C50";
• acpi,desc = "Synaptics Touchpad";
• interrupts-extended = <&acpi_gpe GPIO_18_IRQ

• 	IRQ_TYPE_EDGE_FALLING>;
  

• acpi,probed;
• hid-descr-addr = <0x20>;

+};