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From:   Thomas Preston <thomas.preston@codethink.co.uk>
To:     rjw@rjwysocki.net, lenb@kernel.org, linux-acpi@vger.kernel.org,
        linux-kernel@vger.kernel.org, andriy.shevchenko@linux.intel.com,
        mika.westerberg@linux.intel.com
Cc:     Thomas Preston <thomas.preston@codethink.co.uk>
Subject: [PATCH v2] Documentation: acpi: Add an example for PRP0001
Date:   Mon, 25 Mar 2019 15:12:10 +0000
Message-Id: <20190325151210.23226-1-thomas.preston@codethink.co.uk>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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.

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")
+
+		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
-- 
2.11.0