linux-kernel - [PATCH v4 2/3] docs: firmware-guide: ACPI: Add named interrupt doc

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Date:   Sat, 22 Jan 2022 17:02:45 +0530
From:   Akhil R <akhilrajeev@...dia.com>
To:     <u.kleine-koenig@...gutronix.de>, <andy.shevchenko@...il.com>,
        <christian.koenig@....com>, <digetx@...il.com>,
        <gregkh@...uxfoundation.org>, <jonathanh@...dia.com>,
        <ldewangan@...dia.com>, <lenb@...nel.org>,
        <linux-acpi@...r.kernel.org>, <linux-i2c@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-tegra@...r.kernel.org>,
        <rafael@...nel.org>, <sumit.semwal@...aro.org>,
        <thierry.reding@...il.com>, <wsa@...nel.org>
CC:     <akhilrajeev@...dia.com>
Subject: [PATCH v4 2/3] docs: firmware-guide: ACPI: Add named interrupt doc

Add a detailed example of the named interrupts in the ACPI table.

Signed-off-by: Akhil R <akhilrajeev@...dia.com>
---
 Documentation/firmware-guide/acpi/enumeration.rst | 39 +++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/Documentation/firmware-guide/acpi/enumeration.rst b/Documentation/firmware-guide/acpi/enumeration.rst
index 74b830b2..d002256 100644
--- a/Documentation/firmware-guide/acpi/enumeration.rst
+++ b/Documentation/firmware-guide/acpi/enumeration.rst
@@ -143,6 +143,45 @@ In robust cases the client unfortunately needs to call
 acpi_dma_request_slave_chan_by_index() directly and therefore choose the
 specific FixedDMA resource by its index.
 
+Named Interrupts
+================
+
+Drivers enumerated via ACPI can have names to interrupts in the ACPI table
+which can be used to get the IRQ number in the driver.
+
+The interrupt name can be listed in _DSD as 'interrupt-names'. The names
+should be listed as an array of strings which will map to the Interrupt()
+resource in the ACPI table corresponding to its index.
+
+The table below shows an example of its usage::
+
+    Device (DEV0) {
+        ...
+        Name (_CRS, ResourceTemplate() {
+            ...
+            Interrupt (ResourceConsumer, Level, ActiveHigh, Exclusive) {
+                0x20,
+                0x24
+            }
+        })
+
+        Name (_DSD, Package () {
+            ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
+            Package () {
+                Package () {"interrupt-names",
+                Package (2) {"default", "alert"}},
+            }
+        ...
+        })
+    }
+
+The interrupt name 'default' will correspond to 0x20 in Interrupt()
+resource and 'alert' to 0x24. Note that only the Interrupt() resource
+is mapped and not GpioInt() or similar.
+
+The driver can call the function - fwnode_irq_get_byname() with the fwnode
+and interrupt name as arguments to get the corresponding IRQ number.
+
 SPI serial bus support
 ======================
 
-- 
2.7.4