linux-kernel - [PATCH v1 1/5] docs: firmware-guide: ACPI: Add a PWM example

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <20210531154351.53614-1-andriy.shevchenko@linux.intel.com>
Date:   Mon, 31 May 2021 18:43:47 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Flavio Suligoi <f.suligoi@...m.it>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        Thierry Reding <thierry.reding@...il.com>,
        linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-pwm@...r.kernel.org
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>, Lee Jones <lee.jones@...aro.org>
Subject: [PATCH v1 1/5] docs: firmware-guide: ACPI: Add a PWM example

When PWM support for ACPI has been added into the kernel, it missed
the documentation update. Hence update documentation here.

Fixes: 4a6ef8e37c4d ("pwm: Add support referencing PWMs from ACPI")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
---
 .../firmware-guide/acpi/enumeration.rst       | 32 +++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/Documentation/firmware-guide/acpi/enumeration.rst b/Documentation/firmware-guide/acpi/enumeration.rst
index 9f0d5c854fa4..0813508b45b0 100644
--- a/Documentation/firmware-guide/acpi/enumeration.rst
+++ b/Documentation/firmware-guide/acpi/enumeration.rst
@@ -258,6 +258,38 @@ input driver::
 		.id_table	= mpu3050_ids,
 	};
 
+Reference to PWM device
+=======================
+
+Sometimes a device can be a consumer of PWM channel. Obviously OS would like
+to know which one. To provide this mapping the special property has been
+introduced, i.e.::
+
+    Device (DEV)
+    {
+        Name (_DSD, Package ()
+        {
+            ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
+            Package () {
+                Package () { "compatible", Package () { "pwm-leds" } },
+                Package () { "label", "alarm-led" },
+                Package () { "pwms",
+                    Package () {
+                        "\\_SB.PCI0.PWM",  // <PWM device reference>
+                        0,                 // <PWM index>
+                        600000,            // <PWM period>
+                        0,                 // <PWM flags>
+                    }
+                }
+            }
+
+        })
+        ...
+
+In the above example the PWM-based LED driver references to the PWM channel 0
+of \_SB.PCI0.PWM device with initial period setting equal to 600 us (note that
+value is given in nanoseconds).
+
 GPIO support
 ============
 
-- 
2.30.2