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Diffstat (limited to 'Documentation/firmware-guide/acpi/enumeration.rst')
| -rw-r--r-- | Documentation/firmware-guide/acpi/enumeration.rst | 39 |
1 files changed, 36 insertions, 3 deletions
diff --git a/Documentation/firmware-guide/acpi/enumeration.rst b/Documentation/firmware-guide/acpi/enumeration.rst index 9f0d5c854fa4..74b830b2fd59 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> + 600000000, // <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 ms (note that +value is given in nanoseconds). + GPIO support ============ @@ -339,8 +371,8 @@ a code like this:: There are also devm_* versions of these functions which release the descriptors once the device is released. -See Documentation/firmware-guide/acpi/gpio-properties.rst for more information about the -_DSD binding related to GPIOs. +See Documentation/firmware-guide/acpi/gpio-properties.rst for more information +about the _DSD binding related to GPIOs. MFD devices =========== @@ -460,7 +492,8 @@ the _DSD of the device object itself or the _DSD of its ancestor in the Otherwise, the _DSD itself is regarded as invalid and therefore the "compatible" property returned by it is meaningless. -Refer to :doc:`DSD-properties-rules` for more information. +Refer to Documentation/firmware-guide/acpi/DSD-properties-rules.rst for more +information. PCI hierarchy representation ============================ |