diff options
Diffstat (limited to 'Documentation/acpi/enumeration.txt')
| -rw-r--r-- | Documentation/acpi/enumeration.txt | 42 |
1 files changed, 7 insertions, 35 deletions
diff --git a/Documentation/acpi/enumeration.txt b/Documentation/acpi/enumeration.txt index b994bcb32b9..e182be5e3c8 100644 --- a/Documentation/acpi/enumeration.txt +++ b/Documentation/acpi/enumeration.txt @@ -60,12 +60,6 @@ If the driver needs to perform more complex initialization like getting and configuring GPIOs it can get its ACPI handle and extract this information from ACPI tables. -Currently the kernel is not able to automatically determine from which ACPI -device it should make the corresponding platform device so we need to add -the ACPI device explicitly to acpi_platform_device_ids list defined in -drivers/acpi/acpi_platform.c. This limitation is only for the platform -devices, SPI and I2C devices are created automatically as described below. - DMA support ~~~~~~~~~~~ DMA controllers enumerated via ACPI should be registered in the system to @@ -293,36 +287,13 @@ the device to the driver. For example: These GPIO numbers are controller relative and path "\\_SB.PCI0.GPI0" specifies the path to the controller. In order to use these GPIOs in Linux -we need to translate them to the Linux GPIO numbers. - -In a simple case of just getting the Linux GPIO number from device -resources one can use acpi_get_gpio_by_index() helper function. It takes -pointer to the device and index of the GpioIo/GpioInt descriptor in the -device resources list. For example: - - int gpio_irq, gpio_power; - int ret; - - gpio_irq = acpi_get_gpio_by_index(dev, 1, NULL); - if (gpio_irq < 0) - /* handle error */ - - gpio_power = acpi_get_gpio_by_index(dev, 0, NULL); - if (gpio_power < 0) - /* handle error */ - - /* Now we can use the GPIO numbers */ - -Other GpioIo parameters must be converted first by the driver to be -suitable to the gpiolib before passing them. +we need to translate them to the corresponding Linux GPIO descriptors. -In case of GpioInt resource an additional call to gpio_to_irq() must be -done before calling request_irq(). +There is a standard GPIO API for that and is documented in +Documentation/gpio/. -Note that the above API is ACPI specific and not recommended for drivers -that need to support non-ACPI systems. The recommended way is to use -the descriptor based GPIO interfaces. The above example looks like this -when converted to the GPIO desc: +In the above example we can get the corresponding two GPIO descriptors with +a code like this: #include <linux/gpio/consumer.h> ... @@ -339,4 +310,5 @@ when converted to the GPIO desc: /* Now we can use the GPIO descriptors */ -See also Documentation/gpio.txt. +There are also devm_* versions of these functions which release the +descriptors once the device is released. |