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Diffstat (limited to 'Documentation/acpi/gpio-properties.txt')
| -rw-r--r-- | Documentation/acpi/gpio-properties.txt | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/Documentation/acpi/gpio-properties.txt b/Documentation/acpi/gpio-properties.txt index 5aafe0b351a1..09cff657b82c 100644 --- a/Documentation/acpi/gpio-properties.txt +++ b/Documentation/acpi/gpio-properties.txt @@ -51,6 +51,21 @@ it to 1 marks the GPIO as active low. In our Bluetooth example the "reset-gpios" refers to the second GpioIo() resource, second pin in that resource with the GPIO number of 31. +It is possible to leave holes in the array of GPIOs. This is useful in +cases like with SPI host controllers where some chip selects may be +implemented as GPIOs and some as native signals. For example a SPI host +controller can have chip selects 0 and 2 implemented as GPIOs and 1 as +native: + + Package () { + "cs-gpios", + Package () { + ^GPIO, 19, 0, 0, // chip select 0: GPIO + 0, // chip select 1: native signal + ^GPIO, 20, 0, 0, // chip select 2: GPIO + } + } + ACPI GPIO Mappings Provided by Drivers -------------------------------------- |