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Diffstat (limited to 'Documentation/gpio.txt')
| -rw-r--r-- | Documentation/gpio.txt | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/Documentation/gpio.txt b/Documentation/gpio.txt index 54630095aa3..c35ca9e40d4 100644 --- a/Documentation/gpio.txt +++ b/Documentation/gpio.txt @@ -107,6 +107,16 @@ type of GPIO controller, and on one particular board 80-95 with an FPGA. The numbers need not be contiguous; either of those platforms could also use numbers 2000-2063 to identify GPIOs in a bank of I2C GPIO expanders. +If you want to initialize a structure with an invalid GPIO number, use +some negative number (perhaps "-EINVAL"); that will never be valid. To +test if a number could reference a GPIO, you may use this predicate: + + int gpio_is_valid(int number); + +A number that's not valid will be rejected by calls which may request +or free GPIOs (see below). Other numbers may also be rejected; for +example, a number might be valid but unused on a given board. + Whether a platform supports multiple GPIO controllers is currently a platform-specific implementation issue. |