gpio: of: make it possible to name GPIO lines

Make it possible to name the producer side of a GPIO line using
a "gpio-line-names" property array, modeled on the
"clock-output-names" property from the clock bindings.

This naming is especially useful for:

- Debugging: lines are named after function, not just opaque
  offset numbers.

- Exploration: systems where some or all GPIO lines are available
  to end users, such as prototyping, one-off's "makerspace usecases"
  users are helped by the names of the GPIO lines when tinkering.
  This usecase has been surfacing recently.

The gpio-line-names attribute is completely optional.

Example output from lsgpio on a patched Snowball tree:

GPIO chip: gpiochip6, "8000e180.gpio", 32 GPIO lines
        line  0: unnamed unused
        line  1: "AP_GPIO161" "extkb3" [kernel]
        line  2: "AP_GPIO162" "extkb4" [kernel]
        line  3: "ACCELEROMETER_INT1_RDY" unused [kernel]
        line  4: "ACCELEROMETER_INT2" unused
        line  5: "MAG_DRDY" unused [kernel]
        line  6: "GYRO_DRDY" unused [kernel]
        line  7: "RSTn_MLC" unused
        line  8: "RSTn_SLC" unused
        line  9: "GYRO_INT" unused
        line 10: "UART_WAKE" unused
        line 11: "GBF_RESET" unused
        line 12: unnamed unused

Cc: Grant Likely <[email protected]>
Cc: Amit Kucheria <[email protected]>
Cc: David Mandala <[email protected]>
Cc: Lee Campbell <[email protected]>
Cc: [email protected]
Acked-by: Rob Herring <[email protected]>
Reviewed-by: Michael Welling <[email protected]>
Signed-off-by: Linus Walleij <[email protected]>

0 files changed, 0 insertions, 0 deletions