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Diffstat (limited to 'Documentation/driver-api/gpio/board.rst')
| -rw-r--r-- | Documentation/driver-api/gpio/board.rst | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/Documentation/driver-api/gpio/board.rst b/Documentation/driver-api/gpio/board.rst index 2c112553df84..c66821e033c2 100644 --- a/Documentation/driver-api/gpio/board.rst +++ b/Documentation/driver-api/gpio/board.rst @@ -193,3 +193,18 @@ And the table can be added to the board code as follows:: The line will be hogged as soon as the gpiochip is created or - in case the chip was created earlier - when the hog table is registered. + +Arrays of pins +-------------- +In addition to requesting pins belonging to a function one by one, a device may +also request an array of pins assigned to the function. The way those pins are +mapped to the device determines if the array qualifies for fast bitmap +processing. If yes, a bitmap is passed over get/set array functions directly +between a caller and a respective .get/set_multiple() callback of a GPIO chip. + +In order to qualify for fast bitmap processing, the pin mapping must meet the +following requirements: +- it must belong to the same chip as other 'fast' pins of the function, +- its index within the function must match its hardware number within the chip. + +Open drain and open source pins are excluded from fast bitmap output processing. |