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Add a simple, generic, single register fixed-direction GPIO driver.
This is able to support a single register with a mixture of inputs
and outputs.
This is different from gpio-mmio and gpio-74xx-mmio:
* gpio-mmio doesn't allow a fixed direction, it assumes there is always
a direction register.
* gpio-74xx-mmio only supports all-in or all-out setups
* gpio-74xx-mmio is DT only, this needs to support legacy too
* they don't double-read when getting the GPIO value, as required by
some implementations that this driver supports
* we need to always do 32-bit reads, which bgpio doesn't guarantee
* the current output state may not be readable from the hardware
register - reading may reflect input status but not output status.
Signed-off-by: Russell King <[email protected]>
Signed-off-by: Linus Walleij <[email protected]>
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