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gpio: Add support for GPIOF_ACTIVE_LOW to gpio_request_one functions

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The gpio include file and the gpio documentation declare and document
GPIOF_ACTIVE_LOW as one of the flags to be passed to gpio_request_one
and related functions. However, the flag is not evaluated or used.

This can cause problems in at least two areas: First, the same API can
be used to auto-export pins to user space. The missing support for
GPIOF_ACTIVE_LOW results in unexpected behavior for such auto-exported
pins. Second, the requested gpio pin can be convered for use by
gpiod functions with gpio_to_desc(). While gpio API functions do not
support GPIOF_ACTIVE_LOW, gpiod functions do, which again results in
unexpected behavior.

Check the flag in gpio_request_one and set the gpio internal flag
FLAG_ACTIVE_LOW if it is set to address those problems.

Signed-off-by: Guenter Roeck <[email protected]>
Reviewed-by: Alexandre Courbot <[email protected]>
Signed-off-by: Linus Walleij <[email protected]>
This commit is contained in:
Guenter Roeck 2014-07-21 11:12:16 -07:00 • committed by Linus Walleij
commit 2be0017392
1 changed files with 3 additions and 0 deletions
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3
drivers/gpio/gpiolib-legacy.c
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@ -34,6 +34,9 @@ int gpio_request_one(unsigned gpio, unsigned long flags, const char *label)
if (flags & GPIOF_OPEN_SOURCE)
set_bit(FLAG_OPEN_SOURCE, &desc->flags);
if (flags & GPIOF_ACTIVE_LOW)
set_bit(FLAG_ACTIVE_LOW, &desc->flags);
if (flags & GPIOF_DIR_IN)
err = gpiod_direction_input(desc);
else