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Subject[RFC] gpiolib: Fix gpio_direction_* for single direction GPIOs
Date
GPIOs with no programmable direction are not required to implement
direction_output nor direction_input.

If we try to set an output direction on an output-only GPIO or input
direction on an input-only GPIO simply return 0.

This allows this single direction GPIO to be used by libgpiod.

Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
---
drivers/gpio/gpiolib.c | 36 ++++++++++++++++++++++++++++--------
1 file changed, 28 insertions(+), 8 deletions(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index af853749e0bb..3c09bf70e7ab 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -2517,19 +2517,27 @@ EXPORT_SYMBOL_GPL(gpiochip_free_own_desc);
int gpiod_direction_input(struct gpio_desc *desc)
{
struct gpio_chip *chip;
- int status = -EINVAL;
+ int status = 0;

VALIDATE_DESC(desc);
chip = desc->gdev->chip;

- if (!chip->get || !chip->direction_input) {
+ if (!chip->get && chip->direction_input) {
gpiod_warn(desc,
- "%s: missing get() or direction_input() operations\n",
+ "%s: missing get() and direction_input() operations\n",
__func__);
return -EIO;
}

- status = chip->direction_input(chip, gpio_chip_hwgpio(desc));
+ if (chip->direction_input) {
+ status = chip->direction_input(chip, gpio_chip_hwgpio(desc));
+ } else if (chip->get_direction &&
+ (chip->get_direction(chip, gpio_chip_hwgpio(desc)) != 1)) {
+ gpiod_warn(desc,
+ "%s: missing direction_input() operation\n",
+ __func__);
+ return -EIO;
+ }
if (status == 0)
clear_bit(FLAG_IS_OUT, &desc->flags);

@@ -2551,16 +2559,28 @@ static int gpiod_direction_output_raw_commit(struct gpio_desc *desc, int value)
{
struct gpio_chip *gc = desc->gdev->chip;
int val = !!value;
- int ret;
+ int ret = 0;

- if (!gc->set || !gc->direction_output) {
+ if (!gc->set && !gc->direction_output) {
gpiod_warn(desc,
- "%s: missing set() or direction_output() operations\n",
+ "%s: missing set() and direction_output() operations\n",
__func__);
return -EIO;
}

- ret = gc->direction_output(gc, gpio_chip_hwgpio(desc), val);
+ if (gc->direction_output) {
+ ret = gc->direction_output(gc, gpio_chip_hwgpio(desc), val);
+ } else {
+ if (gc->get_direction &&
+ gc->get_direction(gc, gpio_chip_hwgpio(desc))) {
+ gpiod_warn(desc,
+ "%s: missing direction_output() operation\n",
+ __func__);
+ return -EIO;
+ }
+ gc->set(gc, gpio_chip_hwgpio(desc), val);
+ }
+
if (!ret)
set_bit(FLAG_IS_OUT, &desc->flags);
trace_gpio_value(desc_to_gpio(desc), 0, val);
--
2.18.0
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