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Date: Wed, 18 Mar 2015 13:16:22 -0700
From: David Cohen <david.a.cohen@...ux.intel.com>
To: linus.walleij@...aro.org, gnurou@...il.com
Cc: linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
David Cohen <david.a.cohen@...ux.intel.com>
Subject: [RFC] gpio: add set_active_low() function to gpio_chip
Some gpio controllers are capable of programming its pins' active-low
state. Let's add this new gpio_chip function for such cases and use it
in gpiolib.
When set_active_low() is implemented, we no longer need to do soft flips
on values from non-raw get functions.
Signed-off-by: David Cohen <david.a.cohen@...ux.intel.com>
---
Hi,
This is a RFC, not meant for integration (yet).
We have a GPIO controller that is capable of inverting the GPIO logical value
on hardware using a register (and GPIO voltage level if configured for output):
- If GPIO pin is configured for input, only the logical value is affected: the
GPIO level stays the same but the read values are inverted (it affects even
interrupt event triggers).
- If GPIO pin is configured for output, the GPIO level is also inverted.
Is it acceptable to expose this functionality via new gpio chip operation
set_active_low()?
Comments are welcome.
Br, David
---
drivers/gpio/gpiolib-sysfs.c | 4 ++++
drivers/gpio/gpiolib.c | 6 ++++--
include/linux/gpio/driver.h | 2 ++
3 files changed, 10 insertions(+), 2 deletions(-)
diff --git a/drivers/gpio/gpiolib-sysfs.c b/drivers/gpio/gpiolib-sysfs.c
index 7722ed53bd65..316a1d008cad 100644
--- a/drivers/gpio/gpiolib-sysfs.c
+++ b/drivers/gpio/gpiolib-sysfs.c
@@ -289,11 +289,15 @@ static DEVICE_ATTR(edge, 0644, gpio_edge_show, gpio_edge_store);
static int sysfs_set_active_low(struct gpio_desc *desc, struct device *dev,
int value)
{
+ struct gpio_chip *chip = desc->chip;
int status = 0;
if (!!test_bit(FLAG_ACTIVE_LOW, &desc->flags) == !!value)
return 0;
+ if (chip->set_active_low)
+ chip->set_active_low(chip, gpio_chip_hwgpio(desc), value);
+
if (value)
set_bit(FLAG_ACTIVE_LOW, &desc->flags);
else
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 1ca9295b2c10..028a0d34ddab 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -1196,7 +1196,8 @@ int gpiod_get_value(const struct gpio_desc *desc)
WARN_ON(desc->chip->can_sleep);
value = _gpiod_get_raw_value(desc);
- if (test_bit(FLAG_ACTIVE_LOW, &desc->flags))
+ if (!desc->chip->set_active_low &&
+ test_bit(FLAG_ACTIVE_LOW, &desc->flags))
value = !value;
return value;
@@ -1550,7 +1551,8 @@ int gpiod_get_value_cansleep(const struct gpio_desc *desc)
return 0;
value = _gpiod_get_raw_value(desc);
- if (test_bit(FLAG_ACTIVE_LOW, &desc->flags))
+ if (!desc->chip->set_active_low &&
+ test_bit(FLAG_ACTIVE_LOW, &desc->flags))
value = !value;
return value;
diff --git a/include/linux/gpio/driver.h b/include/linux/gpio/driver.h
index c497c62889d1..2d665352fd69 100644
--- a/include/linux/gpio/driver.h
+++ b/include/linux/gpio/driver.h
@@ -90,6 +90,8 @@ struct gpio_chip {
unsigned offset);
void (*set)(struct gpio_chip *chip,
unsigned offset, int value);
+ void (*set_active_low)(struct gpio_chip *chip,
+ unsigned offset, int value);
void (*set_multiple)(struct gpio_chip *chip,
unsigned long *mask,
unsigned long *bits);
--
2.1.4
--
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