gpio: gpio_{request,free}() now required (feature removal)
We want to phase out the GPIO "autorequest" mechanism in gpiolib and
require all callers to use gpio_request().
- Update feature-removal-schedule
- Update the documentation now
- Convert the relevant pr_warning() in gpiolib to a WARN()
so folk using this mechanism get a noisy stack dump
Some drivers and board init code will probably need to change.
Implementations not using gpiolib will still be fine; they are already
required to implement gpio_{request,free}() stubs.
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/Documentation/feature-removal-schedule.txt b/Documentation/feature-removal-schedule.txt
index d0f3546..a23361e 100644
--- a/Documentation/feature-removal-schedule.txt
+++ b/Documentation/feature-removal-schedule.txt
@@ -255,6 +255,16 @@
---------------------------
+What: GPIO autorequest on gpio_direction_{input,output}() in gpiolib
+When: February 2010
+Why: All callers should use explicit gpio_request()/gpio_free().
+ The autorequest mechanism in gpiolib was provided mostly as a
+ migration aid for legacy GPIO interfaces (for SOC based GPIOs).
+ Those users have now largely migrated. Platforms implementing
+ the GPIO interfaces without using gpiolib will see no changes.
+Who: David Brownell <dbrownell@users.sourceforge.net>
+---------------------------
+
What: b43 support for firmware revision < 410
When: The schedule was July 2008, but it was decided that we are going to keep the
code as long as there are no major maintanance headaches.
diff --git a/Documentation/gpio.txt b/Documentation/gpio.txt
index b1b9887..145c25a 100644
--- a/Documentation/gpio.txt
+++ b/Documentation/gpio.txt
@@ -123,7 +123,10 @@
Using GPIOs
-----------
-One of the first things to do with a GPIO, often in board setup code when
+The first thing a system should do with a GPIO is allocate it, using
+the gpio_request() call; see later.
+
+One of the next things to do with a GPIO, often in board setup code when
setting up a platform_device using the GPIO, is mark its direction:
/* set as input or output, returning 0 or negative errno */
@@ -141,8 +144,8 @@
For compatibility with legacy interfaces to GPIOs, setting the direction
of a GPIO implicitly requests that GPIO (see below) if it has not been
-requested already. That compatibility may be removed in the future;
-explicitly requesting GPIOs is strongly preferred.
+requested already. That compatibility is being removed from the optional
+gpiolib framework.
Setting the direction can fail if the GPIO number is invalid, or when
that particular GPIO can't be used in that mode. It's generally a bad
@@ -195,7 +198,7 @@
Platforms that support this type of GPIO distinguish them from other GPIOs
by returning nonzero from this call (which requires a valid GPIO number,
-either explicitly or implicitly requested):
+which should have been previously allocated with gpio_request):
int gpio_cansleep(unsigned gpio);
@@ -212,10 +215,9 @@
same as the spinlock-safe calls.
-Claiming and Releasing GPIOs (OPTIONAL)
----------------------------------------
+Claiming and Releasing GPIOs
+----------------------------
To help catch system configuration errors, two calls are defined.
-However, many platforms don't currently support this mechanism.
/* request GPIO, returning 0 or negative errno.
* non-null labels may be useful for diagnostics.
@@ -244,13 +246,6 @@
power management, such as by powering down unused chip sectors and, more
easily, gating off unused clocks.
-These two calls are optional because not not all current Linux platforms
-offer such functionality in their GPIO support; a valid implementation
-could return success for all gpio_request() calls. Unlike the other calls,
-the state they represent doesn't normally match anything from a hardware
-register; it's just a software bitmap which clearly is not necessary for
-correct operation of hardware or (bug free) drivers.
-
Note that requesting a GPIO does NOT cause it to be configured in any
way; it just marks that GPIO as in use. Separate code must handle any
pin setup (e.g. controlling which pin the GPIO uses, pullup/pulldown).
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 83c3fe3..51a8d41 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -69,20 +69,24 @@
* those calls have no teeth) we can't avoid autorequesting. This nag
* message should motivate switching to explicit requests... so should
* the weaker cleanup after faults, compared to gpio_request().
+ *
+ * NOTE: the autorequest mechanism is going away; at this point it's
+ * only "legal" in the sense that (old) code using it won't break yet,
+ * but instead only triggers a WARN() stack dump.
*/
static int gpio_ensure_requested(struct gpio_desc *desc, unsigned offset)
{
- if (test_and_set_bit(FLAG_REQUESTED, &desc->flags) == 0) {
- struct gpio_chip *chip = desc->chip;
- int gpio = chip->base + offset;
+ const struct gpio_chip *chip = desc->chip;
+ const int gpio = chip->base + offset;
+ if (WARN(test_and_set_bit(FLAG_REQUESTED, &desc->flags) == 0,
+ "autorequest GPIO-%d\n", gpio)) {
if (!try_module_get(chip->owner)) {
pr_err("GPIO-%d: module can't be gotten \n", gpio);
clear_bit(FLAG_REQUESTED, &desc->flags);
/* lose */
return -EIO;
}
- pr_warning("GPIO-%d autorequested\n", gpio);
desc_set_label(desc, "[auto]");
/* caller must chip->request() w/o spinlock */
if (chip->request)
