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>

1 files changed, 8 insertions, 4 deletions

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 83c3fe3a136b..51a8d4103be5 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -69,20 +69,24 @@ static inline void desc_set_label(struct gpio_desc *d, const char *label)
  * 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)