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117 lines
3.4 KiB
Diff
117 lines
3.4 KiB
Diff
From: Anton Vorontsov <avorontsov@ru.mvista.com>
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Date: Mon, 28 Apr 2008 09:14:46 +0000 (-0700)
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Subject: gpiolib: dynamic gpio number allocation
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X-Git-Tag: v2.6.26-rc1~848
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X-Git-Url: http://git.kernel.org/?p=linux%2Fkernel%2Fgit%2Ftorvalds%2Flinux-2.6.git;a=commitdiff_plain;h=8d0aab2f16c4fa170f32e7a74a52cd0122bbafef
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gpiolib: dynamic gpio number allocation
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If gpio_chip->base is negative during registration, gpiolib performs dynamic
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base allocation. This is useful for devices that aren't always present, such
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as GPIOs on hotplugged devices rather than mainboards. (This behavior was
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previously specified but not implemented.)
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To avoid using any numbers that may have been explicitly assigned but not yet
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registered, this dynamic allocation assigns GPIO numbers from the biggest
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number on down, instead of from the smallest on up.
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Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
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Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
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Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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---
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--- a/drivers/gpio/gpiolib.c
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+++ b/drivers/gpio/gpiolib.c
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@@ -80,6 +80,33 @@ static inline struct gpio_chip *gpio_to_
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return gpio_desc[gpio].chip;
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}
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+/* dynamic allocation of GPIOs, e.g. on a hotplugged device */
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+static int gpiochip_find_base(int ngpio)
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+{
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+ int i;
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+ int spare = 0;
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+ int base = -ENOSPC;
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+
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+ for (i = ARCH_NR_GPIOS - 1; i >= 0 ; i--) {
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+ struct gpio_chip *chip = gpio_desc[i].chip;
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+
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+ if (!chip) {
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+ spare++;
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+ if (spare == ngpio) {
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+ base = i;
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+ break;
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+ }
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+ } else {
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+ spare = 0;
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+ i -= chip->ngpio - 1;
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+ }
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+ }
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+
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+ if (gpio_is_valid(base))
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+ pr_debug("%s: found new base at %d\n", __func__, base);
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+ return base;
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+}
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+
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/**
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* gpiochip_add() - register a gpio_chip
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* @chip: the chip to register, with chip->base initialized
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@@ -88,38 +115,49 @@ static inline struct gpio_chip *gpio_to_
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* Returns a negative errno if the chip can't be registered, such as
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* because the chip->base is invalid or already associated with a
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* different chip. Otherwise it returns zero as a success code.
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+ *
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+ * If chip->base is negative, this requests dynamic assignment of
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+ * a range of valid GPIOs.
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*/
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int gpiochip_add(struct gpio_chip *chip)
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{
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unsigned long flags;
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int status = 0;
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unsigned id;
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+ int base = chip->base;
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- /* NOTE chip->base negative is reserved to mean a request for
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- * dynamic allocation. We don't currently support that.
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- */
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-
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- if (chip->base < 0 || !gpio_is_valid(chip->base + chip->ngpio)) {
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+ if ((!gpio_is_valid(base) || !gpio_is_valid(base + chip->ngpio))
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+ && base >= 0) {
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status = -EINVAL;
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goto fail;
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}
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spin_lock_irqsave(&gpio_lock, flags);
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+ if (base < 0) {
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+ base = gpiochip_find_base(chip->ngpio);
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+ if (base < 0) {
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+ status = base;
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+ goto fail_unlock;
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+ }
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+ chip->base = base;
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+ }
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+
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/* these GPIO numbers must not be managed by another gpio_chip */
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- for (id = chip->base; id < chip->base + chip->ngpio; id++) {
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+ for (id = base; id < base + chip->ngpio; id++) {
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if (gpio_desc[id].chip != NULL) {
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status = -EBUSY;
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break;
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}
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}
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if (status == 0) {
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- for (id = chip->base; id < chip->base + chip->ngpio; id++) {
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+ for (id = base; id < base + chip->ngpio; id++) {
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gpio_desc[id].chip = chip;
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gpio_desc[id].flags = 0;
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}
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}
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+fail_unlock:
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spin_unlock_irqrestore(&gpio_lock, flags);
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fail:
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/* failures here can mean systems won't boot... */
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