linux-kernel - [PATCH 5/9] gpiolib: use gpio_chips list in gpiochip_find

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Date:	Sun,  3 Feb 2013 01:29:28 +0900
From:	Alexandre Courbot <acourbot@...dia.com>
To:	Grant Likely <grant.likely@...retlab.ca>,
	Linus Walleij <linus.walleij@...aro.org>,
	Arnd Bergmann <arnd@...db.de>
Cc:	linux-arch@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org, gnurou@...il.com,
	Alexandre Courbot <acourbot@...dia.com>
Subject: [PATCH 5/9] gpiolib: use gpio_chips list in gpiochip_find_base

Re-implement gpiochip_find_base using the list of chips instead of the
global gpio_desc[] array. This makes it both simpler and more efficient,
and is needed to remove the global descriptors array.

Signed-off-by: Alexandre Courbot <acourbot@...dia.com>
---
 drivers/gpio/gpiolib.c | 37 ++++++++++++++++---------------------
 1 file changed, 16 insertions(+), 21 deletions(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index e473ded..af4c350 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -126,30 +126,25 @@ struct gpio_chip *gpio_to_chip(unsigned gpio)
 /* dynamic allocation of GPIOs, e.g. on a hotplugged device */
 static int gpiochip_find_base(int ngpio)
 {
-	int i;
-	int spare = 0;
-	int base = -ENOSPC;
-
-	for (i = ARCH_NR_GPIOS - 1; i >= 0 ; i--) {
-		struct gpio_desc *desc = &gpio_desc[i];
-		struct gpio_chip *chip = desc->chip;
-
-		if (!chip) {
-			spare++;
-			if (spare == ngpio) {
-				base = i;
-				break;
-			}
-		} else {
-			spare = 0;
-			if (chip)
-				i -= chip->ngpio - 1;
-		}
+	struct gpio_chip *chip;
+	int base = ARCH_NR_GPIOS - ngpio;
+
+	list_for_each_entry_reverse(chip, &gpio_chips, list) {
+		/* found a free space? */
+		if (chip->base + chip->ngpio <= base)
+			break;
+		else
+			/* nope, check the space right before the chip */
+			base = chip->base - ngpio;
 	}
 
-	if (gpio_is_valid(base))
+	if (gpio_is_valid(base)) {
 		pr_debug("%s: found new base at %d\n", __func__, base);
-	return base;
+		return base;
+	} else {
+		pr_err("%s: cannot find free range\n", __func__);
+		return -ENOSPC;
+	}
 }
 
 /* caller ensures gpio is valid and requested, chip->get_direction may sleep  */
-- 
1.8.1.1

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