Re: [patch/rfc 1/4] GPIO implementation framework

["eric miao" <eric.y.miao@gmail.com>]

Here comes the point of "struct gpio_desc"

Subject: [PATCH 3/5] use a per GPIO "struct gpio_desc" and chain
"gpio_chip" to a list

---
 include/asm-generic/gpio.h |    7 +++++
 lib/gpiolib.c              |   64 ++++++++++++++++++++++----------------------
 2 files changed, 39 insertions(+), 32 deletions(-)

diff --git a/include/asm-generic/gpio.h b/include/asm-generic/gpio.h
index ba3e336..783adcf 100644
--- a/include/asm-generic/gpio.h
+++ b/include/asm-generic/gpio.h
@@ -23,6 +23,12 @@

 struct seq_file;

+struct gpio_chip;
+
+struct gpio_desc {
+	struct gpio_chip *chip;
+};
+
 /**
  * struct gpio_chip - abstract a GPIO controller
  * @label: for diagnostics
@@ -76,6 +82,7 @@ struct gpio_chip {
 	DECLARE_BITMAP(requested, ARCH_GPIOS_PER_CHIP);

 #ifdef CONFIG_DEBUG_FS
+	struct list_head	node;
 	const char		*requested_str[ARCH_GPIOS_PER_CHIP];
 #endif
 };
diff --git a/lib/gpiolib.c b/lib/gpiolib.c
index d52c7f1..57e0d10 100644
--- a/lib/gpiolib.c
+++ b/lib/gpiolib.c
@@ -25,13 +25,12 @@
 #define	extra_checks	0
 #endif

-/* gpio_lock protects modification to the table of chips and to
- * gpio_chip->requested.  If a gpio is requested, its gpio_chip
- * is not removable.
- */
 static DEFINE_SPINLOCK(gpio_lock);
-static struct gpio_chip *chips[DIV_ROUND_UP(ARCH_NR_GPIOS,
-					ARCH_GPIOS_PER_CHIP)];
+struct gpio_desc gpio_desc[ARCH_NR_GPIOS];
+
+#ifdef CONFIG_DEBUG_FS
+static LIST_HEAD(gpio_chip_list);
+#endif

 static inline int gpio_is_onchip(unsigned gpio, struct gpio_chip *chip)
 {
@@ -63,7 +62,7 @@ static void gpio_ensure_requested(struct gpio_chip
*chip, unsigned offset)
 /* caller holds gpio_lock */
 static inline struct gpio_chip *gpio_to_chip(unsigned gpio)
 {
-	return chips[gpio / ARCH_GPIOS_PER_CHIP];
+	return gpio_desc[gpio].chip;
 }

 /**
@@ -78,7 +77,6 @@ static inline struct gpio_chip *gpio_to_chip(unsigned gpio)
 int gpiochip_add(struct gpio_chip *chip)
 {
 	unsigned long	flags;
-	int		status = 0;
 	unsigned	id;

 	if (chip->base < 0 || (chip->base % ARCH_GPIOS_PER_CHIP) != 0)
@@ -89,13 +87,21 @@ int gpiochip_add(struct gpio_chip *chip)
 		return -EINVAL;

 	spin_lock_irqsave(&gpio_lock, flags);
-	id = chip->base / ARCH_GPIOS_PER_CHIP;
-	if (chips[id] == NULL)
-		chips[id] = chip;
-	else
-		status = -EBUSY;
+
+	for (id = chip->base; id < chip->base + chip->ngpio; id++)
+		if (gpio_desc[id].chip) {
+			spin_unlock_irqrestore(&gpio_lock, flags);
+			return -EBUSY;
+		}
+
+	for (id = chip->base; id < chip->base + chip->ngpio; id++)
+		gpio_desc[id].chip = chip;
+
+#ifdef CONFIG_DEBUG_FS
+	list_add(&chip->node, &gpio_chip_list);
+#endif
 	spin_unlock_irqrestore(&gpio_lock, flags);
-	return status;
+	return 0;
 }
 EXPORT_SYMBOL_GPL(gpiochip_add);

@@ -108,28 +114,26 @@ EXPORT_SYMBOL_GPL(gpiochip_add);
 int gpiochip_remove(struct gpio_chip *chip)
 {
 	unsigned long	flags;
-	int		status = 0;
 	int		offset;
-	unsigned	id = chip->base / ARCH_GPIOS_PER_CHIP;
+	unsigned	id;

 	spin_lock_irqsave(&gpio_lock, flags);

-	for (offset = 0; offset < chip->ngpio; offset++) {
+	for (offset = 0; offset < chip->ngpio; offset++)
 		if (gpiochip_is_requested(chip, offset)) {
-			status = -EBUSY;
-			break;
+			spin_unlock_irqrestore(&gpio_lock, flags);
+			return -EBUSY;
 		}
-	}

-	if (status == 0) {
-		if (chips[id] == chip)
-			chips[id] = NULL;
-		else
-			status = -EINVAL;
-	}
+	for (id = chip->base; id < chip->base + chip->ngpio; id++)
+		gpio_desc[id].chip = NULL;
+
+#ifdef CONFIG_DEBUG_FS
+	list_del(&chip->node);
+#endif

 	spin_unlock_irqrestore(&gpio_lock, flags);
-	return status;
+	return 0;
 }
 EXPORT_SYMBOL_GPL(gpiochip_remove);

@@ -463,11 +467,7 @@ static int gpiolib_show(struct seq_file *s, void *unused)

 	/* REVISIT this isn't locked against gpio_chip removal ... */

-	for (id = 0; id < ARRAY_SIZE(chips); id++) {
-		chip = chips[id];
-		if (!chip)
-			continue;
-
+	list_for_each_entry(chip, &gpio_chip_list, node) {
 		seq_printf(s, "%sGPIOs %d-%d, %s%s:\n",
 				started ? "\n" : "",
 				chip->base, chip->base + chip->ngpio - 1,
-- 
1.5.2.5.GIT