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Date: Wed, 14 Nov 2007 09:03:29 +0800
From: "eric miao" <eric.y.miao@...il.com>
To: "David Brownell" <david-b@...bell.net>
Cc: "Linux Kernel list" <linux-kernel@...r.kernel.org>,
"Felipe Balbi" <felipebalbi@...rs.sourceforge.net>,
"Bill Gatliff" <bgat@...lgatliff.com>,
"Haavard Skinnemoen" <hskinnemoen@...el.com>,
"Andrew Victor" <andrew@...people.com>,
"Tony Lindgren" <tony@...mide.com>,
"Jean Delvare" <khali@...ux-fr.org>,
"Kevin Hilman" <khilman@...sta.com>,
"Paul Mundt" <lethal@...ux-sh.org>,
"Ben Dooks" <ben@...nity.fluff.org>
Subject: Re: [patch/rfc 1/4] GPIO implementation framework
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
-
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