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Subject[PATCH 1/4] gpiolib: Introduce chip addition/removal notifier
Some platforms (e.g. OpenFirmware) want to know when a particular chip
added or removed, so that the platforms could add their specifics for
non-platform devices, like I2C or SPI GPIO chips.

This patch implements the notifier for chip addition and removal events.

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
---
drivers/gpio/Kconfig | 7 +++++++
drivers/gpio/gpiolib.c | 28 ++++++++++++++++++++++++++++
include/asm-generic/gpio.h | 8 ++++++++
3 files changed, 43 insertions(+), 0 deletions(-)

diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index 1f1d88a..511b29f 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -63,6 +63,13 @@ config GPIO_SYSFS
Kernel drivers may also request that a particular GPIO be
exported to userspace; this can be useful when debugging.

+config GPIOLIB_NOTIFIER
+ bool
+ help
+ This symbol is selected by subsystems that need to handle GPIO
+ chips addition and removal. E.g., this is used for the
+ OpenFirmware bindings.
+
# put expanders in the right section, in alphabetical order

comment "Memory mapped GPIO expanders:"
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 350842a..9496b78 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -9,6 +9,7 @@
#include <linux/seq_file.h>
#include <linux/gpio.h>
#include <linux/idr.h>
+#include <linux/notifier.h>


/* Optional implementation infrastructure for GPIO interfaces.
@@ -82,6 +83,25 @@ static inline void desc_set_label(struct gpio_desc *d, const char *label)
#endif
}

+#ifdef CONFIG_GPIOLIB_NOTIFIER
+BLOCKING_NOTIFIER_HEAD(gpio_notifier);
+EXPORT_SYMBOL_GPL(gpio_notifier);
+
+static int gpio_call_chain(struct gpio_chip *chip, enum gpio_notify_msg msg)
+{
+ int ret;
+
+ ret = blocking_notifier_call_chain(&gpio_notifier, msg, chip);
+
+ return notifier_to_errno(ret);
+}
+#else
+static int gpio_call_chain(struct gpio_chip *chip, enum gpio_notify_msg msg)
+{
+ return notifier_to_errno(NOTIFY_OK);
+}
+#endif /* CONFIG_GPIOLIB_NOTIFIER */
+
/* Warn when drivers omit gpio_request() calls -- legal but ill-advised
* when setting direction, and otherwise illegal. Until board setup code
* and drivers use explicit requests everywhere (which won't happen when
@@ -1103,6 +1123,9 @@ fail:
pr_err("gpiochip_add: gpios %d..%d (%s) not registered\n",
chip->base, chip->base + chip->ngpio - 1,
chip->label ? : "generic");
+ else
+ gpio_call_chain(chip, GPIO_NOTIFY_CHIP_ADDED);
+
return status;
}
EXPORT_SYMBOL_GPL(gpiochip_add);
@@ -1119,6 +1142,11 @@ int gpiochip_remove(struct gpio_chip *chip)
int status = 0;
unsigned id;

+ /* Ask external subsystems to release the chip. */
+ status = gpio_call_chain(chip, GPIO_NOTIFY_CHIP_REMOVE);
+ if (status)
+ return status;
+
spin_lock_irqsave(&gpio_lock, flags);

for (id = chip->base; id < chip->base + chip->ngpio; id++) {
diff --git a/include/asm-generic/gpio.h b/include/asm-generic/gpio.h
index 485eeb6..84faae4 100644
--- a/include/asm-generic/gpio.h
+++ b/include/asm-generic/gpio.h
@@ -4,6 +4,7 @@
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/errno.h>
+#include <linux/notifier.h>

#ifdef CONFIG_GPIOLIB

@@ -208,4 +209,11 @@ static inline void gpio_unexport(unsigned gpio)
}
#endif /* CONFIG_GPIO_SYSFS */

+enum gpio_notify_msg {
+ GPIO_NOTIFY_CHIP_ADDED = 0,
+ GPIO_NOTIFY_CHIP_REMOVE = 1,
+};
+
+extern struct blocking_notifier_head gpio_notifier;
+
#endif /* _ASM_GENERIC_GPIO_H */
--
1.6.5.7


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