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From: Guennadi Liakhovetski <g.liakhovetski@pengutronix.de>
Date: Mon, 28 Apr 2008 09:14:44 +0000 (-0700)
Subject: gpiolib: better rmmod infrastructure
X-Git-Tag: v2.6.26-rc1~851
X-Git-Url: http://git.kernel.org/?p=linux%2Fkernel%2Fgit%2Ftorvalds%2Flinux-2.6.git;a=commitdiff_plain;h=438d8908b379b6322fc3b28d45c9ebdddf58bc20
gpiolib: better rmmod infrastructure
As long as one or more GPIOs on a gpio chip are used its driver should not be
unloaded. The existing mechanism (gpiochip_remove failure) doesn't address
that, since rmmod can no longer be made to fail by having the cleanup code
report errors. Module usecounts are the solution.
Assuming standard "initialize struct to zero" policies, this change won't
affect SOC platform drivers. However, drivers for external chips (on I2C and
SPI busses) should be updated if they can be built as modules.
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@pengutronix.de>
[ gpio_ensure_requested() needs to update module usecounts too ]
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -68,6 +68,9 @@ static void gpio_ensure_requested(struct
if (test_and_set_bit(FLAG_REQUESTED, &desc->flags) == 0) {
pr_warning("GPIO-%d autorequested\n", (int)(desc - gpio_desc));
desc_set_label(desc, "[auto]");
+ if (!try_module_get(desc->chip->owner))
+ pr_err("GPIO-%d: module can't be gotten \n",
+ (int)(desc - gpio_desc));
}
}
@@ -177,6 +180,9 @@ int gpio_request(unsigned gpio, const ch
if (desc->chip == NULL)
goto done;
+ if (!try_module_get(desc->chip->owner))
+ goto done;
+
/* NOTE: gpio_request() can be called in early boot,
* before IRQs are enabled.
*/
@@ -184,8 +190,10 @@ int gpio_request(unsigned gpio, const ch
if (test_and_set_bit(FLAG_REQUESTED, &desc->flags) == 0) {
desc_set_label(desc, label ? : "?");
status = 0;
- } else
+ } else {
status = -EBUSY;
+ module_put(desc->chip->owner);
+ }
done:
if (status)
@@ -209,9 +217,10 @@ void gpio_free(unsigned gpio)
spin_lock_irqsave(&gpio_lock, flags);
desc = &gpio_desc[gpio];
- if (desc->chip && test_and_clear_bit(FLAG_REQUESTED, &desc->flags))
+ if (desc->chip && test_and_clear_bit(FLAG_REQUESTED, &desc->flags)) {
desc_set_label(desc, NULL);
- else
+ module_put(desc->chip->owner);
+ } else
WARN_ON(extra_checks);
spin_unlock_irqrestore(&gpio_lock, flags);
--- a/include/asm-generic/gpio.h
+++ b/include/asm-generic/gpio.h
@@ -17,6 +17,7 @@
#endif
struct seq_file;
+struct module;
/**
* struct gpio_chip - abstract a GPIO controller
@@ -48,6 +49,7 @@ struct seq_file;
*/
struct gpio_chip {
char *label;
+ struct module *owner;
int (*direction_input)(struct gpio_chip *chip,
unsigned offset);
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