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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>
hifive-unleashed-5.1
Guennadi Liakhovetski 2008-04-28 02:14:44 -07:00 committed by Linus Torvalds
parent 73fcdc9e15
commit 438d8908b3
2 changed files with 14 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
drivers/gpio/gpiolib.c
View File

@ -68,6 +68,9 @@ static void gpio_ensure_requested(struct gpio_desc *desc)
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 char *label)
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 char *label)
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);

2
include/asm-generic/gpio.h
View File

@ -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);