target/linux/generic-2.6/patches-2.6.25/960-backport_gpiolib_better_rmmod_infrastructure.patch

   1 From: Guennadi Liakhovetski <g.liakhovetski@pengutronix.de>
   2 Date: Mon, 28 Apr 2008 09:14:44 +0000 (-0700)
   3 Subject: gpiolib: better rmmod infrastructure
   4 X-Git-Tag: v2.6.26-rc1~851
   5 X-Git-Url: http://git.kernel.org/?p=linux%2Fkernel%2Fgit%2Ftorvalds%2Flinux-2.6.git;a=commitdiff_plain;h=438d8908b379b6322fc3b28d45c9ebdddf58bc20
   6
   7 gpiolib: better rmmod infrastructure
   8
   9 As long as one or more GPIOs on a gpio chip are used its driver should not be
  10 unloaded.  The existing mechanism (gpiochip_remove failure) doesn't address
  11 that, since rmmod can no longer be made to fail by having the cleanup code
  12 report errors.  Module usecounts are the solution.
  13
  14 Assuming standard "initialize struct to zero" policies, this change won't
  15 affect SOC platform drivers.  However, drivers for external chips (on I2C and
  16 SPI busses) should be updated if they can be built as modules.
  17
  18 Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@pengutronix.de>
  19 [ gpio_ensure_requested() needs to update module usecounts too ]
  20 Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
  21 Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
  22 Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
  23 ---
  24
  25 --- a/drivers/gpio/gpiolib.c
  26 +++ b/drivers/gpio/gpiolib.c
  27 @@ -68,6 +68,9 @@ static void gpio_ensure_requested(struct
  28         if (test_and_set_bit(FLAG_REQUESTED, &desc->flags) == 0) {
  29                 pr_warning("GPIO-%d autorequested\n", (int)(desc - gpio_desc));
  30                 desc_set_label(desc, "[auto]");
  31 +               if (!try_module_get(desc->chip->owner))
  32 +                       pr_err("GPIO-%d: module can't be gotten \n",
  33 +                                       (int)(desc - gpio_desc));
  34         }
  35  }
  36
  37 @@ -177,6 +180,9 @@ int gpio_request(unsigned gpio, const ch
  38         if (desc->chip == NULL)
  39                 goto done;
  40
  41 +       if (!try_module_get(desc->chip->owner))
  42 +               goto done;
  43 +
  44         /* NOTE:  gpio_request() can be called in early boot,
  45          * before IRQs are enabled.
  46          */
  47 @@ -184,8 +190,10 @@ int gpio_request(unsigned gpio, const ch
  48         if (test_and_set_bit(FLAG_REQUESTED, &desc->flags) == 0) {
  49                 desc_set_label(desc, label ? : "?");
  50                 status = 0;
  51 -       } else
  52 +       } else {
  53                 status = -EBUSY;
  54 +               module_put(desc->chip->owner);
  55 +       }
  56
  57  done:
  58         if (status)
  59 @@ -209,9 +217,10 @@ void gpio_free(unsigned gpio)
  60         spin_lock_irqsave(&gpio_lock, flags);
  61
  62         desc = &gpio_desc[gpio];
  63 -       if (desc->chip && test_and_clear_bit(FLAG_REQUESTED, &desc->flags))
  64 +       if (desc->chip && test_and_clear_bit(FLAG_REQUESTED, &desc->flags)) {
  65                 desc_set_label(desc, NULL);
  66 -       else
  67 +               module_put(desc->chip->owner);
  68 +       } else
  69                 WARN_ON(extra_checks);
  70
  71         spin_unlock_irqrestore(&gpio_lock, flags);
  72 --- a/include/asm-generic/gpio.h
  73 +++ b/include/asm-generic/gpio.h
  74 @@ -17,6 +17,7 @@
  75  #endif
  76
  77  struct seq_file;
  78 +struct module;
  79
  80  /**
  81   * struct gpio_chip - abstract a GPIO controller
  82 @@ -48,6 +49,7 @@ struct seq_file;
  83   */
  84  struct gpio_chip {
  85         char                    *label;
  86 +       struct module           *owner;
  87
  88         int                     (*direction_input)(struct gpio_chip *chip,
  89                                                 unsigned offset);