[RFC][PATCH -mm 3/3] PM: Disable _request_firmware before hibernation/suspend

["Rafael J. Wysocki" <rjw@sisk.pl>]

From: Rafael J. Wysocki <rjw@sisk.pl>

Use a hibernation and suspend notifier to disable the firmware requesting
mechanism before a hibernation/suspend and enable it after the operation.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>

 drivers/base/firmware_class.c |   36 ++++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)

Index: linux-2.6.22-rc3/drivers/base/firmware_class.c
===================================================================
--- linux-2.6.22-rc3.orig/drivers/base/firmware_class.c	2007-05-27 19:43:03.000000000 +0200
+++ linux-2.6.22-rc3/drivers/base/firmware_class.c	2007-05-27 19:44:06.000000000 +0200
@@ -17,6 +17,8 @@
 #include <linux/bitops.h>
 #include <linux/mutex.h>
 #include <linux/kthread.h>
+#include <linux/notifier.h>
+#include <linux/suspend.h>
 
 #include <linux/firmware.h>
 #include "base.h"
@@ -35,6 +37,9 @@ enum {
 
 static int loading_timeout = 60;	/* In seconds */
 
+/* If set, _request_firmware() will exit immediately returning -EBUSY */
+static int requesting_firmware_disabled;
+
 /* fw_lock could be moved to 'struct firmware_priv' but since it is just
  * guarding for corner cases a global lock should be OK */
 static DEFINE_MUTEX(fw_lock);
@@ -397,6 +402,9 @@ _request_firmware(const struct firmware 
 	struct firmware *firmware;
 	int retval;
 
+	if (requesting_firmware_disabled)
+		return -EBUSY;
+
 	if (!firmware_p)
 		return -EINVAL;
 
@@ -568,6 +576,26 @@ request_firmware_nowait(
 	return 0;
 }
 
+static int firmware_class_pm_callback(struct notifier_block *nfb,
+					unsigned long action,
+					void *ignored)
+{
+	switch (action) {
+	case PM_PRE_FREEZE:
+		requesting_firmware_disabled = 1;
+		return NOTIFY_OK;
+	case PM_POST_THAW:
+		requesting_firmware_disabled = 0;
+		return NOTIFY_OK;
+	}
+
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block firmware_class_pm_nb = {
+	.notifier_call  = firmware_class_pm_callback,
+};
+
 static int __init
 firmware_class_init(void)
 {
@@ -582,6 +610,13 @@ firmware_class_init(void)
 		printk(KERN_ERR "%s: class_create_file failed\n",
 		       __FUNCTION__);
 		class_unregister(&firmware_class);
+		return error;
+	}
+	error = register_pm_notifier(&firmware_class_pm_nb);
+	if (error) {
+		printk(KERN_ERR "%s: register_pm_notifier failed\n",
+		       __FUNCTION__);
+		class_unregister(&firmware_class);
 	}
 	return error;
 
@@ -589,6 +624,7 @@ firmware_class_init(void)
 static void __exit
 firmware_class_exit(void)
 {
+	unregister_pm_notifier(&firmware_class_pm_nb);
 	class_unregister(&firmware_class);
 }