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[PATCH] EM28xx - replug locking cleanup



Mauro,

This patch simplifies the locking by moving the em28xx_init_extension() call until em28xx_usb_probe() has finished with the dev->lock mutex. It therefore makes the second and subsequent "plugging" events logically identical to the first "plugging" event when the em28xx-dvb and em28xx-alsa modules must be loaded (i.e. registered).

Basically, em28xx_usb_probe() requests that em28xx-dvb be loaded and also triggers udev to initialise the V4L2 devices. These two events are serialised by the dev->lock mutex but the order that they happen in is undefined. But this has always been the case anyway.

Signed-off-by: Chris Rankin <rankincj@xxxxxxxxx>

Cheers,
Chris
--- linux/drivers/media/video/em28xx/em28xx-cards.c.orig	2011-09-25 22:51:59.000000000 +0100
+++ linux/drivers/media/video/em28xx/em28xx-cards.c	2011-09-25 23:24:06.000000000 +0100
@@ -3005,10 +3005,6 @@
 		goto fail;
 	}
 
-	mutex_unlock(&dev->lock);
-	em28xx_init_extension(dev);
-	mutex_lock(&dev->lock);
-
 	/* Save some power by putting tuner to sleep */
 	v4l2_device_call_all(&dev->v4l2_dev, 0, core, s_power, 0);
 
@@ -3243,6 +3239,13 @@
 	 */
 	mutex_unlock(&dev->lock);
 
+	/*
+	 * These extensions can be modules. If the modules are already
+	 * loaded then we can initialise the device now, otherwise we
+	 * will initialise it when the modules load instead.
+	 */
+	em28xx_init_extension(dev);
+
 	return 0;
 
 err:

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