hwrng: Add type categories

Index: bu3sch-wireless-dev/drivers/char/hw_random/core.c
===================================================================
@@ -78,6 +78,20 @@ static inline int hwrng_data_read(struct
 	return rng->data_read(rng, data);
 }
 
+static const char * hwrng_type_string(enum hwrng_type type)
+{
+	switch (type) {
+	case HWRNG_TYPE_DEDIC:
+		return "dedicated";
+	case HWRNG_TYPE_ONBOARD:
+		return "onboard";
+	case HWRNG_TYPE_BAD:
+		return "bad";
+	case HWRNG_TYPE_PSEUDO:
+		return "pseudo";
+	}
+	return "unknown";
+}
 
 static int rng_dev_open(struct inode *inode, struct file *filp)
 {

@@ -210,7 +224,7 @@ static ssize_t hwrng_attr_current_show(s
 	ret = snprintf(buf, PAGE_SIZE, "%s\n", name);
 	mutex_unlock(&rng_mutex);
 
-	return ret;
+	return min(ret, (ssize_t)PAGE_SIZE);
 }
 
 static ssize_t hwrng_attr_available_show(struct device *dev,

@@ -235,7 +249,36 @@ static ssize_t hwrng_attr_available_show
 	ret++;
 	mutex_unlock(&rng_mutex);
 
-	return ret;
+	return min(ret, (ssize_t)PAGE_SIZE);
+}
+
+static ssize_t hwrng_attr_types_show(struct device *dev,
+				     struct device_attribute *attr,
+				     char *buf)
+{
+	int err;
+	ssize_t ret = 0;
+	struct hwrng *rng;
+	const char *type;
+
+	err = mutex_lock_interruptible(&rng_mutex);
+	if (err)
+		return -ERESTARTSYS;
+	buf[0] = '\0';
+	list_for_each_entry(rng, &rng_list, list) {
+		strncat(buf, rng->name, PAGE_SIZE - ret - 1);
+		ret += strlen(rng->name);
+		strncat(buf, " type: \"", PAGE_SIZE - ret - 1);
+		ret += 8;
+		type = hwrng_type_string(rng->type);
+		strncat(buf, type, PAGE_SIZE - ret - 1);
+		ret += strlen(type);
+		strncat(buf, "\"\n", PAGE_SIZE - ret - 1);
+		ret += 2;
+	}
+	mutex_unlock(&rng_mutex);
+
+	return min(ret, (ssize_t)PAGE_SIZE);
 }
 
 static DEVICE_ATTR(rng_current, S_IRUGO | S_IWUSR,

@@ -244,10 +287,58 @@ static DEVICE_ATTR(rng_current, S_IRUGO 
 static DEVICE_ATTR(rng_available, S_IRUGO,
 		   hwrng_attr_available_show,
 		   NULL);
+static DEVICE_ATTR(rng_types, S_IRUGO,
+		   hwrng_attr_types_show,
+		   NULL);
+
+
+/* Returns the RNG with the highest type value
+ * Expects rng_mutex locked. */
+static struct hwrng * select_best_hwrng(void)
+{
+	struct hwrng *rng, *ret = NULL;
+
+	list_for_each_entry(rng, &rng_list, list) {
+		if (!ret || (rng->type > ret->type))
+			ret = rng;
+	}
+
+	return ret;
+}
+
+/* Initializes the RNG with the highest type value.
+ * Expects rng_mutex locked. */
+static int init_best_hwrng(void)
+{
+	struct hwrng *rng, *prev_rng = NULL;
+	int err;
 
+	rng = select_best_hwrng();
+	if (!rng)
+		return -ENODEV;
+	if (rng == current_rng)
+		return 0;
+	if (current_rng) {
+		/* Shutdown current RNG */
+		prev_rng = current_rng;
+		hwrng_cleanup(current_rng);
+		current_rng = NULL;
+	}
+	err = hwrng_init(rng);
+	if (err) {
+		/* Try to enable the old one again. */
+		if (prev_rng && (hwrng_init(prev_rng) == 0))
+			current_rng = prev_rng;
+		return err;
+	}
+	current_rng = rng;
+
+	return 0;
+}
 
 static void unregister_miscdev(void)
 {
+	device_remove_file(rng_miscdev.this_device, &dev_attr_rng_types);
 	device_remove_file(rng_miscdev.this_device, &dev_attr_rng_available);
 	device_remove_file(rng_miscdev.this_device, &dev_attr_rng_current);
 	misc_deregister(&rng_miscdev);

@@ -268,9 +359,16 @@ static int register_miscdev(void)
 				 &dev_attr_rng_available);
 	if (err)
 		goto err_remove_current;
+	err = device_create_file(rng_miscdev.this_device,
+				 &dev_attr_rng_types);
+	if (err)
+		goto err_remove_available;
+
 out:
 	return err;
 
+err_remove_available:
+	device_remove_file(rng_miscdev.this_device, &dev_attr_rng_available);
 err_remove_current:
 	device_remove_file(rng_miscdev.this_device, &dev_attr_rng_current);
 err_misc_dereg:

@@ -282,7 +380,7 @@ int hwrng_register(struct hwrng *rng)
 {
 	int must_register_misc;
 	int err = -EINVAL;
-	struct hwrng *old_rng, *tmp;
+	struct hwrng *tmp;
 
 	if (rng->name == NULL ||
 	    rng->data_read == NULL)

@@ -297,27 +395,26 @@ int hwrng_register(struct hwrng *rng)
 			goto out_unlock;
 	}
 
-	must_register_misc = (current_rng == NULL);
-	old_rng = current_rng;
-	if (!old_rng) {
-		err = hwrng_init(rng);
-		if (err)
-			goto out_unlock;
-		current_rng = rng;
-	}
+	must_register_misc = list_empty(&rng_list);
+	INIT_LIST_HEAD(&rng->list);
+	list_add(&rng->list, &rng_list);
+
+	init_best_hwrng();
+	/* We ignore the error code of init_best_hwrng(), as
+	 * it doesn't matter for hwrng_register(). */
 	err = 0;
 	if (must_register_misc) {
 		err = register_miscdev();
 		if (err) {
-			if (!old_rng) {
-				hwrng_cleanup(rng);
+			if (current_rng) {
+				hwrng_cleanup(current_rng);
 				current_rng = NULL;
 			}
+			list_del(&rng->list);
 			goto out_unlock;
 		}
 	}
-	INIT_LIST_HEAD(&rng->list);
-	list_add_tail(&rng->list, &rng_list);
+
 out_unlock:
 	mutex_unlock(&rng_mutex);
 out:

@@ -327,21 +424,15 @@ EXPORT_SYMBOL_GPL(hwrng_register);
 
 void hwrng_unregister(struct hwrng *rng)
 {
-	int err;
-
 	mutex_lock(&rng_mutex);
 
 	list_del(&rng->list);
 	if (current_rng == rng) {
 		hwrng_cleanup(rng);
-		if (list_empty(&rng_list)) {
-			current_rng = NULL;
-		} else {
-			current_rng = list_entry(rng_list.prev, struct hwrng, list);
-			err = hwrng_init(current_rng);
-			if (err)
-				current_rng = NULL;
-		}
+		current_rng = NULL;
+		/* Now try to init another hwrng, if any.
+		 * We're not interested if this fails or not. */
+		init_best_hwrng();
 	}
 	if (list_empty(&rng_list))
 		unregister_miscdev();

Index: bu3sch-wireless-dev/include/linux/hw_random.h
===================================================================
@@ -16,6 +16,29 @@
 #include <linux/types.h>
 #include <linux/list.h>
 
+
+/**
+ * enum hwrng_type - Type identifier for RNG hardware
+ * @HWRNG_TYPE_DEDIC:	Dedicated RNG extension board/device.
+ * 			Use for special (non-onboard) RNG boards
+ * 			that gather entropy from good sources.
+ * @HWRNG_TYPE_ONBOARD:	Onboard-RNG or In-CPU-RNG devices.
+ * @HWRNG_TYPE_BAD:	RNG devices with an unknown quality of the
+ * 			entropy or entropy sources that could
+ * 			be influenced from outside (like normal radio
+ * 			receivers)
+ * @HWRNG_TYPE_PSEUDO:	Pseudo RNG device. Use this for devices
+ * 			which are not RNG devices by definition, but
+ * 			could be used as such. For example various
+ * 			hardware sensors, like a motion sensor.
+ */
+enum hwrng_type {
+	HWRNG_TYPE_DEDIC	= 3,
+	HWRNG_TYPE_ONBOARD	= 2,
+	HWRNG_TYPE_BAD		= 1,
+	HWRNG_TYPE_PSEUDO	= 0,
+};
+
 /**
  * struct hwrng - Hardware Random Number Generator driver
  * @name:		Unique RNG name.

@@ -28,6 +51,7 @@
  *			Returns the number of lower random bytes in "data".
  *			Must not be NULL.
  * @priv:		Private data, for use by the RNG driver.
+ * @type:		The type identifier of the RNG device.
  */
 struct hwrng {
 	const char *name;

@@ -36,6 +60,7 @@ struct hwrng {
 	int (*data_present)(struct hwrng *rng);
 	int (*data_read)(struct hwrng *rng, u32 *data);
 	unsigned long priv;
+	enum hwrng_type type;
 
 	/* internal. */
 	struct list_head list;

Index: bu3sch-wireless-dev/drivers/char/hw_random/amd-rng.c
===================================================================
@@ -99,6 +99,7 @@ static struct hwrng amd_rng = {
 	.cleanup	= amd_rng_cleanup,
 	.data_present	= amd_rng_data_present,
 	.data_read	= amd_rng_data_read,
+	.type		= HWRNG_TYPE_ONBOARD,
 };
 
 

Index: bu3sch-wireless-dev/drivers/char/hw_random/geode-rng.c
===================================================================
@@ -73,6 +73,7 @@ static struct hwrng geode_rng = {
 	.name		= "geode",
 	.data_present	= geode_rng_data_present,
 	.data_read	= geode_rng_data_read,
+	.type		= HWRNG_TYPE_ONBOARD,
 };
 
 

Index: bu3sch-wireless-dev/drivers/char/hw_random/intel-rng.c
===================================================================
@@ -216,6 +216,7 @@ static struct hwrng intel_rng = {
 	.cleanup	= intel_rng_cleanup,
 	.data_present	= intel_rng_data_present,
 	.data_read	= intel_rng_data_read,
+	.type		= HWRNG_TYPE_ONBOARD,
 };
 
 struct intel_rng_hw {

Index: bu3sch-wireless-dev/drivers/char/hw_random/ixp4xx-rng.c
===================================================================
@@ -38,6 +38,7 @@ static int ixp4xx_rng_data_read(struct h
 static struct hwrng ixp4xx_rng_ops = {
 	.name		= "ixp4xx",
 	.data_read	= ixp4xx_rng_data_read,
+	.type		= HWRNG_TYPE_ONBOARD,
 };
 
 static int __init ixp4xx_rng_init(void)

Index: bu3sch-wireless-dev/drivers/char/hw_random/pasemi-rng.c
===================================================================
@@ -137,6 +137,7 @@ static struct of_platform_driver rng_dri
 	.match_table	= rng_match,
 	.probe		= rng_probe,
 	.remove		= rng_remove,
+	.type		= HWRNG_TYPE_ONBOARD,
 };
 
 static int __init rng_init(void)

Index: bu3sch-wireless-dev/drivers/char/hw_random/via-rng.c
===================================================================
@@ -150,6 +150,7 @@ static struct hwrng via_rng = {
 	.init		= via_rng_init,
 	.data_present	= via_rng_data_present,
 	.data_read	= via_rng_data_read,
+	.type		= HWRNG_TYPE_ONBOARD,
 };
 
 

Index: bu3sch-wireless-dev/drivers/net/wireless/bcm43xx/bcm43xx_main.c
===================================================================
@@ -3278,6 +3278,7 @@ static int bcm43xx_rng_init(struct bcm43
 	bcm->rng.name = bcm->rng_name;
 	bcm->rng.data_read = bcm43xx_rng_read;
 	bcm->rng.priv = (unsigned long)bcm;
+	bcm->rng.type = HWRNG_TYPE_BAD;
 	err = hwrng_register(&bcm->rng);
 	if (err)
 		printk(KERN_ERR PFX "RNG init failed (%d)\n", err);

Index: bu3sch-wireless-dev/drivers/net/wireless/mac80211/bcm43xx/bcm43xx_main.c
===================================================================
@@ -2399,6 +2399,7 @@ static int bcm43xx_rng_init(struct bcm43
 	wl->rng.name = wl->rng_name;
 	wl->rng.data_read = bcm43xx_rng_read;
 	wl->rng.priv = (unsigned long)wl;
+	wl->rng.type = HWRNG_TYPE_BAD;
 	wl->rng_initialized = 1;
 	err = hwrng_register(&wl->rng);
 	if (err) {

Index: bu3sch-wireless-dev/drivers/char/hw_random/omap-rng.c
===================================================================
@@ -81,6 +81,7 @@ static struct hwrng omap_rng_ops = {
 	.name		= "omap",
 	.data_present	= omap_rng_data_present,
 	.data_read	= omap_rng_data_read,
+	.type		= HWRNG_TYPE_ONBOARD,
 };
 
 static int __init omap_rng_probe(struct platform_device *pdev)