Implement MMC password force erase, remove password, change password,
unlock card and assign password operations. It uses the sysfs mechanism
to send commands to the MMC subsystem. 

Signed-off-by: Carlos Eduardo Aguiar <carlos.aguiar@indt.org.br>
Signed-off-by: Anderson Lizardo <anderson.lizardo@indt.org.br>
Signed-off-by: Anderson Briglia <anderson.briglia@indt.org.br>

Index: linux-linus-2.6/drivers/mmc/mmc_sysfs.c
===================================================================
--- linux-linus-2.6.orig/drivers/mmc/mmc_sysfs.c	2007-01-03 07:57:40.000000000 -0400
+++ linux-linus-2.6/drivers/mmc/mmc_sysfs.c	2007-01-03 07:58:14.000000000 -0400
@@ -17,6 +17,7 @@
 #include <linux/idr.h>
 #include <linux/workqueue.h>
 #include <linux/key.h>
+#include <linux/err.h>
 
 #include <linux/mmc/card.h>
 #include <linux/mmc/host.h>
@@ -65,6 +66,107 @@ static struct device_attribute mmc_dev_a
 
 static struct device_attribute mmc_dev_attr_scr = MMC_ATTR_RO(scr);
 
+#ifdef	CONFIG_MMC_PASSWORDS
+
+static ssize_t
+mmc_lockable_show(struct device *dev, struct device_attribute *att, char *buf)
+{
+	struct mmc_card *card = dev_to_mmc_card(dev);
+
+	if (!mmc_card_lockable(card))
+		return sprintf(buf, "unsupported\n");
+	else
+		return sprintf(buf, "%slocked\n", mmc_card_locked(card) ?
+			"" : "un");
+}
+
+/*
+ * implement MMC password functions: force erase, remove password, change
+ * password, unlock card and assign password.
+ */
+static ssize_t
+mmc_lockable_store(struct device *dev, struct device_attribute *att,
+	const char *data, size_t len)
+{
+	struct mmc_card *card = dev_to_mmc_card(dev);
+	int err;
+
+	err = mmc_card_claim_host(card);
+	if (err != MMC_ERR_NONE)
+		return -EINVAL;
+
+	err = mmc_card_lockable(card);
+	if (!err)
+		goto error;
+
+	if (mmc_card_locked(card) && !strncmp(data, "erase", 5)) {
+		/* forced erase only works while card is locked */
+		mmc_lock_unlock(card, NULL, MMC_LOCK_MODE_ERASE);
+		goto out;
+	} else if (!mmc_card_locked(card) && !strncmp(data, "remove", 6)) {
+		/* remove password only works while card is unlocked */
+		struct key *mmc_key = request_key(&mmc_key_type, "mmc:key", "remove");
+
+		if (!IS_ERR(mmc_key)) {
+			int err =  mmc_lock_unlock(card, mmc_key, MMC_LOCK_MODE_CLR_PWD);
+			if (!err)
+				goto out;
+		} else
+			goto request_key_error;
+	} else if (!mmc_card_locked(card) && ((!strncmp(data, "assign", 6)) ||
+					      (!strncmp(data, "change", 6)))) {
+
+			/* assign or change */
+			struct key *mmc_key;
+
+			if(!strncmp(data, "assign", 6))
+				mmc_key = request_key(&mmc_key_type, "mmc:key", "assign");
+			else
+				mmc_key = request_key(&mmc_key_type, "mmc:key", "change");
+
+			if (!IS_ERR(mmc_key)) {
+				int err =  mmc_lock_unlock(card, mmc_key, MMC_LOCK_MODE_SET_PWD);
+				if (!err)
+					goto out;
+			} else
+				goto request_key_error;
+	} else if (mmc_card_locked(card) && !strncmp(data, "unlock", 6)) {
+			/* unlock */
+			struct key *mmc_key = request_key(&mmc_key_type, "mmc:key", "unlock");
+			if (!IS_ERR(mmc_key)) {
+				int err = mmc_lock_unlock(card, mmc_key, MMC_LOCK_MODE_UNLOCK);
+				if (err) {
+					dev_dbg(&card->dev, "Wrong password\n");
+					goto error;
+				}
+				else {
+					mmc_card_release_host(card);
+					goto out_unlocked;
+				}
+			} else
+				goto request_key_error;
+	}
+
+request_key_error:
+	dev_dbg(&card->dev, "request_key returned error %ld\n", PTR_ERR(mmc_key));
+error:
+	mmc_card_release_host(card);
+	return -EINVAL;
+out:
+	mmc_card_release_host(card);
+	return len;
+
+out_unlocked:
+	device_release_driver(dev);
+	device_attach(dev);
+	return len;
+}
+
+static struct device_attribute mmc_dev_attr_lockable =
+	__ATTR(lockable, S_IWUSR | S_IRUGO,
+		 mmc_lockable_show, mmc_lockable_store);
+
+#endif
 
 static void mmc_release_card(struct device *dev)
 {
@@ -234,6 +336,11 @@ int mmc_register_card(struct mmc_card *c
 			if (ret)
 				device_del(&card->dev);
 		}
+#ifdef CONFIG_MMC_PASSWORDS
+		ret = device_create_file(&card->dev, &mmc_dev_attr_lockable);
+		if (ret)
+			device_del(&card->dev);
+#endif
 	}
 	return ret;
 }
@@ -248,6 +355,9 @@ void mmc_remove_card(struct mmc_card *ca
 		if (mmc_card_sd(card))
 			device_remove_file(&card->dev, &mmc_dev_attr_scr);
 
+#ifdef CONFIG_MMC_PASSWORDS
+		device_remove_file(&card->dev, &mmc_dev_attr_lockable);
+#endif
 		device_del(&card->dev);
 	}