UBI: allow direct user-space I/O

Introduce a new ioctl UBI_IOCSETPROP to set properties
on a volume. Also add the first property:
UBI_PROP_DIRECT_WRITE, this property is used to set the
ability to use direct writes in userspace

Signed-off-by: Sidney Amani <seed@uffs.org>
Signed-off-by: Corentin Chary <corentincj@iksaif.net>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

4 files changed, 66 insertions, 19 deletions

diff --git a/drivers/mtd/ubi/Kconfig.debug b/drivers/mtd/ubi/Kconfig.debug
index 1e2ee22edeff..2246f154e2f7 100644
--- a/drivers/mtd/ubi/Kconfig.debug
+++ b/drivers/mtd/ubi/Kconfig.debug
@@ -33,16 +33,6 @@ config MTD_UBI_DEBUG_DISABLE_BGT
           This option switches the background thread off by default. The thread
           may be also be enabled/disabled via UBI sysfs.
 
-config MTD_UBI_DEBUG_USERSPACE_IO
-        bool "Direct user-space write/erase support"
-        default n
-        depends on MTD_UBI_DEBUG
-        help
-          By default, users cannot directly write and erase individual
-          eraseblocks of dynamic volumes, and have to use update operation
-          instead. This option enables this capability - it is very useful for
-          debugging and testing.
-
 config MTD_UBI_DEBUG_EMULATE_BITFLIPS
         bool "Emulate flash bit-flips"
         depends on MTD_UBI_DEBUG
diff --git a/drivers/mtd/ubi/cdev.c b/drivers/mtd/ubi/cdev.c
index f9631eb3fef3..e63c8fc3df3a 100644
--- a/drivers/mtd/ubi/cdev.c
+++ b/drivers/mtd/ubi/cdev.c
@@ -259,12 +259,9 @@ static ssize_t vol_cdev_read(struct file *file, __user char *buf, size_t count,
         return err ? err : count_save - count;
 }
 
-#ifdef CONFIG_MTD_UBI_DEBUG_USERSPACE_IO
-
 /*
  * This function allows to directly write to dynamic UBI volumes, without
- * issuing the volume update operation. Available only as a debugging feature.
- * Very useful for testing UBI.
+ * issuing the volume update operation.
  */
 static ssize_t vol_cdev_direct_write(struct file *file, const char __user *buf,
                                      size_t count, loff_t *offp)
@@ -276,6 +273,9 @@ static ssize_t vol_cdev_direct_write(struct file *file, const char __user *buf,
         size_t count_save = count;
         char *tbuf;
 
+        if (!vol->direct_writes)
+                return -EPERM;
+
         dbg_gen("requested: write %zd bytes to offset %lld of volume %u",
                 count, *offp, vol->vol_id);
 
@@ -339,10 +339,6 @@ static ssize_t vol_cdev_direct_write(struct file *file, const char __user *buf,
         return err ? err : count_save - count;
 }
 
-#else
-#define vol_cdev_direct_write(file, buf, count, offp) (-EPERM)
-#endif /* CONFIG_MTD_UBI_DEBUG_USERSPACE_IO */
-
 static ssize_t vol_cdev_write(struct file *file, const char __user *buf,
                               size_t count, loff_t *offp)
 {
@@ -552,6 +548,30 @@ static long vol_cdev_ioctl(struct file *file, unsigned int cmd,
                 break;
         }
 
+        /* Set volume property command*/
+        case UBI_IOCSETPROP:
+        {
+                struct ubi_set_prop_req req;
+
+                err = copy_from_user(&req, argp,
+                                sizeof(struct ubi_set_prop_req));
+                if (err) {
+                        err = -EFAULT;
+                        break;
+                }
+                switch (req.property) {
+                case UBI_PROP_DIRECT_WRITE:
+                        mutex_lock(&ubi->volumes_mutex);
+                        desc->vol->direct_writes = !!req.value;
+                        mutex_unlock(&ubi->volumes_mutex);
+                        break;
+                default:
+                        err = -EINVAL;
+                        break;
+                }
+                break;
+        }
+
         default:
                 err = -ENOTTY;
                 break;
diff --git a/drivers/mtd/ubi/ubi.h b/drivers/mtd/ubi/ubi.h
index 381f0e1d0a74..c055511bb1b2 100644
--- a/drivers/mtd/ubi/ubi.h
+++ b/drivers/mtd/ubi/ubi.h
@@ -206,6 +206,7 @@ struct ubi_volume_desc;
  * @upd_marker: %1 if the update marker is set for this volume
  * @updating: %1 if the volume is being updated
  * @changing_leb: %1 if the atomic LEB change ioctl command is in progress
+ * @direct_writes: %1 if direct writes are enabled for this volume
  *
  * @gluebi_desc: gluebi UBI volume descriptor
  * @gluebi_refcount: reference count of the gluebi MTD device
@@ -253,6 +254,7 @@ struct ubi_volume {
         unsigned int upd_marker:1;
         unsigned int updating:1;
         unsigned int changing_leb:1;
+        unsigned int direct_writes:1;
 
 #ifdef CONFIG_MTD_UBI_GLUEBI
         /*
@@ -304,7 +306,8 @@ struct ubi_wl_entry;
  * @vtbl_size: size of the volume table in bytes
  * @vtbl: in-RAM volume table copy
  * @volumes_mutex: protects on-flash volume table and serializes volume
- *                 changes, like creation, deletion, update, re-size and re-name
+ *                 changes, like creation, deletion, update, re-size,
+ *                 re-name and set property
  *
  * @max_ec: current highest erase counter value
  * @mean_ec: current mean erase counter value
diff --git a/include/mtd/ubi-user.h b/include/mtd/ubi-user.h
index 82113e160a2c..296efae3525e 100644
--- a/include/mtd/ubi-user.h
+++ b/include/mtd/ubi-user.h
@@ -124,6 +124,14 @@
  * To check if a logical eraseblock is mapped to a physical eraseblock, the
  * %UBI_IOCEBISMAP ioctl command should be used. It returns %0 if the LEB is
  * not mapped, and %1 if it is mapped.
+ *
+ * Set an UBI volume property
+ * ~~~~~~~~~~~~~~~~~~~~~~~~~
+ *
+ * To set an UBI volume property the %UBI_IOCSETPROP ioctl command should be
+ * used. A pointer to a &struct ubi_set_prop_req object is expected to be
+ * passed. The object describes which property should be set, and to which value
+ * it should be set.
  */
 
 /*
@@ -175,6 +183,8 @@
 #define UBI_IOCEBUNMAP _IOW(UBI_VOL_IOC_MAGIC, 4, int32_t)
 /* Check if LEB is mapped command */
 #define UBI_IOCEBISMAP _IOR(UBI_VOL_IOC_MAGIC, 5, int32_t)
+/* Set an UBI volume property */
+#define UBI_IOCSETPROP _IOW(UBI_VOL_IOC_MAGIC, 6, struct ubi_set_prop_req)
 
 /* Maximum MTD device name length supported by UBI */
 #define MAX_UBI_MTD_NAME_LEN 127
@@ -210,6 +220,16 @@ enum {
         UBI_STATIC_VOLUME  = 4,
 };
 
+/*
+ * UBI set property ioctl constants
+ *
+ * @UBI_PROP_DIRECT_WRITE: allow / disallow user to directly write and
+ *                         erase individual eraseblocks on dynamic volumes
+ */
+enum {
+       UBI_PROP_DIRECT_WRITE = 1,
+};
+
 /**
  * struct ubi_attach_req - attach MTD device request.
  * @ubi_num: UBI device number to create
@@ -373,4 +393,18 @@ struct ubi_map_req {
         int8_t  padding[3];
 } __attribute__ ((packed));
 
+
+/**
+ * struct ubi_set_prop_req - a data structure used to set an ubi volume
+ *                           property.
+ * @property: property to set (%UBI_PROP_DIRECT_WRITE)
+ * @padding: reserved for future, not used, has to be zeroed
+ * @value: value to set
+ */
+struct ubi_set_prop_req {
+       uint8_t  property;
+       uint8_t  padding[7];
+       uint64_t value;
+}  __attribute__ ((packed));
+
 #endif /* __UBI_USER_H__ */