tools/env: allow negative offsets

A negative value for the offset is treated as a backwards offset for
from the end of the device/partition for block devices. This aligns
the behavior of the config file with the syntax of CONFIG_ENV_OFFSET
where the functionality has been introduced with
commit 5c088ee841f9 ("env_mmc: allow negative CONFIG_ENV_OFFSET").

Signed-off-by: Stefan Agner <stefan.agner@toradex.com>

diff --git a/tools/env/fw_env.c b/tools/env/fw_env.c
index 06d6865f3b30eb41318983eb45610a35a471e9b3..be338a5ba909dcbada9bc746457e7fa3936e513b 100644 (file)
--- a/tools/env/fw_env.c
+++ b/tools/env/fw_env.c
@@ -14,6 +14,7 @@
 #include <errno.h>
 #include <env_flags.h>
 #include <fcntl.h>
+#include <linux/fs.h>
 #include <linux/stringify.h>
 #include <ctype.h>
 #include <stdio.h>
@@ -51,7 +52,7 @@ struct env_opts default_opts = {
 
 struct envdev_s {
        const char *devname;            /* Device name */
-       ulong devoff;                   /* Device offset */
+       long long devoff;               /* Device offset */
        ulong env_size;                 /* environment size */
        ulong erase_size;               /* device erase size */
        ulong env_sectors;              /* number of environment sectors */
@@ -994,7 +995,7 @@ static int flash_write (int fd_current, int fd_target, int dev_target)
        }
 
 #ifdef DEBUG
-       fprintf(stderr, "Writing new environment at 0x%lx on %s\n",
+       fprintf(stderr, "Writing new environment at 0x%llx on %s\n",
                DEVOFFSET (dev_target), DEVNAME (dev_target));
 #endif
 
@@ -1010,7 +1011,7 @@ static int flash_write (int fd_current, int fd_target, int dev_target)
                        offsetof (struct env_image_redundant, flags);
 #ifdef DEBUG
                fprintf(stderr,
-                       "Setting obsolete flag in environment at 0x%lx on %s\n",
+                       "Setting obsolete flag in environment at 0x%llx on %s\n",
                        DEVOFFSET (dev_current), DEVNAME (dev_current));
 #endif
                flash_flag_obsolete (dev_current, fd_current, offset);
@@ -1335,7 +1336,27 @@ static int check_device_config(int dev)
                }
                DEVTYPE(dev) = mtdinfo.type;
        } else {
+               uint64_t size;
                DEVTYPE(dev) = MTD_ABSENT;
+
+               /*
+                * Check for negative offsets, treat it as backwards offset
+                * from the end of the block device
+                */
+               if (DEVOFFSET(dev) < 0) {
+                       rc = ioctl(fd, BLKGETSIZE64, &size);
+                       if (rc < 0) {
+                               fprintf(stderr, "Could not get block device size on %s\n",
+                                       DEVNAME(dev));
+                               goto err;
+                       }
+
+                       DEVOFFSET(dev) = DEVOFFSET(dev) + size;
+#ifdef DEBUG
+                       fprintf(stderr, "Calculated device offset 0x%llx on %s\n",
+                               DEVOFFSET(dev), DEVNAME(dev));
+#endif
+               }
        }
 
 err:
@@ -1434,12 +1455,12 @@ static int get_config (char *fname)
                if (dump[0] == '#')
                        continue;
 
-               rc = sscanf (dump, "%ms %lx %lx %lx %lx",
-                            &devname,
-                            &DEVOFFSET (i),
-                            &ENVSIZE (i),
-                            &DEVESIZE (i),
-                            &ENVSECTORS (i));
+               rc = sscanf(dump, "%ms %lli %lx %lx %lx",
+                           &devname,
+                           &DEVOFFSET(i),
+                           &ENVSIZE(i),
+                           &DEVESIZE(i),
+                           &ENVSECTORS(i));
 
                if (rc < 3)
                        continue;

diff --git a/tools/env/fw_env.config b/tools/env/fw_env.config
index 776e16f784c59934c29b42237bacc80c9ab60a68..7916ebdb1f6d1836c49d9374cf4ebfac2bcf0009 100644 (file)
--- a/tools/env/fw_env.config
+++ b/tools/env/fw_env.config
@@ -4,6 +4,7 @@
 # Notice, that the "Number of sectors" is not required on NOR and SPI-dataflash.
 # Futhermore, if the Flash sector size is omitted, this value is assumed to
 # be the same as the Environment size, which is valid for NOR and SPI-dataflash
+# Device offset must be prefixed with 0x to be parsed as a hexadecimal value.
 
 # NOR example
 # MTD device name      Device offset   Env. size       Flash sector size       Number of sectors
@@ -18,8 +19,12 @@
 # NAND example
 #/dev/mtd0             0x4000          0x4000          0x20000                 2
 
+# On a block device a negative offset is treated as a backwards offset from the
+# end of the device/partition, rather than a forwards offset from the start.
+
 # Block device example
 #/dev/mmcblk0          0xc0000         0x20000
+#/dev/mmcblk0          -0x20000        0x20000
 
 # VFAT example
 #/boot/uboot.env       0x0000          0x4000