fw_env: autodetect NAND erase size and env sectors

As already done for NOR chips, if device ESIZE and ENVSECTORS static
configurations are both zero, then autodetect them at runtime.

Cc: Joe Hershberger <joe.hershberger@ni.com>
cc: Stefan Agner <stefan@agner.ch>
cc: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
Signed-off-by: Anthony Loiseau <anthony.loiseau@allcircuits.com>
diff --git a/tools/env/README b/tools/env/README
index 480a893..b8c6a7e 100644
--- a/tools/env/README
+++ b/tools/env/README
@@ -58,6 +58,9 @@
 this environment instance. On NAND this is used to limit the range
 within which bad blocks are skipped, on NOR it is not used.
 
+If DEVICEx_ESIZE and DEVICEx_ENVSECTORS are both zero, then a runtime
+detection is attempted for NOR and NAND mtd types.
+
 To prevent losing changes to the environment and to prevent confusing the MTD
 drivers, a lock file at /run/fw_printenv.lock is used to serialize access
 to the environment.
diff --git a/tools/env/fw_env.c b/tools/env/fw_env.c
index 90010da..74451ec 100644
--- a/tools/env/fw_env.c
+++ b/tools/env/fw_env.c
@@ -1652,8 +1652,15 @@
 		}
 		DEVTYPE(dev) = mtdinfo.type;
 		if (DEVESIZE(dev) == 0 && ENVSECTORS(dev) == 0 &&
-		    mtdinfo.type == MTD_NORFLASH)
-			DEVESIZE(dev) = mtdinfo.erasesize;
+		    mtdinfo.erasesize > 0) {
+			if (mtdinfo.type == MTD_NORFLASH)
+				DEVESIZE(dev) = mtdinfo.erasesize;
+			else if (mtdinfo.type == MTD_NANDFLASH) {
+				DEVESIZE(dev) = mtdinfo.erasesize;
+				ENVSECTORS(dev) =
+				    mtdinfo.size / mtdinfo.erasesize;
+			}
+		}
 		if (DEVESIZE(dev) == 0)
 			/* Assume the erase size is the same as the env-size */
 			DEVESIZE(dev) = ENVSIZE(dev);