[U-Boot] [PATCH 4/4] [v3] cmd_nand: add nand write.trimffs command

[Ben Gardiner]

Add another nand write. variant, trimffs. This command will request of
nand_write_skip_bad() that all trailing all-0xff pages will be
dropped from eraseblocks when they are written to flash as-per the
reccommended behaviour of the UBI FAQ [1].

The function that implements this timming is the drop_ffs() function
by Artem Bityutskiy, ported from the mtd-utils tree.

[1] http://www.linux-mtd.infradead.org/doc/ubi.html#L_flasher_algo

Signed-off-by: Ben Gardiner <bengardiner at nanometrics.ca>
CC: Artem Bityutskiy <dedekind1 at gmail.com>
CC: Detlev Zundel <dzu at denx.de>

---

Changes since v2:
 * added nand write.trimffs to the README.nand file
 * moved the nand_util copyright header addition to patch 'nand_util:
   drop trailing all-0xff pages if requested'
Changes since v1:
 * rebased to HEAD of git://git.denx.de/u-boot-nand-flash.git : ff7b4a0
   ("env_nand: zero-initialize variable nand_erase_options")
 * renamed the command variant to '.trimffs' from '.ubi' (Detlev Zundel)
 * added attribution to mtd-utils and Artem Bityutskiy in both the source
   comments and commit message
 * wrapped the new command in a new ifdef, CONFIG_CMD_NAND_TRIMFFS, to
   reduce the size impact of this new feature
---
 common/cmd_nand.c |   16 ++++++++++++++++
 doc/README.nand   |   10 ++++++++++
 2 files changed, 26 insertions(+), 0 deletions(-)

diff --git a/common/cmd_nand.c b/common/cmd_nand.c
index e7db4c9..786f179 100644
--- a/common/cmd_nand.c
+++ b/common/cmd_nand.c
@@ -575,6 +575,16 @@ int do_nand(cmd_tbl_t * cmdtp, int flag, int argc, char * const argv[])
 			else
 				ret = nand_write_skip_bad(nand, off, &rwsize,
 							  (u_char *)addr, 0);
+#ifdef CONFIG_CMD_NAND_TRIMFFS
+		} else if (!strcmp(s, ".trimffs")) {
+			if (read) {
+				printf("Unknown nand command suffix '%s'\n", s);
+				return 1;
+			}
+			ret = nand_write_skip_bad(nand, off, &rwsize,
+						(u_char *)addr,
+						WITH_DROP_FFS);
+#endif
 #ifdef CONFIG_CMD_NAND_YAFFS
 		} else if (!strcmp(s, ".yaffs")) {
 			if (read) {
@@ -689,6 +699,12 @@ U_BOOT_CMD(
 	"nand write - addr off|partition size\n"
 	"    read/write 'size' bytes starting at offset 'off'\n"
 	"    to/from memory address 'addr', skipping bad blocks.\n"
+#ifdef CONFIG_CMD_NAND_TRIMFFS
+	"nand write.trimffs - addr off|partition size\n"
+	"    write 'size' bytes starting at offset 'off' from memory address\n"
+	"    'addr', skipping bad blocks and dropping any pages at the end\n"
+	"    of eraseblocks that contain only 0xFF\n"
+#endif
 #ifdef CONFIG_CMD_NAND_YAFFS
 	"nand write.yaffs - addr off|partition size\n"
 	"    write 'size' bytes starting at offset 'off' with yaffs format\n"
diff --git a/doc/README.nand b/doc/README.nand
index 8eedb6c..ca62f00 100644
--- a/doc/README.nand
+++ b/doc/README.nand
@@ -78,6 +78,16 @@ Commands:
       should work well, but loading an image copied from another flash is
       going to be trouble if there are any bad blocks.
 
+   nand write.trimffs addr ofs|partition size
+      Enabled by the CONFIG_CMD_NAND_TRIMFFS macro. This command will write to
+      the NAND flash in a manner identical to the 'nand write' command described
+      above -- with the additional check that all pages at the end of
+      eraseblocks which contain only 0xff data will not be written to the NAND
+      flash. This behaviour is required when flashing UBI images containing
+       UBIFS volumes as per the UBI FAQ[1].
+
+      [1] http://www.linux-mtd.infradead.org/doc/ubi.html#L_flasher_algo
+
    nand write.oob addr ofs|partition size
       Write `size' bytes from `addr' to the out-of-band data area
       corresponding to `ofs' in NAND flash. This is limited to the 16 bytes
-- 
1.7.4.1