fs: fix generic save command implementation

index be1855d1291f..9c2ef6b6597c 100644
@@ -75,6 +75,7 @@ static struct fstype_info fstypes[] = {
 		.close = fat_close,
 		.ls = file_fat_ls,
 		.read = fat_read_file,
+		.write = fs_write_unsupported,
 	},
 #endif
 #ifdef CONFIG_FS_EXT4

@@ -84,6 +85,7 @@ static struct fstype_info fstypes[] = {
 		.close = ext4fs_close,
 		.ls = ext4fs_ls,
 		.read = ext4_read_file,
+		.write = fs_write_unsupported,
 	},
 #endif
 #ifdef CONFIG_SANDBOX

@@ -212,16 +214,11 @@ int fs_write(const char *filename, ulong addr, int offset, int len)
 	void *buf;
 	int ret;
 
-	/*
-	 * We don't actually know how many bytes are being read, since len==0
-	 * means read the whole file.
-	 */
 	buf = map_sysmem(addr, len);
 	ret = info->write(filename, buf, offset, len);
 	unmap_sysmem(buf);
 
-	/* If we requested a specific number of bytes, check we got it */
-	if (ret >= 0 && len && ret != len) {
+	if (ret >= 0 && ret != len) {
 		printf("** Unable to write file %s **\n", filename);
 		ret = -1;
 	}

index 7d9403ed8758..97b0094e954b 100644
@@ -55,6 +55,16 @@ int fs_ls(const char *dirname);
 int fs_read(const char *filename, ulong addr, int offset, int len);
 
 /*
+ * Write file "filename" to the partition previously set by fs_set_blk_dev(),
+ * from address "addr", starting at byte offset "offset", and writing "len"
+ * bytes. "offset" may be 0 to write to the start of the file. Note that not
+ * all filesystem types support offset!=0.
+ *
+ * Returns number of bytes read on success. Returns <= 0 on error.
+ */
+int fs_write(const char *filename, ulong addr, int offset, int len);
+
+/*
  * Common implementation for various filesystem commands, optionally limited
  * to a specific filesystem type via the fstype parameter.
  */

index 91a205ac1e69..44b00cd125b7 100644
@@ -49,3 +49,17 @@ U_BOOT_CMD(
 	"    - List files in directory 'directory' of partition 'part' on\n"
 	"      device type 'interface' instance 'dev'."
 );
+
+int do_exists_wrapper(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
+{
+	return do_exists(cmdtp, flag, argc, argv, FS_TYPE_ANY);
+}
+
+U_BOOT_CMD(
+	exists,	4,	0,	do_exists_wrapper,
+	"determine whether a file exists",
+	"<interface> <dev[:part]> filename\n"
+	"    - Determine whether 'filename' exists in partition 'part' on\n"
+	"      device type 'interface' instance 'dev', and set the command.\n"
+	"      exit status so that 'if exists ...; then' works.\n"
+);

index 9c2ef6b6597c..f3d9a1c6bc7d 100644
@@ -41,6 +41,11 @@ static inline int fs_ls_unsupported(const char *dirname)
 	return -1;
 }
 
+static inline int fs_exists_unsupported(const char *filename)
+{
+	return -1;
+}
+
 static inline int fs_read_unsupported(const char *filename, void *buf,
 				      int offset, int len)
 {

@@ -62,6 +67,7 @@ struct fstype_info {
 	int (*probe)(block_dev_desc_t *fs_dev_desc,
 		     disk_partition_t *fs_partition);
 	int (*ls)(const char *dirname);
+	int (*exists)(const char *filename);
 	int (*read)(const char *filename, void *buf, int offset, int len);
 	int (*write)(const char *filename, void *buf, int offset, int len);
 	void (*close)(void);

@@ -74,6 +80,7 @@ static struct fstype_info fstypes[] = {
 		.probe = fat_set_blk_dev,
 		.close = fat_close,
 		.ls = file_fat_ls,
+		.exists = fs_exists_unsupported,
 		.read = fat_read_file,
 		.write = fs_write_unsupported,
 	},

@@ -84,6 +91,7 @@ static struct fstype_info fstypes[] = {
 		.probe = ext4fs_probe,
 		.close = ext4fs_close,
 		.ls = ext4fs_ls,
+		.exists = fs_exists_unsupported,
 		.read = ext4_read_file,
 		.write = fs_write_unsupported,
 	},

@@ -94,6 +102,7 @@ static struct fstype_info fstypes[] = {
 		.probe = sandbox_fs_set_blk_dev,
 		.close = sandbox_fs_close,
 		.ls = sandbox_fs_ls,
+		.exists = fs_exists_unsupported,
 		.read = fs_read_sandbox,
 		.write = fs_write_sandbox,
 	},

@@ -103,6 +112,7 @@ static struct fstype_info fstypes[] = {
 		.probe = fs_probe_unsupported,
 		.close = fs_close_unsupported,
 		.ls = fs_ls_unsupported,
+		.exists = fs_exists_unsupported,
 		.read = fs_read_unsupported,
 		.write = fs_write_unsupported,
 	},

@@ -184,6 +194,19 @@ int fs_ls(const char *dirname)
 	return ret;
 }
 
+int fs_exists(const char *filename)
+{
+	int ret;
+
+	struct fstype_info *info = fs_get_info(fs_type);
+
+	ret = info->exists(filename);
+
+	fs_close();
+
+	return ret;
+}
+
 int fs_read(const char *filename, ulong addr, int offset, int len)
 {
 	struct fstype_info *info = fs_get_info(fs_type);

@@ -309,6 +332,21 @@ int do_ls(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[],
 	return 0;
 }
 
+int do_exists(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[],
+		int fstype)
+{
+	if (argc != 4)
+		return CMD_RET_USAGE;
+
+	if (fs_set_blk_dev(argv[1], argv[2], fstype))
+		return 1;
+
+	if (fs_exists(argv[3]))
+		return 1;
+
+	return 0;
+}
+
 int do_save(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[],
 		int fstype)
 {

index 97b0094e954b..b8b7706410ad 100644
@@ -44,6 +44,14 @@ int fs_set_blk_dev(const char *ifname, const char *dev_part_str, int fstype);
 int fs_ls(const char *dirname);
 
 /*
+ * Determine whether a file exists
+ *
+ * Returns 0 if the file exists, non-zero if it doesn't exist.
+ * This encoding was picked to help shell command implementation.
+ */
+int fs_exists(const char *filename);
+
+/*
  * Read file "filename" from the partition previously set by fs_set_blk_dev(),
  * to address "addr", starting at byte offset "offset", and reading "len"
  * bytes. "offset" may be 0 to read from the start of the file. "len" may be

@@ -72,6 +80,8 @@ int do_load(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[],
 		int fstype);
 int do_ls(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[],
 		int fstype);
+int do_exists(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[],
+		int fstype);
 int do_save(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[],
 		int fstype);
 

index 00982b164dd3..c8d36b747d6a 100644
@@ -22,6 +22,12 @@ static int do_sandbox_ls(cmd_tbl_t *cmdtp, int flag, int argc,
 	return do_ls(cmdtp, flag, argc, argv, FS_TYPE_SANDBOX);
 }
 
+static int do_sandbox_exists(cmd_tbl_t *cmdtp, int flag, int argc,
+			     char * const argv[])
+{
+	return do_exists(cmdtp, flag, argc, argv, FS_TYPE_SANDBOX);
+}
+
 static int do_sandbox_save(cmd_tbl_t *cmdtp, int flag, int argc,
 			   char * const argv[])
 {

@@ -88,6 +94,7 @@ static int do_sandbox_info(cmd_tbl_t *cmdtp, int flag, int argc,
 static cmd_tbl_t cmd_sandbox_sub[] = {
 	U_BOOT_CMD_MKENT(load, 7, 0, do_sandbox_load, "", ""),
 	U_BOOT_CMD_MKENT(ls, 3, 0, do_sandbox_ls, "", ""),
+	U_BOOT_CMD_MKENT(exists, 3, 0, do_sandbox_exists, "", ""),
 	U_BOOT_CMD_MKENT(save, 6, 0, do_sandbox_save, "", ""),
 	U_BOOT_CMD_MKENT(bind, 3, 0, do_sandbox_bind, "", ""),
 	U_BOOT_CMD_MKENT(info, 3, 0, do_sandbox_info, "", ""),

index f3d9a1c6bc7d..4f344c6d6d72 100644
@@ -102,7 +102,7 @@ static struct fstype_info fstypes[] = {
 		.probe = sandbox_fs_set_blk_dev,
 		.close = sandbox_fs_close,
 		.ls = sandbox_fs_ls,
-		.exists = fs_exists_unsupported,
+		.exists = sandbox_fs_exists,
 		.read = fs_read_sandbox,
 		.write = fs_write_sandbox,
 	},

index dd028da8e32b..7940c93dc6a3 100644
@@ -72,6 +72,14 @@ int sandbox_fs_ls(const char *dirname)
 	return 0;
 }
 
+int sandbox_fs_exists(const char *filename)
+{
+	ssize_t sz;
+
+	sz = os_get_filesize(filename);
+	return (sz >= 0) ? 0 : -1;
+}
+
 void sandbox_fs_close(void)
 {
 }

index 8ea8cb7e2e62..a51ad13044e1 100644
@@ -25,6 +25,7 @@ long sandbox_fs_read_at(const char *filename, unsigned long pos,
 
 void sandbox_fs_close(void);
 int sandbox_fs_ls(const char *dirname);
+int sandbox_fs_exists(const char *filename);
 int fs_read_sandbox(const char *filename, void *buf, int offset, int len);
 int fs_write_sandbox(const char *filename, void *buf, int offset, int len);
 

index 735b2564175b..71ecdd8e9a31 100644
@@ -174,6 +174,14 @@ int ext4fs_ls(const char *dirname)
 	return 0;
 }
 
+int ext4fs_exists(const char *filename)
+{
+	int file_len;
+
+	file_len = ext4fs_open(filename);
+	return (file_len >= 0) ? 0 : 1;
+}
+
 int ext4fs_read(char *buf, unsigned len)
 {
 	if (ext4fs_root == NULL || ext4fs_file == NULL)

index 4f344c6d6d72..3f14d0169b43 100644
@@ -91,7 +91,7 @@ static struct fstype_info fstypes[] = {
 		.probe = ext4fs_probe,
 		.close = ext4fs_close,
 		.ls = ext4fs_ls,
-		.exists = fs_exists_unsupported,
+		.exists = ext4fs_exists,
 		.read = ext4_read_file,
 		.write = fs_write_unsupported,
 	},

index 242938039662..aacb147de24b 100644
@@ -134,6 +134,7 @@ int ext4fs_read(char *buf, unsigned len);
 int ext4fs_mount(unsigned part_length);
 void ext4fs_close(void);
 int ext4fs_ls(const char *dirname);
+int ext4fs_exists(const char *filename);
 void ext4fs_free_node(struct ext2fs_node *node, struct ext2fs_node *currroot);
 int ext4fs_devread(lbaint_t sector, int byte_offset, int byte_len, char *buf);
 void ext4fs_set_blk_dev(block_dev_desc_t *rbdd, disk_partition_t *info);

index b41d62e3c386..bc06c0a3c688 100644
@@ -808,7 +808,7 @@ __u8 do_fat_read_at_block[MAX_CLUSTSIZE]
 
 long
 do_fat_read_at(const char *filename, unsigned long pos, void *buffer,
-	       unsigned long maxsize, int dols)
+	       unsigned long maxsize, int dols, int dogetsize)
 {
 	char fnamecopy[2048];
 	boot_sector bs;

@@ -1152,7 +1152,10 @@ rootdir_done:
 			subname = nextname;
 	}
 
-	ret = get_contents(mydata, dentptr, pos, buffer, maxsize);
+	if (dogetsize)
+		ret = FAT2CPU32(dentptr->size);
+	else
+		ret = get_contents(mydata, dentptr, pos, buffer, maxsize);
 	debug("Size: %d, got: %ld\n", FAT2CPU32(dentptr->size), ret);
 
 exit:

@@ -1163,7 +1166,7 @@ exit:
 long
 do_fat_read(const char *filename, void *buffer, unsigned long maxsize, int dols)
 {
-	return do_fat_read_at(filename, 0, buffer, maxsize, dols);
+	return do_fat_read_at(filename, 0, buffer, maxsize, dols, 0);
 }
 
 int file_fat_detectfs(void)

@@ -1233,11 +1236,18 @@ int file_fat_ls(const char *dir)
 	return do_fat_read(dir, NULL, 0, LS_YES);
 }
 
+int fat_exists(const char *filename)
+{
+	int sz;
+	sz = do_fat_read_at(filename, 0, NULL, 0, LS_NO, 1);
+	return (sz >= 0) ? 0 : 1;
+}
+
 long file_fat_read_at(const char *filename, unsigned long pos, void *buffer,
 		      unsigned long maxsize)
 {
 	printf("reading %s\n", filename);
-	return do_fat_read_at(filename, pos, buffer, maxsize, LS_NO);
+	return do_fat_read_at(filename, pos, buffer, maxsize, LS_NO, 0);
 }
 
 long file_fat_read(const char *filename, void *buffer, unsigned long maxsize)

index 3f14d0169b43..d2bc8d0f1459 100644
@@ -80,7 +80,7 @@ static struct fstype_info fstypes[] = {
 		.probe = fat_set_blk_dev,
 		.close = fat_close,
 		.ls = file_fat_ls,
-		.exists = fs_exists_unsupported,
+		.exists = fat_exists,
 		.read = fat_read_file,
 		.write = fs_write_unsupported,
 	},

index 2c951e7d79c6..c8eb7ccd2904 100644
@@ -188,6 +188,7 @@ file_read_func		file_fat_read;
 int file_cd(const char *path);
 int file_fat_detectfs(void);
 int file_fat_ls(const char *dir);
+int fat_exists(const char *filename);
 long file_fat_read_at(const char *filename, unsigned long pos, void *buffer,
 		      unsigned long maxsize);
 long file_fat_read(const char *filename, void *buffer, unsigned long maxsize);