fs: fix generic save command implementation

Fix a few issues with the generic "save" shell command, and fs_write()
function.

1) fstypes[].write wasn't filled in for some file-systems, and isn't
   checked when used, which could cause crashes/... if executing save
   on e.g. fat/ext filesystems.

2) fs_write() requires the length argument to be non-zero, since it needs
   to know exactly how many bytes to write. Adjust the comments and code
   according to this.

3) fs_write() wasn't prototyped in <fs.h> like other generic functions;
   other code should be able to call this directly rather than invoking
   the "save" shell command.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Simon Glass <sjg@chromium.org>

1 files changed, 3 insertions, 6 deletions

diff --git a/fs/fs.c b/fs/fs.c
index be1855d1291..9c2ef6b6597 100644
--- a/fs/fs.c
+++ b/fs/fs.c
@@ -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;
 	}