[PATCH] flash_otp_write: fix writing to NAND in presence of partial reads

[Uwe Kleine-König]

When doing something like:

	{ printf "\xff"; printf "\xfe"; } | flash_otp_write -u /dev/mtd0 0

flash_otp_write might see only a single byte when reading from stdin for
the first tim. In this case (and without this patch) it pads to
$writesize with '\xff's and writes that out. In the next iteration it
reads the 2nd byte, pads and writes again. So the 2nd byte is written to
offset $writesize instead of 1.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig at pengutronix.de>
---
 flash_otp_write.c |   19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/flash_otp_write.c b/flash_otp_write.c
index 41cf1c5..0aa872e 100644
--- a/flash_otp_write.c
+++ b/flash_otp_write.c
@@ -15,6 +15,23 @@
 
 #include <mtd/mtd-user.h>
 
+ssize_t xread(int fd, void *buf, size_t count)
+{
+	ssize_t ret, done = 0;
+
+retry:
+	ret = read(fd, buf + done, count - done);
+	if (ret < 0)
+		return ret;
+
+	done += ret;
+
+	if (ret == 0 /* EOF */ || done == count)
+		return done;
+	else
+		goto retry;
+}
+
 int main(int argc,char *argv[])
 {
 	int fd, val, ret, size, wrote, len;
@@ -66,7 +83,7 @@ int main(int argc,char *argv[])
 		len = 256;
 
 	wrote = 0;
-	while ((size = read(0, buf, len))) {
+	while ((size = xread(0, buf, len))) {
 		if (size < 0) {
 			perror("read()");
 			return errno;
-- 
1.7.10.4