Patchwork flash_otp_write: fix writing to NAND in presence of partial reads

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Submitter Uwe Kleine-König
Date Feb. 28, 2013, 9:42 a.m.
Message ID <1362044529-511-1-git-send-email-u.kleine-koenig@pengutronix.de>
Download mbox | patch
Permalink /patch/223856/
State New
Headers show

Comments

Uwe Kleine-König - Feb. 28, 2013, 9:42 a.m.
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@pengutronix.de>
---
 flash_otp_write.c |   19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)
Artem Bityutskiy - March 11, 2013, 7:51 a.m.
On Thu, 2013-02-28 at 10:42 +0100, Uwe Kleine-König wrote:
> 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@pengutronix.de>

Pushed both to mtd-utils.git, thanks!

Patch

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;