flashrom.c: allow - as filename for stdin

Allows - as filename for -w/-v options. It is sometimes useful to
script flashrom and allowing it to work with pipes allows for more
flexibility in this specific use-case.

Signed-off-by: Daniel Campello <campello@chromium.org>
Change-Id: I97889cfdf7ba9a257e182c4ee2b20075cfa58d4d
Original-Reviewed-on: https://review.coreboot.org/c/flashrom/+/52383
Original-Reviewed-by: Edward O'Callaghan <quasisec@chromium.org>
diff --git a/flashrom.c b/flashrom.c
index b48f860..9b9c2fc 100644
--- a/flashrom.c
+++ b/flashrom.c
@@ -1294,7 +1294,11 @@
 	int ret = 0;
 
 	FILE *image;
-	if ((image = fopen(filename, "rb")) == NULL) {
+	if (!strcmp(filename, "-"))
+		image = fdopen(fileno(stdin), "rb");
+	else
+		image = fopen(filename, "rb");
+	if (image == NULL) {
 		msg_gerr("Error: opening file \"%s\" failed: %s\n", filename, strerror(errno));
 		return 1;
 	}
@@ -1305,7 +1309,7 @@
 		ret = 1;
 		goto out;
 	}
-	if (image_stat.st_size != (intmax_t)size) {
+	if ((image_stat.st_size != (intmax_t)size) && strcmp(filename, "-")) {
 		msg_gerr("Error: Image size (%jd B) doesn't match the flash chip's size (%lu B)!\n",
 			 (intmax_t)image_stat.st_size, size);
 		ret = 1;