common: Move get_dev_mtd() to mtd.c

Allows tests to link in alternative implementations of get_dev_mtd()
without losing other functions available in common.c.

Change-Id: I606a83aa9bc59b5fbab1fb11ee1e2574c7f6d127
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
diff --git a/mtd.c b/mtd.c
new file mode 100644
index 0000000..46d660e
--- /dev/null
+++ b/mtd.c
@@ -0,0 +1,43 @@
+#define _GNU_SOURCE
+#include <stdbool.h>
+#include <stdio.h>
+#include <string.h>
+
+#include "common.h"
+
+static bool is_pnor_part(const char *str)
+{
+	return strcasestr(str, "pnor") != NULL;
+}
+
+char *get_dev_mtd(void)
+{
+	FILE *f;
+	char *ret = NULL, *pos = NULL;
+	char line[255];
+
+	f = fopen("/proc/mtd", "r");
+	if (!f)
+		return NULL;
+
+	while (!pos && fgets(line, sizeof(line), f) != NULL) {
+		/* Going to have issues if we didn't get the full line */
+		if (line[strlen(line) - 1] != '\n')
+			break;
+
+		if (is_pnor_part(line)) {
+			pos = strchr(line, ':');
+			if (!pos)
+				break;
+		}
+	}
+	fclose(f);
+
+	if (pos) {
+		*pos = '\0';
+		if (asprintf(&ret, "/dev/%s", line) == -1)
+			ret = NULL;
+	}
+
+	return ret;
+}