From: Javier Viguera <javier.viguera@digi.com>
Date: Fri, 15 Feb 2019 09:23:50 +0100
Subject: [PATCH 3/4] fw_env: add support to unlock emmc boot partition

Signed-off-by: Javier Viguera <javier.viguera@digi.com>
Signed-off-by: Arturo Buzarra <arturo.buzarra@digi.com>
---
 tools/env/fw_env.c | 39 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/tools/env/fw_env.c b/tools/env/fw_env.c
index ab06415898..5ebd7d6208 100644
--- a/tools/env/fw_env.c
+++ b/tools/env/fw_env.c
@@ -1052,13 +1052,42 @@ static int flash_read (int fd)
 		return -1;

 	return 0;
 }

+/*
+ * Set mmcboot partition read-write protection
+ */
+static int sysfs_mmcboot_set_protection(const char *device, int value)
+{
+	int fd;
+	ssize_t nbytes;
+	char buf[64];
+	snprintf(buf, sizeof(buf), "/sys/block/%s/force_ro", device);
+	fd = open(buf, O_WRONLY);
+	if (fd < 0) {
+		perror("sysfs_mmcboot_set_protection: error opening mmcblk");
+		return fd;
+	}
+	snprintf(buf, sizeof(buf), "%s", value ? "1" : "0");
+	nbytes = write(fd, buf, 2);
+	close(fd);
+
+	/* Verify bytes written */
+	if (nbytes < 2)
+	{
+		perror("sysfs_mmcboot_set_protection: error writing mmcblk protection");
+		return nbytes >=0 ? -EIO : nbytes;
+	}
+
+	return 0;
+}
+
 static int flash_io (int mode)
 {
 	int fd_current, fd_target, rc, dev_target;
+	char *mmcblk = NULL;

 	/* dev_current: fd_current, erase_current */
 	fd_current = open (DEVNAME (dev_current), mode);
 	if (fd_current < 0) {
 		fprintf (stderr,
@@ -1084,10 +1113,15 @@ static int flash_io (int mode)
 		} else {
 			dev_target = dev_current;
 			fd_target = fd_current;
 		}

+		/* Disable mmcboot protection if using EMMC (set read-write) */
+		mmcblk = strstr(DEVNAME(dev_target), "mmcblk");
+		if (mmcblk)
+			sysfs_mmcboot_set_protection(mmcblk, 0);
+
 		rc = flash_write (fd_current, fd_target, dev_target);

 		if (fsync(fd_current) &&
 		    !(errno == EINVAL || errno == EROFS)) {
 			fprintf (stderr,
@@ -1109,10 +1143,15 @@ static int flash_io (int mode)
 					DEVNAME (dev_target),
 					strerror (errno));
 				rc = -1;
 			}
 		}
+
+		/* Re-enable mmcboot protection (set read-only) */
+		if (mmcblk)
+			sysfs_mmcboot_set_protection(mmcblk, 1);
+
 	} else {
 		rc = flash_read (fd_current);
 	}

 exit: