lib/boot_device: Add API for write protect a region

Add API that should be implemented by the boot media drivers
for write-protecting a subregion.

Change-Id: I4c9376e2c2c7a4852f13c65824c6cd64a1c6ac0a
Signed-off-by: Rizwan Qureshi <rizwan.qureshi@intel.com>
Reviewed-on: https://review.coreboot.org/c/28724
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Rudolph <siro@das-labor.org>

src/include/boot_device.h

@@ -18,6 +18,22 @@
 
 #include <commonlib/region.h>
 
+/*
+ * Boot device region can be protected by 2 sources, media and controller.
+ * The following modes are identified. It depends on the flash chip and the
+ * controller if mode is actually supported.
+ *
+ * MEDIA_WP : Flash/Boot device enforces write protect
+ * CTRLR_WP : Controller device enforces write protect
+ * CTRLR_RP : Controller device enforces read protect
+ * CTRLR_RWP : Controller device enforces read-write protect
+ */
+enum bootdev_prot_type {
+	CTRLR_WP = 1,
+	CTRLR_RP = 2,
+	CTRLR_RWP = 3,
+	MEDIA_WP = 4,
+};
 /*
  * Please note that the read-only boot device may not be coherent with
  * the read-write boot device. Thus, mixing mmap() and writeat() is
@@ -44,6 +60,14 @@ int boot_device_ro_subregion(const struct region *sub,
 int boot_device_rw_subregion(const struct region *sub,
 				struct region_device *subrd);
 
+/*
+ * Write protect a sub-region of the boot device represented
+ * by the region device.
+ * Returns 0 on success, < 0 on error.
+ */
+int boot_device_wp_region(struct region_device *rd,
+				const enum bootdev_prot_type type);
+
 /*
  * Initialize the boot device. This may be called multiple times within
  * a stage so boot device implementations should account for this behavior.