libdiskconfig: set MBR signature when creating MBR

When formatting a blank SD card, it needs to set MBR signature when creating MBR.
If not, the 'format' operation will fail.

Change-Id: I860731243797d4da83f370af52822536983009ee
Signed-off-by: Cylen Yao <cylen.yao@mediatek.com>

1 files changed, 27 insertions, 0 deletions

diff --git a/libdiskconfig/config_mbr.c b/libdiskconfig/config_mbr.c
index 7641b29..82d0066 100644
--- a/libdiskconfig/config_mbr.c
+++ b/libdiskconfig/config_mbr.c
@@ -208,6 +208,26 @@ fail:
 }
 
 
+static struct write_list *
+mk_mbr_sig()
+{
+    struct write_list *item;
+    if (!(item = alloc_wl(sizeof(uint16_t)))) {
+        ALOGE("Unable to allocate memory for MBR signature.");
+        return NULL;
+    }
+
+    {
+        /* DO NOT DEREFERENCE */
+        struct pc_boot_record *mbr = (void *)PC_MBR_DISK_OFFSET;
+        /* grab the offset in mbr where to write mbr signature. */
+        item->offset = (loff_t)((uint32_t)((uint8_t *)(&mbr->mbr_sig)));
+    }
+
+    *((uint16_t*)item->data) = PC_BIOS_BOOT_SIG;
+    return item;
+}
+
 struct write_list *
 config_mbr(struct disk_info *dinfo)
 {
@@ -276,6 +296,13 @@ config_mbr(struct disk_info *dinfo)
         wlist_add(&wr_list, temp_wr);
     }
 
+    if ((temp_wr = mk_mbr_sig()))
+        wlist_add(&wr_list, temp_wr);
+    else {
+        ALOGE("Cannot set MBR signature");
+        goto fail;
+    }
+
     return wr_list;
 
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