fastboot: sparse: implement reserve()

In order to process the CHUNK_TYPE_DONT_CARE properly, there is
a requirement to be able to 'reserve' a specified number of blocks
in the storage media. Because of the special handling of "bad blocks"
in NAND devices, this is implemented in a storage abstraction function.

Signed-off-by: Steve Rae <srae@broadcom.com>
Reviewed-by: Maxime Ripard <maxime.ripard@free-electrons.com>
diff --git a/common/fb_nand.c b/common/fb_nand.c
index 77ca55d..c8c79e9 100644
--- a/common/fb_nand.c
+++ b/common/fb_nand.c
@@ -126,6 +126,25 @@
 	return written / info->blksz;
 }
 
+static lbaint_t fb_nand_sparse_reserve(struct sparse_storage *info,
+		lbaint_t blk, lbaint_t blkcnt)
+{
+	int bad_blocks = 0;
+
+/*
+ * TODO - implement a function to determine the total number
+ * of blocks which must be used in order to reserve the specified
+ * number ("blkcnt") of "good-blocks", starting at "blk"...
+ * ( possibly something like the "check_skip_len()" function )
+ */
+
+	/*
+	 * the return value must be 'blkcnt' ("good-blocks") plus the
+	 * number of "bad-blocks" encountered within this space...
+	 */
+	return blkcnt + bad_blocks;
+}
+
 void fb_nand_flash_write(const char *cmd, void *download_buffer,
 			 unsigned int download_bytes)
 {
@@ -155,6 +174,7 @@
 		sparse.start = part->offset / sparse.blksz;
 		sparse.size = part->size / sparse.blksz;
 		sparse.write = fb_nand_sparse_write;
+		sparse.reserve = fb_nand_sparse_reserve;
 
 		printf("Flashing sparse image at offset " LBAFU "\n",
 		       sparse.start);