block: reimplement caching

The current caching layer only has a single buffer for
writing and reading. The FAT driver often accesses the
fat and then data again, which currently can't be cached.
Reimplement this with a list of cached chunks. The number
of chunks and their sizes are currently hardcoded, but
that could be easily made configurable.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

1 files changed, 9 insertions, 7 deletions

diff --git a/include/block.h b/include/block.h
index aaab4e3b36..cfa4cb9ef1 100644
--- a/include/block.h
+++ b/include/block.h
@@ -8,21 +8,23 @@ struct block_device;
 struct block_device_ops {
 	int (*read)(struct block_device *, void *buf, int block, int num_blocks);
 	int (*write)(struct block_device *, const void *buf, int block, int num_blocks);
+	int (*read_start)(struct block_device *, void *buf, int block, int num_blocks);
+	int (*read_done)(struct block_device *);
 };
 
+struct chunk;
+
 struct block_device {
 	struct device_d *dev;
 	struct block_device_ops *ops;
 	int blockbits;
 	int num_blocks;
-	void *rdbuf; /* read buffer */
 	int rdbufsize;
-	int rdblock; /* start block in read buffer */
-	int rdblockend; /* end block in read buffer */
-	void *wrbuf; /* write buffer */
-	int wrblock; /* start block in write buffer */
-	int wrbufblocks; /* number of blocks currently in write buffer */
-	int wrbufsize; /* size of write buffer in blocks */
+	int blkmask;
+
+	struct list_head buffered_blocks;
+	struct list_head idle_blocks;
+
 	struct cdev cdev;
 };