mmc: add basic SDIO I/O operations

Add command wrappers that simplify register access from SDIO
function drivers.

Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>
diff --git a/include/linux/mmc/sdio_func.h b/include/linux/mmc/sdio_func.h
index 13a1a9c..5c56df1 100644
--- a/include/linux/mmc/sdio_func.h
+++ b/include/linux/mmc/sdio_func.h
@@ -49,5 +49,17 @@
 extern int sdio_register_driver(struct sdio_driver *);
 extern void sdio_unregister_driver(struct sdio_driver *);
 
+/*
+ * SDIO I/O operations
+ */
+extern void sdio_claim_host(struct sdio_func *func);
+extern void sdio_release_host(struct sdio_func *func);
+
+extern unsigned char sdio_readb(struct sdio_func *func,
+	unsigned int addr, int *err_ret);
+
+extern void sdio_writeb(struct sdio_func *func, unsigned char b,
+	unsigned int addr, int *err_ret);
+
 #endif