sdio: add sdio_f0_readb() and sdio_f0_writeb()

Add sdio_f0_readb() and sdio_f0_writeb() functions to reading and
writing function 0 registers.  Writes outside the vendor specific CCCR
registers (0xF0 - 0xFF) are not permitted.

Signed-off-by: David Vrabel <david.vrabel@csr.com>
Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>

2 files changed, 69 insertions, 0 deletions

diff --git a/drivers/mmc/core/sdio_io.c b/drivers/mmc/core/sdio_io.c
index 34b085d4024a..625b92ce9cef 100644
--- a/drivers/mmc/core/sdio_io.c
+++ b/drivers/mmc/core/sdio_io.c
@@ -482,3 +482,67 @@ void sdio_writel(struct sdio_func *func, unsigned long b, unsigned int addr,
 }
 EXPORT_SYMBOL_GPL(sdio_writel);
 
+/**
+ *      sdio_f0_readb - read a single byte from SDIO function 0
+ *      @func: an SDIO function of the card
+ *      @addr: address to read
+ *      @err_ret: optional status value from transfer
+ *
+ *      Reads a single byte from the address space of SDIO function 0.
+ *      If there is a problem reading the address, 0xff is returned
+ *      and @err_ret will contain the error code.
+ */
+unsigned char sdio_f0_readb(struct sdio_func *func, unsigned int addr,
+        int *err_ret)
+{
+        int ret;
+        unsigned char val;
+
+        BUG_ON(!func);
+
+        if (err_ret)
+                *err_ret = 0;
+
+        ret = mmc_io_rw_direct(func->card, 0, 0, addr, 0, &val);
+        if (ret) {
+                if (err_ret)
+                        *err_ret = ret;
+                return 0xFF;
+        }
+
+        return val;
+}
+EXPORT_SYMBOL_GPL(sdio_f0_readb);
+
+/**
+ *      sdio_f0_writeb - write a single byte to SDIO function 0
+ *      @func: an SDIO function of the card
+ *      @b: byte to write
+ *      @addr: address to write to
+ *      @err_ret: optional status value from transfer
+ *
+ *      Writes a single byte to the address space of SDIO function 0.
+ *      @err_ret will contain the status of the actual transfer.
+ *
+ *      Only writes to the vendor specific CCCR registers (0xF0 -
+ *      0xFF) are permiited; @err_ret will be set to -EINVAL for *
+ *      writes outside this range.
+ */
+void sdio_f0_writeb(struct sdio_func *func, unsigned char b, unsigned int addr,
+        int *err_ret)
+{
+        int ret;
+
+        BUG_ON(!func);
+
+        if (addr < 0xF0 || addr > 0xFF) {
+                if (err_ret)
+                        *err_ret = -EINVAL;
+                return;
+        }
+
+        ret = mmc_io_rw_direct(func->card, 1, 0, addr, b, NULL);
+        if (err_ret)
+                *err_ret = ret;
+}
+EXPORT_SYMBOL_GPL(sdio_f0_writeb);
diff --git a/include/linux/mmc/sdio_func.h b/include/linux/mmc/sdio_func.h
index f05757984e8d..da6a96c39776 100644
--- a/include/linux/mmc/sdio_func.h
+++ b/include/linux/mmc/sdio_func.h
@@ -141,5 +141,10 @@ extern int sdio_memcpy_toio(struct sdio_func *func, unsigned int addr,
 extern int sdio_writesb(struct sdio_func *func, unsigned int addr,
         void *src, int count);
 
+extern unsigned char sdio_f0_readb(struct sdio_func *func,
+        unsigned int addr, int *err_ret);
+extern void sdio_f0_writeb(struct sdio_func *func, unsigned char b,
+        unsigned int addr, int *err_ret);
+
 #endif