V4L/DVB (6633): xc2028: make register reads atomic

Issuing register reads as a separate address write and data read transactions
means that other I2C activity could occur in between and state could get out
of sync.  Issue both the write and read in a single transaction so that the
i2c layer can prevent other users accessing the bus until we are complete.

Signed-off-by: Chris Pascoe <c.pascoe@itee.uq.edu.au>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>

1 files changed, 13 insertions, 0 deletions

diff --git a/drivers/media/video/tuner-i2c.h b/drivers/media/video/tuner-i2c.h
index b5ac189ba40f..d7cf72c3fd71 100644
--- a/drivers/media/video/tuner-i2c.h
+++ b/drivers/media/video/tuner-i2c.h
@@ -46,6 +46,19 @@ static inline int tuner_i2c_xfer_recv(struct tuner_i2c_props *props, char *buf,
         return (ret == 1) ? len : ret;
 }
 
+static inline int tuner_i2c_xfer_send_recv(struct tuner_i2c_props *props,
+                                           char *obuf, int olen,
+                                           char *ibuf, int ilen)
+{
+        struct i2c_msg msg[2] = { { .addr = props->addr, .flags = 0,
+                                    .buf = obuf, .len = olen },
+                                  { .addr = props->addr, .flags = I2C_M_RD,
+                                    .buf = ibuf, .len = ilen } };
+        int ret = i2c_transfer(props->adap, msg, 2);
+
+        return (ret == 2) ? ilen : ret;
+}
+
 #ifndef __TUNER_DRIVER_H__
 #define tuner_warn(fmt, arg...) do {                                    \
         printk(KERN_WARNING "%s %d-%04x: " fmt, PREFIX,                 \