[media] i2c: Export an unlocked flavor of i2c_transfer

Some drivers (in particular for TV cards) need exclusive access to
their I2C buses for specific operations. Export an unlocked flavor
of i2c_transfer to give them full control.

The unlocked flavor has the following limitations:
* Obviously, caller must hold the i2c adapter lock.
* No debug messages are logged. We don't want to log messages while
  holding a rt_mutex.
* No check is done on the existence of adap->algo->master_xfer. It
  is thus the caller's responsibility to ensure that the function is
  OK to call.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

2 files changed, 36 insertions, 11 deletions

diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
index feb7dc359186..ccc6445979c4 100644
--- a/drivers/i2c/i2c-core.c
+++ b/drivers/i2c/i2c-core.c
@@ -1295,6 +1295,37 @@ module_exit(i2c_exit);
  */
 
 /**
+ * __i2c_transfer - unlocked flavor of i2c_transfer
+ * @adap: Handle to I2C bus
+ * @msgs: One or more messages to execute before STOP is issued to
+ *      terminate the operation; each message begins with a START.
+ * @num: Number of messages to be executed.
+ *
+ * Returns negative errno, else the number of messages executed.
+ *
+ * Adapter lock must be held when calling this function. No debug logging
+ * takes place. adap->algo->master_xfer existence isn't checked.
+ */
+int __i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
+{
+        unsigned long orig_jiffies;
+        int ret, try;
+
+        /* Retry automatically on arbitration loss */
+        orig_jiffies = jiffies;
+        for (ret = 0, try = 0; try <= adap->retries; try++) {
+                ret = adap->algo->master_xfer(adap, msgs, num);
+                if (ret != -EAGAIN)
+                        break;
+                if (time_after(jiffies, orig_jiffies + adap->timeout))
+                        break;
+        }
+
+        return ret;
+}
+EXPORT_SYMBOL(__i2c_transfer);
+
+/**
  * i2c_transfer - execute a single or combined I2C message
  * @adap: Handle to I2C bus
  * @msgs: One or more messages to execute before STOP is issued to
@@ -1308,8 +1339,7 @@ module_exit(i2c_exit);
  */
 int i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
 {
-        unsigned long orig_jiffies;
-        int ret, try;
+        int ret;
 
         /* REVISIT the fault reporting model here is weak:
          *
@@ -1347,15 +1377,7 @@ int i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
                         i2c_lock_adapter(adap);
                 }
 
-                /* Retry automatically on arbitration loss */
-                orig_jiffies = jiffies;
-                for (ret = 0, try = 0; try <= adap->retries; try++) {
-                        ret = adap->algo->master_xfer(adap, msgs, num);
-                        if (ret != -EAGAIN)
-                                break;
-                        if (time_after(jiffies, orig_jiffies + adap->timeout))
-                                break;
-                }
+                ret = __i2c_transfer(adap, msgs, num);
                 i2c_unlock_adapter(adap);
 
                 return ret;
diff --git a/include/linux/i2c.h b/include/linux/i2c.h
index 195d8b3d9cfb..a121c012309a 100644
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -68,6 +68,9 @@ extern int i2c_master_recv(const struct i2c_client *client, char *buf,
  */
 extern int i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
                         int num);
+/* Unlocked flavor */
+extern int __i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
+                          int num);
 
 /* This is the very generalized SMBus access routine. You probably do not
    want to use this, though; one of the functions below may be much easier,