[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>
diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
index feb7dc3..ccc6445 100644
--- a/drivers/i2c/i2c-core.c
+++ b/drivers/i2c/i2c-core.c
@@ -1295,6 +1295,37 @@
*/
/**
+ * __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 @@
*/
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 @@
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;