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authorJean Delvare <khali@linux-fr.org>2012-06-29 07:47:19 -0300
committerMauro Carvalho Chehab <mchehab@redhat.com>2012-06-29 19:03:25 -0300
commitb37d2a3a75cb0e72e18c29336cb2095b63dabfc8 (patch)
tree212e01d73f40881626b54ef4811de3a061788989 /drivers/i2c/i2c-core.c
parenta99817ca60d206be3645d156f755cf065e949c58 (diff)
downloadlinux-b37d2a3a75cb0e72e18c29336cb2095b63dabfc8.tar.gz
[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>
Diffstat (limited to 'drivers/i2c/i2c-core.c')
-rw-r--r--drivers/i2c/i2c-core.c44
1 files changed, 33 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;