diff options
| author | Jean Delvare <khali@linux-fr.org> | 2012-06-29 14:47:19 +0400 |
|---|---|---|
| committer | Mauro Carvalho Chehab <mchehab@redhat.com> | 2012-06-30 02:03:25 +0400 |
| commit | b37d2a3a75cb0e72e18c29336cb2095b63dabfc8 (patch) | |
| tree | 212e01d73f40881626b54ef4811de3a061788989 | |
| parent | a99817ca60d206be3645d156f755cf065e949c58 (diff) | |
| download | linux-b37d2a3a75cb0e72e18c29336cb2095b63dabfc8.tar.xz | |
[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>
| -rw-r--r-- | drivers/i2c/i2c-core.c | 44 | ||||
| -rw-r--r-- | include/linux/i2c.h | 3 |
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, |