From b37d2a3a75cb0e72e18c29336cb2095b63dabfc8 Mon Sep 17 00:00:00 2001 From: Jean Delvare Date: Fri, 29 Jun 2012 07:47:19 -0300 Subject: [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 Signed-off-by: Mauro Carvalho Chehab --- drivers/i2c/i2c-core.c | 44 +++++++++++++++++++++++++++++++++----------- 1 file changed, 33 insertions(+), 11 deletions(-) (limited to 'drivers/i2c') 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 @@ 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; -- cgit v1.1