Commit b37d2a3a authored by Jean Delvare's avatar Jean Delvare Committed by Mauro Carvalho Chehab
Browse files

[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: default avatarJean Delvare <khali@linux-fr.org>
Signed-off-by: default avatarMauro Carvalho Chehab <mchehab@redhat.com>
parent a99817ca

drivers/i2c/i2c-core.c

+33 −11
Original line number Diff line number Diff line
@@ -1294,6 +1294,37 @@ 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
@@ -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;

include/linux/i2c.h

+3 −0
Original line number Diff line number Diff line
@@ -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,

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