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[media] i2c: Export an unlocked flavor of i2c_transfer

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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>
This commit is contained in:
Jean Delvare 2012-06-29 07:47:19 -03:00 • committed by Mauro Carvalho Chehab
parent a99817ca60
commit b37d2a3a75
2 changed files with 36 additions and 11 deletions
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3
include/linux/i2c.h
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@ -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,