[PATCH] i2c-cpm: Detect and report NAK right away instead of timing out.

Mike Ditto mditto at consentry.com
Sat Nov 1 11:29:25 EST 2008

Make the driver report an ENXIO error immediately upon NAK instead of
waiting for another interrupt and getting a timeout.

Signed-off-by: Mike Ditto <mditto at consentry.com>
When reading from a device that is not present or declines to respond
to, e.g., a non-existent register address, CPM immediately reports a
NAK condition in the TxBD, but the driver kept waiting until a timeout,
which takes 1 second and causes an ugly console error message.

Index: linux/drivers/i2c/busses/i2c-cpm.c
retrieving revision 1.3
diff -u -p -r1.3 i2c-cpm.c
--- linux/drivers/i2c/busses/i2c-cpm.c	31 Oct 2008 06:36:08 -0000	1.3
+++ linux/drivers/i2c/busses/i2c-cpm.c	1 Nov 2008 00:12:45 -0000
@@ -369,6 +369,7 @@ static int cpm_i2c_xfer(struct i2c_adapt
 		pmsg = &msgs[tptr];
 		if (pmsg->flags & I2C_M_RD)
 			ret = wait_event_interruptible_timeout(cpm->i2c_wait,
+				(in_be16(&tbdf[tptr].cbd_sc) & BD_SC_NAK) ||
 				!(in_be16(&rbdf[rptr].cbd_sc) & BD_SC_EMPTY),
 				1 * HZ);

More information about the Linuxppc-dev mailing list