W1: ds2490.c ds_write_bit, grouping error, disable readback
David Fries [Thu, 16 Oct 2008 05:05:04 +0000 (22:05 -0700)]
ds_write_bit doesn't read the input buffer, so add COMM_ICP and a comment
that it will no longer generate a read back data byte.  If there is an
extra data byte later on then it will cause an error and discard what data
was there.  Corrected operator ordering for ds_send_control.

Signed-off-by: David Fries <david@fries.net>
Signed-off-by: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/w1/masters/ds2490.c

index 6b188e8..6fabf58 100644 (file)
@@ -525,7 +525,12 @@ static int ds_write_bit(struct ds_device *dev, u8 bit)
        int err;
        struct ds_status st;
 
-       err = ds_send_control(dev, COMM_BIT_IO | COMM_IM | (bit) ? COMM_D : 0, 0);
+       /* Set COMM_ICP to write without a readback.  Note, this will
+        * produce one time slot, a down followed by an up with COMM_D
+        * only determing the timing.
+        */
+       err = ds_send_control(dev, COMM_BIT_IO | COMM_IM | COMM_ICP |
+               (bit ? COMM_D : 0), 0);
        if (err)
                return err;