W1: ds2490.c ds_write_bit, grouping error, disable readback

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>

1 files changed, 6 insertions, 1 deletions

diff --git a/drivers/w1/masters/ds2490.c b/drivers/w1/masters/ds2490.c
index 6b188e8008e4..6fabf584395f 100644
--- a/drivers/w1/masters/ds2490.c
+++ b/drivers/w1/masters/ds2490.c
@@ -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;