linux-kernel - [PATCH 26/35] W1: ds2490.c ds_write

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Message-ID: <20080328122720.GA3613@spacedout.fries.net>
Date:	Fri, 28 Mar 2008 07:27:20 -0500
From:	David Fries <david@...es.net>
To:	linux-kernel@...r.kernel.org
Cc:	Evgeniy Polyakov <johnpol@....mipt.ru>
Subject: [PATCH 26/35] W1: ds2490.c ds_write_bit disable readback

ds2490.c 1.11
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.

Signed-off-by: David Fries <david@...es.net>
---
 drivers/w1/masters/ds2490.c |    7 ++++++-
 1 files changed, 6 insertions(+), 1 deletions(-)

diff --git a/drivers/w1/masters/ds2490.c b/drivers/w1/masters/ds2490.c
index 6778bd3..e0e9325 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;
 
-- 
1.4.4.4

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