linux-kernel - [PATCH 21/30] W1: ds2490.c ds_write_bit, grouping error, disable readback

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Message-Id: <12157843061992-git-send-email-johnpol@2ka.mipt.ru>
Date:	Fri, 11 Jul 2008 17:51:36 +0400
From:	Evgeniy Polyakov <johnpol@....mipt.ru>
To:	linux-kernel@...r.kernel.org
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	David Fries <david@...es.net>,
	Evgeniy Polyakov <johnpol@....mipt.ru>
Subject: [PATCH 21/30] 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@...es.net>
Signed-off-by: Evgeniy Polyakov <johnpol@....mipt.ru>

---
 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 8ab2c86..7acf6d2 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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