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From: Russell King <rmk+kernel@armlinux.org.uk>
To: Peter Rosin <peda@axentia.se>
Cc: Wolfram Sang <wsa@the-dreams.de>,
	linux-i2c@vger.kernel.org, linux-arm-kernel@lists.infradead.org
Subject: [PATCH] i2c: mux: pca954x: fix i2c mux selection caching
Date: Fri, 16 Dec 2016 20:06:11 +0000	[thread overview]
Message-ID: <E1cHylf-00071o-KZ@rmk-PC.armlinux.org.uk> (raw)

smbus functions return -ve on error, 0 on success.  However,
__i2c_transfer() have a different return signature - -ve on error, or
number of buffers transferred (which may be zero or greater.)

The upshot of this is that the sense of the test is reversed when using
the mux on a bus supporting the master_xfer method: we cache the value
and never retry if we fail to transfer any buffers, but if we succeed,
we clear the cached value.

Fix this.

Fixes: 463e8f845cbf ("i2c: mux: pca954x: retry updating the mux selection on failure")
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
---
 drivers/i2c/muxes/i2c-mux-pca954x.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/i2c/muxes/i2c-mux-pca954x.c b/drivers/i2c/muxes/i2c-mux-pca954x.c
index 8bc3d36d2837..b6d62ecbd5b6 100644
--- a/drivers/i2c/muxes/i2c-mux-pca954x.c
+++ b/drivers/i2c/muxes/i2c-mux-pca954x.c
@@ -179,7 +179,7 @@ static int pca954x_select_chan(struct i2c_mux_core *muxc, u32 chan)
 	/* Only select the channel if its different from the last channel */
 	if (data->last_chan != regval) {
 		ret = pca954x_reg_write(muxc->parent, client, regval);
-		data->last_chan = ret ? 0 : regval;
+		data->last_chan = ret >= 0 ? regval : 0;
 	}
 
 	return ret;
-- 
2.7.4

WARNING: multiple messages have this Message-ID (diff)
From: rmk+kernel@armlinux.org.uk (Russell King)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH] i2c: mux: pca954x: fix i2c mux selection caching
Date: Fri, 16 Dec 2016 20:06:11 +0000	[thread overview]
Message-ID: <E1cHylf-00071o-KZ@rmk-PC.armlinux.org.uk> (raw)

smbus functions return -ve on error, 0 on success.  However,
__i2c_transfer() have a different return signature - -ve on error, or
number of buffers transferred (which may be zero or greater.)

The upshot of this is that the sense of the test is reversed when using
the mux on a bus supporting the master_xfer method: we cache the value
and never retry if we fail to transfer any buffers, but if we succeed,
we clear the cached value.

Fix this.

Fixes: 463e8f845cbf ("i2c: mux: pca954x: retry updating the mux selection on failure")
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
---
 drivers/i2c/muxes/i2c-mux-pca954x.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/i2c/muxes/i2c-mux-pca954x.c b/drivers/i2c/muxes/i2c-mux-pca954x.c
index 8bc3d36d2837..b6d62ecbd5b6 100644
--- a/drivers/i2c/muxes/i2c-mux-pca954x.c
+++ b/drivers/i2c/muxes/i2c-mux-pca954x.c
@@ -179,7 +179,7 @@ static int pca954x_select_chan(struct i2c_mux_core *muxc, u32 chan)
 	/* Only select the channel if its different from the last channel */
 	if (data->last_chan != regval) {
 		ret = pca954x_reg_write(muxc->parent, client, regval);
-		data->last_chan = ret ? 0 : regval;
+		data->last_chan = ret >= 0 ? regval : 0;
 	}
 
 	return ret;
-- 
2.7.4

             reply	other threads:[~2016-12-16 20:06 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-12-16 20:06 Russell King [this message]
2016-12-16 20:06 ` [PATCH] i2c: mux: pca954x: fix i2c mux selection caching Russell King
2016-12-16 21:20 ` Peter Rosin
2016-12-16 21:20   ` Peter Rosin
2016-12-16 23:23   ` Russell King - ARM Linux
2016-12-16 23:23     ` Russell King - ARM Linux
2016-12-17  6:50     ` Peter Rosin
2016-12-17  6:50       ` Peter Rosin
2016-12-17 12:10 Russell King
2016-12-17 18:30 ` Wolfram Sang

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