linux-kernel - [PATCH 10/11] staging: iio: adt7316: change interpretation of write to dac update mode

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Date:   Tue, 11 Dec 2018 17:55:02 -0700
From:   Jeremy Fertic <jeremyfertic@...il.com>
To:     Jonathan Cameron <jic23@...nel.org>
Cc:     Lars-Peter Clausen <lars@...afoo.de>,
        Michael Hennerich <Michael.Hennerich@...log.com>,
        Hartmut Knaack <knaack.h@....de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-iio@...r.kernel.org, devel@...verdev.osuosl.org,
        linux-kernel@...r.kernel.org,
        Jeremy Fertic <jeremyfertic@...il.com>
Subject: [PATCH 10/11] staging: iio: adt7316: change interpretation of write to dac update mode

Based on the output of adt7316_show_all_DAC_update_modes() and
adt7316_show_DAC_update_mode(), adt7316_store_DAC_update_mode() should
expect the user to enter an integer input from 0 to 3. The user input is
currently expected to account for the actual bit positions in the register.
For example, choosing option 3 would require a write of 0x30 (actually 48
since it expects base 10). To address this inconsistency, create a shift
macro to be used in the valid input check as well as the calculation for
the register write.

Signed-off-by: Jeremy Fertic <jeremyfertic@...il.com>
---
I'm not sure if this patch is appropriate since it's making a user visible
change. I've included it since the driver is still in staging.

 drivers/staging/iio/addac/adt7316.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/iio/addac/adt7316.c b/drivers/staging/iio/addac/adt7316.c
index bca599d8c51c..58b462ad0c83 100644
--- a/drivers/staging/iio/addac/adt7316.c
+++ b/drivers/staging/iio/addac/adt7316.c
@@ -129,6 +129,7 @@
  */
 #define ADT7316_DA_2VREF_CH_MASK	0xF
 #define ADT7316_DA_EN_MODE_MASK		0x30
+#define ADT7316_DA_EN_MODE_SHIFT	4
 #define ADT7316_DA_EN_MODE_SINGLE	0x00
 #define ADT7316_DA_EN_MODE_AB_CD	0x10
 #define ADT7316_DA_EN_MODE_ABCD		0x20
@@ -879,11 +880,11 @@ static ssize_t adt7316_store_DAC_update_mode(struct device *dev,
 		return -EPERM;
 
 	ret = kstrtou8(buf, 10, &data);
-	if (ret || data > ADT7316_DA_EN_MODE_MASK)
+	if (ret || data > (ADT7316_DA_EN_MODE_MASK >> ADT7316_DA_EN_MODE_SHIFT))
 		return -EINVAL;
 
 	dac_config = chip->dac_config & (~ADT7316_DA_EN_MODE_MASK);
-	dac_config |= data;
+	dac_config |= data << ADT7316_DA_EN_MODE_SHIFT;
 
 	ret = chip->bus.write(chip->bus.client, ADT7316_DAC_CONFIG, dac_config);
 	if (ret)
-- 
2.19.1