@@ -82,6 +82,7 @@
*/
#define AK8975_MAX_CONVERSION_TIMEOUT 500
#define AK8975_CONVERSION_DONE_POLL_TIME 10
+#define RAW_TO_GAUSS(asa) ((((asa) + 128) * 3000) / 256)
/*
* Per-instance context data for the device.
@@ -223,15 +224,15 @@ static int ak8975_setup(struct i2c_client *client)
*
* Since 1uT = 100 gauss, our final scale factor becomes:
*
- * Hadj = H * ((ASA + 128) / 256) * 3/10 * 100
- * Hadj = H * ((ASA + 128) * 30 / 256
+ * Hadj = H * ((ASA + 128) / 256) * 3/10 * 1/100
+ * Hadj = H * ((ASA + 128) * 0.003) / 256
*
* Since ASA doesn't change, we cache the resultant scale factor into the
* device context in ak8975_setup().
*/
- data->raw_to_gauss[0] = ((data->asa[0] + 128) * 30) >> 8;
- data->raw_to_gauss[1] = ((data->asa[1] + 128) * 30) >> 8;
- data->raw_to_gauss[2] = ((data->asa[2] + 128) * 30) >> 8;
+ data->raw_to_gauss[0] = RAW_TO_GAUSS(data->asa[0]);
+ data->raw_to_gauss[1] = RAW_TO_GAUSS(data->asa[1]);
+ data->raw_to_gauss[2] = RAW_TO_GAUSS(data->asa[2]);
return 0;
}
@@ -434,8 +435,9 @@ static int ak8975_read_raw(struct iio_dev *indio_dev,
case IIO_CHAN_INFO_RAW:
return ak8975_read_axis(indio_dev, chan->address, val);
case IIO_CHAN_INFO_SCALE:
- *val = data->raw_to_gauss[chan->address];
- return IIO_VAL_INT;
+ *val = 0;
+ *val2 = data->raw_to_gauss[chan->address];
+ return IIO_VAL_INT_PLUS_MICRO;
}
return -EINVAL;
}
This is a note to let you know that I have just added a patch titled iio: ak8975: Fix calculation formula for convert micro tesla to gauss to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree which can be found at: http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 3.5.y.z tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Luis ------ From 891600f4ac6fa37a2e63daba5e1cf291754dbb0e Mon Sep 17 00:00:00 2001 From: Beomho Seo <beomho.seo@samsung.com> Date: Wed, 2 Apr 2014 09:15:00 +0100 Subject: iio: ak8975: Fix calculation formula for convert micro tesla to gauss unit commit bef44abccb2677e8d16e50b75316d4fd1061be81 upstream. This effects the reported scale of the raw values, and thus userspace applications that use this value. One micro tesla equal 0.01 gauss. So I have fixed calculation formula And add RAW_TO_GAUSS macro. ASA is in the range of 0 to 255. If multiply 0.003, calculation result(in_magn_[*]_scale) is always 0. So multiply 3000 and return and IIO_VAL_INT_PLUS_MICRO. As a result, read_raw call back function return accurate scale value. Signed-off-by: Beomho Seo <beomho.seo@samsung.com> Signed-off-by: Jonathan Cameron <jic23@kernel.org> [ luis: backported to 3.5: ak8975 driver is in staging, adjusted file name ] Signed-off-by: Luis Henriques <luis.henriques@canonical.com> --- drivers/staging/iio/magnetometer/ak8975.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-) -- 1.9.0