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buffer-utils: Fix orientation axis switch using 4.8 kernel

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Using 4.8-rc kernel, orientation got flipped. The right-up became normal
and normal became right-up. The reason for this is that orientation code
of iio-sensor-proxy observes x and y swapped (actually they are not in
the data provided by IIO).

Although it is triggered by some kernel change, the reliance on
g_dir_read_name() to get the correct order of channels is not correct.
We should look at the in_xxx_x_index field and calculate correct byte
offset in the iio buffer data.

For example with 4.8 kernel: from log with added index location printed

** (process:4945): DEBUG: Built channel array for in_accel_y: index: 1, is signed: 1, bytes: 4, bits_used: 32, shift: 0, mask: 0x0, be: 0
** (process:4945): DEBUG: Built channel array for in_accel_x: index: 0, is signed: 1, bytes: 4, bits_used: 32, shift: 0, mask: 0x0, be: 0
** (process:4945): DEBUG: Built channel array for in_accel_z: index: 2, is signed: 1, bytes: 4, bits_used: 32, shift: 0, mask: 0x0, be: 0

(Here in_accel_y appeared before in_accel_x in g_dir_read_name(), because
of that channel array ordering is wrong hence location was
calculated wrong as below)
...
...
** (process:4945): DEBUG: process_scan_1: channel_index: 1, chan_name: in_accel_x, channel_data_index: 0 location: 4
** (process:4945): DEBUG: process_scan_1: channel_index: 0, chan_name: in_accel_y, channel_data_index: 1 location: 0
** (process:4945): DEBUG: process_scan_1: channel_index: 2, chan_name: in_accel_z, channel_data_index: 2 location: 8
** (process:4945): DEBUG: Read from IIO: -880449, 32851, -457812

To fix this we need to calculate the byte offset location using
channel_index not in the order they are returned by g_dir_read_name().

The easiest fix is to sort the array of channels in
build_channel_array() based on index. Also added some debug to print
index and location.

After the fix, the above log will change to:
** (process:4674): DEBUG: Built channel array for in_accel_x: index: 0, is signed: 1, bytes: 4, bits_used: 32, shift: 0, mask: 0x0, be: 0
** (process:4674): DEBUG: Built channel array for in_accel_y: index: 1, is signed: 1, bytes: 4, bits_used: 32, shift: 0, mask: 0x0, be: 0
** (process:4674): DEBUG: Built channel array for in_accel_z: index: 2, is signed: 1, bytes: 4, bits_used: 32, shift: 0, mask: 0x0, be: 0

(Sorted above, so location of byte offset is correct)

** (process:4674): DEBUG: process_scan_1: channel_index: 0, chan_name: in_accel_x, channel_data_index: 0 location: 0
** (process:4674): DEBUG: process_scan_1: channel_index: 1, chan_name: in_accel_y, channel_data_index: 1 location: 4
** (process:4674): DEBUG: process_scan_1: channel_index: 2, chan_name: in_accel_z, channel_data_index: 2 location: 8
** (process:4674): DEBUG: Read from IIO: 34804, -878496, -448046

Closes: #99
This commit is contained in:
Srinivas Pandruvada
2016-09-02 15:11:45 -07:00
committed by Bastien Nocera
parent 0c36d3e617
commit 984803bc1b
1 changed files with 16 additions and 2 deletions
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18
src/iio-buffer-utils.c
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@@ -193,6 +193,15 @@ channel_info_free (iio_channel_info *ci)
g_free (ci);
}
static int
compare_channel_index (gconstpointer a, gconstpointer b)
{
const iio_channel_info *info_1 = a;
const iio_channel_info *info_2 = b;
return (int) (info_1->index - info_2->index);
}
/* build_channel_array() - function to figure out what channels are present */
static iio_channel_info **
build_channel_array (const char *device_dir,
@@ -298,14 +307,16 @@ build_channel_array (const char *device_dir,
g_dir_close (dp);
g_free (scan_el_dir);
g_ptr_array_sort (array, compare_channel_index);
*counter = array->len;
ret_array = (iio_channel_info **) g_ptr_array_free (array, FALSE);
for (i = 0; i < *counter; i++) {
iio_channel_info *ci = ret_array[i];
g_debug ("Built channel array for %s: is signed: %d, bytes: %d, bits_used: %d, shift: %d, mask: 0x%" G_GUINT64_FORMAT ", be: %d",
ci->name, ci->is_signed, ci->bytes, ci->bits_used, ci->shift, ci->mask, ci->be);
g_debug ("Built channel array for %s: index: %d, is signed: %d, bytes: %d, bits_used: %d, shift: %d, mask: 0x%" G_GUINT64_FORMAT ", be: %d",
ci->name, ci->index, ci->is_signed, ci->bytes, ci->bits_used, ci->shift, ci->mask, ci->be);
}
return ret_array;
@@ -474,6 +485,9 @@ process_scan_1 (char *data,
if (strcmp (buffer_data->channels[k]->name, ch_name) != 0)
continue;
g_debug ("process_scan_1: channel_index: %d, chan_name: %s, channel_data_index: %d location: %d",
k, buffer_data->channels[k]->name, buffer_data->channels[k]->index, buffer_data->channels[k]->location);
switch (buffer_data->channels[k]->bytes) {
/* only a few cases implemented so far */
case 4: