accel: Fix getting scale for sensors with IIO_SHARED_BY_ALL mask

Properties with the IIO_SHARED_BY_ALL mask don't have the sensor type prefix
before the filename, causing some devices to not have a scale set from sysfs.

Fix this by searching through sysfs for both properties name: scale and
in_accel_scale.

Tested on: Cyan (Acer Chromebook R11, with 2 accelerometers)
Affects: All chromebooks with cros-ec sensors
https://github.com/torvalds/linux/tree/master/drivers/iio/common/cros_ec_sensors

src/Makefile.am

@@ -28,8 +28,8 @@ iio_sensor_proxy_SOURCES =			\
 	iio-buffer-utils.c			\
 	accel-mount-matrix.h			\
 	accel-mount-matrix.c			\
-	accel-location.h				\
-	accel-location.c				\
+	accel-attributes.h				\
+	accel-attributes.c				\
 	$(BUILT_SOURCES)
 
 iio_sensor_proxy_CPPFLAGS =			\
@@ -63,8 +63,8 @@ test_mount_matrix_LDADD = $(IIO_SENSOR_PROXY_LIBS)
 
 test_accel_location_SOURCES =			\
 	test-accel-location.c			\
-	accel-location.h			\
-	accel-location.c
+	accel-attributes.h			\
+	accel-attributes.c
 
 test_accel_location_CPPFLAGS =			\
 	$(IIO_SENSOR_PROXY_CFLAGS)		\

src/accel-attributes.c

@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2019 Luís Ferreira <luis@aurorafoss.org>
+ * Copyright (c) 2019 Daniel Stuart <daniel.stuart@pucpr.edu.br>
  *
  * This program is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 3 as published by
@@ -7,7 +8,7 @@
  *
  */
 
-#include "accel-location.h"
+#include "accel-attributes.h"
 
 AccelLocation
 setup_accel_location (GUdevDevice *device)
@@ -55,3 +56,23 @@ parse_accel_location (const char *location, AccelLocation *value)
 		return FALSE;
 	}
 }
+
+gdouble
+get_accel_scale (GUdevDevice *device)
+{
+	gdouble scale;
+
+	scale = g_udev_device_get_sysfs_attr_as_double (device, "in_accel_scale");
+	if (scale != 0.0) {
+		g_debug ("Attribute in_accel_scale ('%f') found on sysfs", scale);
+		return scale;
+	}
+	scale = g_udev_device_get_sysfs_attr_as_double (device, "scale");
+	if (scale != 0.0) {
+		g_debug ("Attribute scale ('%f') found on sysfs", scale);
+		return scale;
+	}
+
+	g_debug ("Failed to auto-detect scale, falling back to 1.0");
+	return 1.0;
+}

src/accel-attributes.h

@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2019 Luís Ferreira <luis@aurorafoss.org>
+ * Copyright (c) 2019 Daniel Stuart <daniel.stuart@pucpr.edu.br>
  *
  * This program is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 3 as published by
@@ -19,3 +20,5 @@ AccelLocation setup_accel_location (GUdevDevice *device);
 
 gboolean parse_accel_location (const char    *location,
                                AccelLocation *value);
+
+gdouble get_accel_scale (GUdevDevice *device);

src/drivers.h

@@ -9,7 +9,7 @@
 #include <glib.h>
 #include <gudev/gudev.h>
 
-#include "accel-location.h"
+#include "accel-attributes.h"
 
 typedef enum {
 	DRIVER_TYPE_ACCEL,

src/drv-iio-poll-accel.c

@@ -25,8 +25,7 @@ typedef struct DrvData {
 	const char         *name;
 	AccelVec3          *mount_matrix;
 	AccelLocation       location;
-
-	double              scale;
+	gdouble             scale;
 } DrvData;
 
 static DrvData *drv_data = NULL;
@@ -128,9 +127,7 @@ iio_poll_accel_open (GUdevDevice        *device,
 	drv_data->location = setup_accel_location (device);
 	drv_data->callback_func = callback_func;
 	drv_data->user_data = user_data;
-	drv_data->scale = g_udev_device_get_sysfs_attr_as_double (device, "in_accel_scale");
-	if (drv_data->scale == 0.0)
-		drv_data->scale = 1.0;
+	drv_data->scale = get_accel_scale (device);
 
 	return TRUE;
 }

src/test-accel-location.c

@@ -7,7 +7,7 @@
  *
  */
 
-#include "accel-location.h"
+#include "accel-attributes.h"
 
 #define VALID_DISPLAY_LOCATION "display"
 #define VALID_BASE_LOCATION "base"