iio: Improve iio channel parsing to add enabled channels

scale and other attributes have to be read individually as they vary quite alot
depending on the channel. We only care/take data from scan_elements

Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com>

api/mraa/iio.h

@@ -38,7 +38,6 @@ typedef struct {
     unsigned int bytes;
     unsigned int shift;
     unsigned int location;
-    float scale;
 } mraa_iio_channel;
 
 /**

examples/iio_driver.c

@@ -29,15 +29,13 @@ static void
 printword(uint16_t input, mraa_iio_channel *chan)
 {
     int16_t res;
+
     if (!chan->lendian) {
             input = be16toh(input);
     } else {
             input = le16toh(input);
     }
 
-    // currently we don't treat scales
-    chan->scale = 1.0f;
-
     input >>= chan->shift;
     input &= chan->mask;
     if (chan->signedd) {
@@ -45,7 +43,7 @@ printword(uint16_t input, mraa_iio_channel *chan)
     } else {
         res = input;
     }
-    printf("chan %d == %05f\n", chan->index, ((float)res + chan->offset) * chan->scale);
+    printf("  value = %05f\n", chan->index, (float)res);
 }
 
 mraa_iio_context iio_device0;
@@ -57,13 +55,14 @@ interrupt(char* data)
     int i = 0;
 
     for (i; i < mraa_iio_get_channel_count(iio_device0); i++) {
-        printf("channel bytes %d\n", channels[i].bytes);
+        if (channels[i].enabled) {
+            printf("channel %d - bytes %d\n", channels[i].index, channels[i].bytes);
             switch (channels[i].bytes) {
                 case 2:
                     printword(*(uint16_t *)(data + channels[i].location), &channels[i]);
             }
         }
-    printf("data %s\n", (char*) data);
+    }
 }
 
 int

src/iio/iio.c

@@ -105,6 +105,7 @@ mraa_iio_get_channel_data(mraa_iio_context dev)
 
                 buf[(strlen(buf)-5)] = '\0';
                 char* str = strdup(buf);
+                // grab the type of the buffer
                 snprintf(buf, MAX_SIZE, "%stype", str);
                 fd = open(buf, O_RDONLY);
                 if (fd > 0) {
@@ -119,8 +120,11 @@ mraa_iio_get_channel_data(mraa_iio_context dev)
                         chan->location = curr_bytes - curr_bytes%chan->bytes + chan->bytes;
                     }
                     curr_bytes = chan->location + chan->bytes;
-                    if (ret < 0) {
                     // probably should be 5?
+                    if (ret < 0) {
+                        // cleanup
+                        free(str);
+                        close(fd);
                         return MRAA_IO_SETUP_FAILURE;
                     }
                     chan->signedd = (signchar == 's');
@@ -130,10 +134,21 @@ mraa_iio_get_channel_data(mraa_iio_context dev)
                     } else {
                         chan->mask = (1 << chan->bits_used) - 1;
                     }
-
                     close(fd);
                 }
-                // todo - read scale & _en attributes
+                // grab the enable flag of channel
+                snprintf(buf, MAX_SIZE, "%sen", str);
+                fd = open(buf, O_RDONLY);
+                if (fd > 0) {
+                    if (read(fd, readbuf, 2 * sizeof(char)) != 2) {
+                        syslog(LOG_ERR, "iio: Failed to read a sensible value from sysfs");
+                        return -1;
+                    }
+                    chan->enabled = (int) strtol(readbuf, NULL, 10);
+                    close(fd);
+                }
+                // clean up str var
+                free(str);
             }
         }
     }

src/mraa.c

@@ -173,13 +173,14 @@ mraa_init()
         device->num = i;
         snprintf(filepath, 64, "/sys/bus/iio/devices/iio:device%d/name", i);
         fd = open(filepath, O_RDONLY);
-        if (fd != -1) {
+        if (fd > 0) {
             len = read(fd, &name, 64);
             if (len > 1) {
                 // use strndup
                 device->name = malloc((sizeof(char) * len) + sizeof(char));
                 strncpy(device->name, name, len);
             }
+            close(fd);
         }
     }