mraa.c: Find i2c bus by pci id

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

include/mraa_internal.h

@@ -149,6 +149,16 @@ int mraa_find_i2c_bus(const char* devname, int startfrom);
  */
 mraa_result_t mraa_atoi(char* intStr, int* value);
 
+/**
+ * helper function to find an i2c bus based on pci data
+ *
+ * @param pci_device
+ * @param pci_id on pci_device
+ * @param i2c adapter name & number
+ * @return the matching i2c-dev bus id or -1
+ */
+int mraa_find_i2c_bus_pci(const char* pci_device, const char *pci_id, const char* adapter_name);
+
 #if defined(IMRAA)
 /**
  * read Imraa subplatform lock file, caller is responsible to free return

src/mraa.c

@@ -928,6 +928,49 @@ mraa_count_i2c_files(const char* path, const struct stat* sb, int flag, struct F
     return 0;
 }
 
+int
+mraa_find_i2c_bus_pci(const char* pci_device, const char *pci_id, const char* adapter_name)
+{
+    /**
+     * For example we'd get something like:
+     * pci0000:00/0000:00:16.3/i2c_desiignware.3
+     */
+    char path[1024];
+    snprintf(path, 1024-1, "/sys/devices/pci%s/%s/%s/", pci_device, pci_id, adapter_name);
+    if (mraa_file_exist(path)) {
+        struct dirent **namelist;
+        int n;
+        n = scandir(path, &namelist, NULL, alphasort);
+        if (n < 0) {
+            syslog(LOG_ERR, "Failed to get information on i2c");
+            return -1;
+        }
+        else {
+            while (n--) {
+	        char* dup = strdup(namelist[n]->d_name);
+                const char delim = '-';
+                char* token;
+                token = strsep(&dup, &delim);
+                if (token != NULL) {
+                    if (strncmp("i2c", token, 3) == 0) {
+                        token = strsep(&dup, &delim);
+                        if (token != NULL) {
+                            int ret = -1;
+                            if (mraa_atoi(token, &ret) == MRAA_SUCCESS) {
+                                return ret;
+                            }
+                            return -1;
+                        }
+                    }
+                }
+                free(namelist[n]);
+            }
+            free(namelist);
+        }
+    }
+    return -1;
+}
+
 int
 mraa_find_i2c_bus(const char* devname, int startfrom)
 {