adc drivers: add comments

diff --git a/include/linux/adc.h b/include/linux/adc.h
index 90e44913dae7ca04e09a233cfdf82b4331529d89..be4547b038c411b8ea0febeaa1ff7a176ce31e70 100755 (executable)
--- a/include/linux/adc.h
+++ b/include/linux/adc.h
@@ -41,8 +41,19 @@ struct adc_client *adc_register(int chn,
                                void (*callback)(struct adc_client *, void *, int), \r
                                void *callback_param);\r
 void adc_unregister(struct adc_client *client);\r
-\r
+/*\r
+ * function: adc_sync_read\r
+ * 1)return value:\r
+ *     if correct, return adc sample value;\r
+ *     if error, return negative;\r
+ */\r
 int adc_sync_read(struct adc_client *client);\r
+/*\r
+ * function: adc_async_read\r
+ * 1)return value: if error, return negative; else return 0;\r
+ * 2)adc sample value: the third parameter of callback.\r
+ *     if timeout, sample value is -1; else sample value is non-negative\r
+ */\r
 int adc_async_read(struct adc_client *client);\r
 #else\r
 static inline struct adc_client *adc_register(int chn,\r