diff --git a/include/camera/Camera.h b/include/camera/Camera.h
index e6d84ba..e734c38 100644
--- a/include/camera/Camera.h
+++ b/include/camera/Camera.h
@@ -105,8 +105,8 @@
 };
 
 enum {
-    CAMERA_FACING_BACK = 0,
-    CAMERA_FACING_FRONT = 1 /* The camera faces to the user */
+    CAMERA_FACING_BACK = 0, /* The facing of the camera is opposite to that of the screen. */
+    CAMERA_FACING_FRONT = 1 /* The facing of the camera is the same as that of the screen. */
 };
 
 struct CameraInfo {
@@ -122,10 +122,12 @@
      * camera image needs to be rotated clockwise so it shows correctly on
      * the display in its natural orientation. It should be 0, 90, 180, or 270.
      *
-     * For example, suppose a device has a naturally tall screen, but the camera
-     * sensor is mounted in landscape. If the top side of the camera sensor is
-     * aligned with the right edge of the display in natural orientation, the
-     * value should be 90.
+     * For example, suppose a device has a naturally tall screen. The
+     * back-facing camera sensor is mounted in landscape. You are looking at
+     * the screen. If the top side of the camera sensor is aligned with the
+     * right edge of the screen in natural orientation, the value should be
+     * 90. If the top side of a front-facing camera sensor is aligned with
+     * the right of the screen, the value should be 270.
      */
     int orientation;
 };
diff --git a/include/camera/CameraHardwareInterface.h b/include/camera/CameraHardwareInterface.h
index 6a66e3c..35c5aa1 100644
--- a/include/camera/CameraHardwareInterface.h
+++ b/include/camera/CameraHardwareInterface.h
@@ -190,7 +190,9 @@
      */
     virtual status_t    cancelPicture() = 0;
 
-    /** Set the camera parameters. */
+    /**
+     * Set the camera parameters. This returns BAD_VALUE if any parameter is
+     * invalid or not supported. */
     virtual status_t    setParameters(const CameraParameters& params) = 0;
 
     /** Return the camera parameters. */
diff --git a/include/camera/CameraParameters.h b/include/camera/CameraParameters.h
index 53039a0..4e770fd 100644
--- a/include/camera/CameraParameters.h
+++ b/include/camera/CameraParameters.h
@@ -142,16 +142,23 @@
     // the best.
     // Example value: "90". Read/write.
     static const char KEY_JPEG_QUALITY[];
-    // The orientation of the device in degrees. For example, suppose the
-    // natural position of the device is landscape. If the user takes a picture
-    // in landscape mode in 2048x1536 resolution, the rotation will be set to
-    // "0". If the user rotates the phone 90 degrees clockwise, the rotation
-    // should be set to "90".
-    // The camera driver can set orientation in the EXIF header without rotating
-    // the picture. Or the driver can rotate the picture and the EXIF thumbnail.
-    // If the Jpeg picture is rotated, the orientation in the EXIF header should
-    // be missing or 1 (row #0 is top and column #0 is left side). The driver
-    // should not set default value for this parameter.
+    // The rotation angle in degrees relative to the orientation of the camera.
+    // This affects the pictures returned from CAMERA_MSG_COMPRESSED_IMAGE. The
+    // camera driver may set orientation in the EXIF header without rotating the
+    // picture. Or the driver may rotate the picture and the EXIF thumbnail. If
+    // the Jpeg picture is rotated, the orientation in the EXIF header will be
+    // missing or 1 (row #0 is top and column #0 is left side).
+    //
+    // Note that the JPEG pictures of front-facing cameras are not mirrored
+    // as in preview display.
+    //
+    // For example, suppose the natural orientation of the device is portrait.
+    // The device is rotated 270 degrees clockwise, so the device orientation is
+    // 270. Suppose a back-facing camera sensor is mounted in landscape and the
+    // top side of the camera sensor is aligned with the right edge of the
+    // display in natural orientation. So the camera orientation is 90. The
+    // rotation should be set to 0 (270 + 90).
+    //
     // Example value: "0" or "90" or "180" or "270". Write only.
     static const char KEY_ROTATION[];
     // GPS latitude coordinate. GPSLatitude and GPSLatitudeRef will be stored in