doc: Add fpi-dev-img section to the docs

doc/libfprint-docs.xml

@@ -40,6 +40,7 @@
     <title>Writing Drivers</title>
     <xi:include href="xml/fpi-log.xml"/>
     <xi:include href="xml/fpi-dev.xml"/>
+    <xi:include href="xml/fpi-dev-img.xml"/>
     <xi:include href="xml/fpi-core.xml"/>
     <xi:include href="xml/fpi-core-img.xml"/>
     <xi:include href="xml/fpi-ssm.xml"/>

doc/libfprint-sections.txt

@@ -197,6 +197,28 @@ fp_dev_set_instance_data
 FP_INSTANCE_DATA
 </SECTION>
 
+<SECTION>
+<INCLUDE>fpi-dev-img.h</INCLUDE>
+<FILE>fpi-dev-img</FILE>
+fp_imgdev_action
+fp_imgdev_state
+fp_imgdev_enroll_state
+fp_imgdev_verify_state
+
+fpi_imgdev_abort_scan
+fpi_imgdev_activate_complete
+fpi_imgdev_close_complete
+fpi_imgdev_deactivate_complete
+fpi_imgdev_get_action
+fpi_imgdev_get_action_result
+fpi_imgdev_get_action_state
+fpi_imgdev_image_captured
+fpi_imgdev_open_complete
+fpi_imgdev_report_finger_status
+fpi_imgdev_session_error
+fpi_imgdev_set_action_result
+</SECTION>
+
 <SECTION>
 <INCLUDE>fpi-core.h</INCLUDE>
 <FILE>fpi-core</FILE>

libfprint/fpi-dev-img.c

@@ -25,6 +25,15 @@
 #include "fpi-async.h"
 #include "fp_internal.h"
 
+/**
+ * SECTION:fpi-dev-img
+ * @title: Image device operations
+ *
+ * As drivers work through different operations, they need to report back
+ * to the core as to their internal state, so errors and successes can be
+ * reported back to front-ends.
+ */
+
 #define MIN_ACCEPTABLE_MINUTIAE 10
 #define BOZORTH3_DEFAULT_THRESHOLD 40
 #define IMG_ENROLL_STAGES 5