3 files changed, 115 insertions, 65 deletions

diff --git a/Documentation/DocBook/drm.tmpl b/Documentation/DocBook/drm.tmpl
index 50af3298ac1f..4268cbe6f95c 100644
--- a/Documentation/DocBook/drm.tmpl
+++ b/Documentation/DocBook/drm.tmpl
@@ -965,6 +965,7 @@ int max_width, max_height;</synopsis>
     </itemizedlist>
     <sect2>
       <title>Display Modes Function Reference</title>
+!Iinclude/drm/drm_modes.h
 !Edrivers/gpu/drm/drm_modes.c
     </sect2>
     <sect2>
diff --git a/drivers/gpu/drm/drm_modes.c b/drivers/gpu/drm/drm_modes.c
index cc352eed0191..8b410576fce4 100644
--- a/drivers/gpu/drm/drm_modes.c
+++ b/drivers/gpu/drm/drm_modes.c
@@ -63,9 +63,10 @@ EXPORT_SYMBOL(drm_mode_debug_printmodeline);
  * drm_mode_create - create a new display mode
  * @dev: DRM device
  *
- * Create a new drm_display_mode, give it an ID, and return it.
+ * Create a new, cleared drm_display_mode with kzalloc, allocate an ID for it
+ * and return it.
  *
- * RETURNS:
+ * Returns:
  * Pointer to new mode on success, NULL on error.
  */
 struct drm_display_mode *drm_mode_create(struct drm_device *dev)
@@ -90,7 +91,7 @@ EXPORT_SYMBOL(drm_mode_create);
  * @dev: DRM device
  * @mode: mode to remove
  *
- * Free @mode's unique identifier, then free it.
+ * Release @mode's unique ID, then free it @mode structure itself using kfree.
  */
 void drm_mode_destroy(struct drm_device *dev, struct drm_display_mode *mode)
 {
@@ -104,11 +105,13 @@ void drm_mode_destroy(struct drm_device *dev, struct drm_display_mode *mode)
 EXPORT_SYMBOL(drm_mode_destroy);
 
 /**
- * drm_mode_probed_add - add a mode to a connector's probed mode list
+ * drm_mode_probed_add - add a mode to a connector's probed_mode list
  * @connector: connector the new mode
  * @mode: mode data
  *
- * Add @mode to @connector's mode list for later use.
+ * Add @mode to @connector's probed_mode list for later use. This list should
+ * then in a second step get filtered and all the modes actually supported by
+ * the hardware moved to the @connector's modes list.
  */
 void drm_mode_probed_add(struct drm_connector *connector,
                          struct drm_display_mode *mode)
@@ -120,16 +123,14 @@ void drm_mode_probed_add(struct drm_connector *connector,
 EXPORT_SYMBOL(drm_mode_probed_add);
 
 /**
- * drm_cvt_mode -create a modeline based on CVT algorithm
- * @dev: DRM device
+ * drm_cvt_mode -create a modeline based on the CVT algorithm
+ * @dev: drm device
  * @hdisplay: hdisplay size
  * @vdisplay: vdisplay size
- * @vrefresh  : vrefresh rate
- * @reduced : Whether the GTF calculation is simplified
- * @interlaced:Whether the interlace is supported
- * @margins: whether to add margins or not
- *
- * return the modeline based on CVT algorithm
+ * @vrefresh: vrefresh rate
+ * @reduced: whether to use reduced blanking
+ * @interlaced: whether to compute an interlaced mode
+ * @margins: whether to add margins (borders)
  *
  * This function is called to generate the modeline based on CVT algorithm
  * according to the hdisplay, vdisplay, vrefresh.
@@ -139,6 +140,11 @@ EXPORT_SYMBOL(drm_mode_probed_add);
  *
  * And it is copied from xf86CVTmode in xserver/hw/xfree86/modes/xf86cvt.c.
  * What I have done is to translate it by using integer calculation.
+ *
+ * Returns:
+ * The modeline based on the CVT algorithm stored in a drm_display_mode object.
+ * The display mode object is allocated with drm_mode_create(). Returns NULL
+ * when no mode could be allocated.
  */
 struct drm_display_mode *drm_cvt_mode(struct drm_device *dev, int hdisplay,
                                       int vdisplay, int vrefresh,
@@ -338,23 +344,25 @@ struct drm_display_mode *drm_cvt_mode(struct drm_device *dev, int hdisplay,
 EXPORT_SYMBOL(drm_cvt_mode);
 
 /**
- * drm_gtf_mode_complex - create the modeline based on full GTF algorithm
- *
- * @dev         :drm device
- * @hdisplay    :hdisplay size
- * @vdisplay    :vdisplay size
- * @vrefresh    :vrefresh rate.
- * @interlaced  :whether the interlace is supported
- * @margins     :desired margin size
+ * drm_gtf_mode_complex - create the modeline based on the full GTF algorithm
+ * @dev: drm device
+ * @hdisplay: hdisplay size
+ * @vdisplay: vdisplay size
+ * @vrefresh: vrefresh rate.
+ * @interlaced: whether to compute an interlaced mode
+ * @margins: desired margin (borders) size
  * @GTF_M: extended GTF formula parameters
  * @GTF_2C: extended GTF formula parameters
  * @GTF_K: extended GTF formula parameters
  * @GTF_2J: extended GTF formula parameters
  *
- * return the modeline based on full GTF algorithm.
- *
  * GTF feature blocks specify C and J in multiples of 0.5, so we pass them
  * in here multiplied by two.  For a C of 40, pass in 80.
+ *
+ * Returns:
+ * The modeline based on the full GTF algorithm stored in a drm_display_mode object.
+ * The display mode object is allocated with drm_mode_create(). Returns NULL
+ * when no mode could be allocated.
  */
 struct drm_display_mode *
 drm_gtf_mode_complex(struct drm_device *dev, int hdisplay, int vdisplay,
@@ -524,14 +532,13 @@ drm_gtf_mode_complex(struct drm_device *dev, int hdisplay, int vdisplay,
 EXPORT_SYMBOL(drm_gtf_mode_complex);
 
 /**
- * drm_gtf_mode - create the modeline based on GTF algorithm
- *
- * @dev         :drm device
- * @hdisplay    :hdisplay size
- * @vdisplay    :vdisplay size
- * @vrefresh    :vrefresh rate.
- * @interlaced  :whether the interlace is supported
- * @margins     :whether the margin is supported
+ * drm_gtf_mode - create the modeline based on the GTF algorithm
+ * @dev: drm device
+ * @hdisplay: hdisplay size
+ * @vdisplay: vdisplay size
+ * @vrefresh: vrefresh rate.
+ * @interlaced: whether to compute an interlaced mode
+ * @margins: desired margin (borders) size
  *
  * return the modeline based on GTF algorithm
  *
@@ -550,6 +557,11 @@ EXPORT_SYMBOL(drm_gtf_mode_complex);
  * C = 40
  * K = 128
  * J = 20
+ *
+ * Returns:
+ * The modeline based on the GTF algorithm stored in a drm_display_mode object.
+ * The display mode object is allocated with drm_mode_create(). Returns NULL
+ * when no mode could be allocated.
  */
 struct drm_display_mode *
 drm_gtf_mode(struct drm_device *dev, int hdisplay, int vdisplay, int vrefresh,
@@ -562,6 +574,13 @@ drm_gtf_mode(struct drm_device *dev, int hdisplay, int vdisplay, int vrefresh,
 EXPORT_SYMBOL(drm_gtf_mode);
 
 #ifdef CONFIG_VIDEOMODE_HELPERS
+/**
+ * drm_display_mode_from_videomode - fill in @dmode using @vm,
+ * @vm: videomode structure to use as source
+ * @dmode: drm_display_mode structure to use as destination
+ *
+ * Fills out @dmode using the display mode specified in @vm.
+ */
 void drm_display_mode_from_videomode(const struct videomode *vm,
                                      struct drm_display_mode *dmode)
 {
@@ -606,6 +625,9 @@ EXPORT_SYMBOL_GPL(drm_display_mode_from_videomode);
  * This function is expensive and should only be used, if only one mode is to be
  * read from DT. To get multiple modes start with of_get_display_timings and
  * work with that instead.
+ *
+ * Returns:
+ * 0 on success, a negative errno code when no of videomode node was found.
  */
 int of_get_drm_display_mode(struct device_node *np,
                             struct drm_display_mode *dmode, int index)
@@ -633,7 +655,8 @@ EXPORT_SYMBOL_GPL(of_get_drm_display_mode);
  * drm_mode_set_name - set the name on a mode
  * @mode: name will be set in this mode
  *
- * Set the name of @mode to a standard format.
+ * Set the name of @mode to a standard format which is <hdisplay>x<vdisplay>
+ * with an optional 'i' suffix for interlaced modes.
  */
 void drm_mode_set_name(struct drm_display_mode *mode)
 {
@@ -648,7 +671,9 @@ EXPORT_SYMBOL(drm_mode_set_name);
 /** drm_mode_hsync - get the hsync of a mode
  * @mode: mode
  *
- * Return @modes's hsync rate in kHz, rounded to the nearest int.
+ * Returns:
+ * @modes's hsync rate in kHz, rounded to the nearest integer. Calculates the
+ * value first if it is not yet set.
  */
 int drm_mode_hsync(const struct drm_display_mode *mode)
 {
@@ -672,14 +697,9 @@ EXPORT_SYMBOL(drm_mode_hsync);
  * drm_mode_vrefresh - get the vrefresh of a mode
  * @mode: mode
  *
- * Return @mode's vrefresh rate in Hz or calculate it if necessary.
- *
- * FIXME: why is this needed?  shouldn't vrefresh be set already?
- *
- * RETURNS:
- * Vertical refresh rate. It will be the result of actual value plus 0.5.
- * If it is 70.288, it will return 70Hz.
- * If it is 59.6, it will return 60Hz.
+ * Returns:
+ * @modes's vrefresh rate in Hz, rounded to the nearest integer. Calculates the
+ * value first if it is not yet set.
  */
 int drm_mode_vrefresh(const struct drm_display_mode *mode)
 {
@@ -708,11 +728,11 @@ int drm_mode_vrefresh(const struct drm_display_mode *mode)
 EXPORT_SYMBOL(drm_mode_vrefresh);
 
 /**
- * drm_mode_set_crtcinfo - set CRTC modesetting parameters
+ * drm_mode_set_crtcinfo - set CRTC modesetting timing parameters
  * @p: mode
  * @adjust_flags: a combination of adjustment flags
  *
- * Setup the CRTC modesetting parameters for @p, adjusting if necessary.
+ * Setup the CRTC modesetting timing parameters for @p, adjusting if necessary.
  *
  * - The CRTC_INTERLACE_HALVE_V flag can be used to halve vertical timings of
  *   interlaced modes.
@@ -780,7 +800,6 @@ void drm_mode_set_crtcinfo(struct drm_display_mode *p, int adjust_flags)
 }
 EXPORT_SYMBOL(drm_mode_set_crtcinfo);
 
-
 /**
  * drm_mode_copy - copy the mode
  * @dst: mode to overwrite
@@ -807,6 +826,9 @@ EXPORT_SYMBOL(drm_mode_copy);
  *
  * Just allocate a new mode, copy the existing mode into it, and return
  * a pointer to it.  Used to create new instances of established modes.
+ *
+ * Returns:
+ * Pointer to duplicated mode on success, NULL on error.
  */
 struct drm_display_mode *drm_mode_duplicate(struct drm_device *dev,
                                             const struct drm_display_mode *mode)
@@ -830,7 +852,7 @@ EXPORT_SYMBOL(drm_mode_duplicate);
  *
  * Check to see if @mode1 and @mode2 are equivalent.
  *
- * RETURNS:
+ * Returns:
  * True if the modes are equal, false otherwise.
  */
 bool drm_mode_equal(const struct drm_display_mode *mode1, const struct drm_display_mode *mode2)
@@ -859,7 +881,7 @@ EXPORT_SYMBOL(drm_mode_equal);
  * Check to see if @mode1 and @mode2 are equivalent, but
  * don't check the pixel clocks nor the stereo layout.
  *
- * RETURNS:
+ * Returns:
  * True if the modes are equal, false otherwise.
  */
 bool drm_mode_equal_no_clocks_no_stereo(const struct drm_display_mode *mode1,
@@ -890,9 +912,10 @@ EXPORT_SYMBOL(drm_mode_equal_no_clocks_no_stereo);
  * @maxX: maximum width
  * @maxY: maximum height
  *
- * The DRM device (@dev) has size and pitch limits.  Here we validate the
- * modes we probed for @dev against those limits and set their status as
- * necessary.
+ * This function is a helper which can be used to validate modes against size
+ * limitations of the DRM device/connector. If a mode is too big its status
+ * memeber is updated with the appropriate validation failure code. The list
+ * itself is not changed.
  */
 void drm_mode_validate_size(struct drm_device *dev,
                             struct list_head *mode_list,
@@ -916,9 +939,10 @@ EXPORT_SYMBOL(drm_mode_validate_size);
  * @mode_list: list of modes to check
  * @verbose: be verbose about it
  *
- * Once mode list generation is complete, a caller can use this routine to
- * remove invalid modes from a mode list.  If any of the modes have a
- * status other than %MODE_OK, they are removed from @mode_list and freed.
+ * This helper function can be used to prune a display mode list after
+ * validation has been completed. All modes who's status is not MODE_OK will be
+ * removed from the list, and if @verbose the status code and mode name is also
+ * printed to dmesg.
  */
 void drm_mode_prune_invalid(struct drm_device *dev,
                             struct list_head *mode_list, bool verbose)
@@ -948,7 +972,7 @@ EXPORT_SYMBOL(drm_mode_prune_invalid);
  * Compare two modes, given by @lh_a and @lh_b, returning a value indicating
  * which is better.
  *
- * RETURNS:
+ * Returns:
  * Negative if @lh_a is better than @lh_b, zero if they're equivalent, or
  * positive if @lh_b is better than @lh_a.
  */
@@ -976,9 +1000,9 @@ static int drm_mode_compare(void *priv, struct list_head *lh_a, struct list_head
 
 /**
  * drm_mode_sort - sort mode list
- * @mode_list: list to sort
+ * @mode_list: list of drm_display_mode structures to sort
  *
- * Sort @mode_list by favorability, putting good modes first.
+ * Sort @mode_list by favorability, moving good modes to the head of the list.
  */
 void drm_mode_sort(struct list_head *mode_list)
 {
@@ -992,8 +1016,10 @@ EXPORT_SYMBOL(drm_mode_sort);
  *
  * This moves the modes from the @connector probed_modes list
  * to the actual mode list. It compares the probed mode against the current
- * list and only adds different modes. All modes unverified after this point
- * will be removed by the prune invalid modes.
+ * list and only adds different/new modes.
+ *
+ * This is just a helper functions doesn't validate any modes itself and also
+ * doesn't prune any invalid modes. Callers need to do that themselves.
  */
 void drm_mode_connector_list_update(struct drm_connector *connector)
 {
@@ -1028,18 +1054,25 @@ void drm_mode_connector_list_update(struct drm_connector *connector)
 EXPORT_SYMBOL(drm_mode_connector_list_update);
 
 /**
- * drm_mode_parse_command_line_for_connector - parse command line for connector
- * @mode_option: per connector mode option
- * @connector: connector to parse line for
- * @mode: preallocated mode structure to fill out
+ * drm_mode_parse_command_line_for_connector - parse command line modeline for connector
+ * @mode_option: optional per connector mode option
+ * @connector: connector to parse modeline for
+ * @mode: preallocated drm_cmdline_mode structure to fill out
+ *
+ * This parses @mode_option command line modeline for modes and options to
+ * configure the connector. If @mode_option is NULL the default command line
+ * modeline in fb_mode_option will be parsed instead.
  *
- * This parses the connector specific then generic command lines for
- * modes and options to configure the connector.
+ * This uses the same parameters as the fb modedb.c, except for an extra
+ * force-enable, force-enable-digital and force-disable bit at the end:
  *
- * This uses the same parameters as the fb modedb.c, except for extra
  *      <xres>x<yres>[M][R][-<bpp>][@<refresh>][i][m][eDd]
  *
- * enable/enable Digital/disable bit at the end
+ * The intermediate drm_cmdline_mode structure is required to store additional
+ * options from the command line modline like the force-enabel/disable flag.
+ *
+ * Returns:
+ * True if a valid modeline has been parsed, false otherwise.
  */
 bool drm_mode_parse_command_line_for_connector(const char *mode_option,
                                                struct drm_connector *connector,
@@ -1192,6 +1225,14 @@ done:
 }
 EXPORT_SYMBOL(drm_mode_parse_command_line_for_connector);
 
+/**
+ * drm_mode_create_from_cmdline_mode - convert a command line modeline into a DRM display mode
+ * @dev: DRM device to create the new mode for
+ * @cmd: input command line modeline
+ *
+ * Returns:
+ * Pointer to converted mode on success, NULL on error.
+ */
 struct drm_display_mode *
 drm_mode_create_from_cmdline_mode(struct drm_device *dev,
                                   struct drm_cmdline_mode *cmd)
diff --git a/include/drm/drm_modes.h b/include/drm/drm_modes.h
index b3507f15d010..995c34d91ef1 100644
--- a/include/drm/drm_modes.h
+++ b/include/drm/drm_modes.h
@@ -162,6 +162,14 @@ struct drm_cmdline_mode {
         enum drm_connector_force force;
 };
 
+/**
+ * drm_mode_is_stereo - check for stereo mode flags
+ * @mode: drm_display_mode to check
+ *
+ * Returns:
+ * True if the mode is one of the stereo modes (like side-by-side), false if
+ * not.
+ */
 static inline bool drm_mode_is_stereo(const struct drm_display_mode *mode)
 {
         return mode->flags & DRM_MODE_FLAG_3D_MASK;