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drm: Expand the drm_helper_probe_single_connector_modes() docs

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Describe the procedure that drm_helper_probe_single_connector_modes()
uses to do it's work in the kernel-doc comment.

Caveat: Looks like crap and trying to reverse engineer the documentation
tools is not something I want to do.

Suggested-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1449782037-19722-3-git-send-email-ville.syrjala@linux.intel.com
This commit is contained in:
Ville Syrjälä 2015-12-10 23:13:57 +02:00 committed by Daniel Vetter
parent 0e8578c996
commit 5dec293b24
1 changed files with 35 additions and 10 deletions
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45
drivers/gpu/drm/drm_probe_helper.c
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@ -144,18 +144,43 @@ EXPORT_SYMBOL(drm_kms_helper_poll_enable_locked);
* @connector vfunc for drivers that use the CRTC helpers for output mode
* filtering and detection.
*
* If the helper operation returns no mode, and if the connector status is
* connector_status_connected, standard VESA DMT modes up to 1024x768 are
* automatically added to the modes list by a call to
* drm_add_modes_noedid().
* The basic procedure is as follows
*
* The function then filters out modes larger than @maxX and maxY if specified.
* It finally calls the optional connector ->mode_valid() helper operation for each
* mode in the probed list to check whether the mode is valid for the connector.
* 1. All modes currently on the connector's modes list are marked as stale
*
* Compared to drm_helper_probe_single_connector_modes_nomerge() this function
* merged the mode bits for the preferred mode, as a hack to work around some
* quirky issues on funky hardware.
* 2. New modes are added to the connector's probed_modes list with
* drm_mode_probed_add(). New modes start their life with status as OK.
* Modes are added from a single source using the following priority order.
*
* - debugfs 'override_edid' (used for testing only)
* - firmware EDID (drm_load_edid_firmware())
* - connector helper ->get_modes() vfunc
* - if the connector status is connector_status_connected, standard
* VESA DMT modes up to 1024x768 are automatically added
* (drm_add_modes_noedid())
*
* Finally modes specified via the kernel command line (video=...) are
* added in addition to what the earlier probes produced
* (drm_helper_probe_add_cmdline_mode()). These modes are generated
* using the VESA GTF/CVT formulas.
*
* 3. Modes are moved from the probed_modes list to the modes list. Potential
* duplicates are merged together (see drm_mode_connector_list_update()).
* After this step the probed_modes list will be empty again.
*
* 4. Any non-stale mode on the modes list then undergoes validation
*
* - drm_mode_validate_basic() performs basic sanity checks
* - drm_mode_validate_size() filters out modes larger than @maxX and @maxY
* (if specified)
* - drm_mode_validate_flag() checks the modes againt basic connector
* capabilites (interlace_allowed,doublescan_allowed,stereo_allowed)
* - the optional connector ->mode_valid() helper can perform driver and/or
* hardware specific checks
*
* 5. Any mode whose status is not OK is pruned from the connector's modes list,
* accompanied by a debug message indicating the reason for the mode's
* rejection (see drm_mode_prune_invalid()).
*
* Returns:
* The number of modes found on @connector.