diff options
| -rw-r--r-- | drivers/gpu/drm/drm_probe_helper.c | 49 |
1 files changed, 37 insertions, 12 deletions
diff --git a/drivers/gpu/drm/drm_probe_helper.c b/drivers/gpu/drm/drm_probe_helper.c index 13d178e6981b..e714b5a7955f 100644 --- a/drivers/gpu/drm/drm_probe_helper.c +++ b/drivers/gpu/drm/drm_probe_helper.c @@ -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 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. - * - * 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. + * The basic procedure is as follows + * + * 1. All modes currently on the connector's modes list are marked as stale + * + * 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. |