diff options
| -rw-r--r-- | drivers/gpu/drm/drm_dp_helper.c | 45 |
1 files changed, 32 insertions, 13 deletions
diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c index ad73d7264743..9f66153a3c55 100644 --- a/drivers/gpu/drm/drm_dp_helper.c +++ b/drivers/gpu/drm/drm_dp_helper.c @@ -1728,10 +1728,18 @@ EXPORT_SYMBOL(drm_dp_remote_aux_init); * drm_dp_aux_init() - minimally initialise an aux channel * @aux: DisplayPort AUX channel * - * If you need to use the drm_dp_aux's i2c adapter prior to registering it - * with the outside world, call drm_dp_aux_init() first. You must still - * call drm_dp_aux_register() once the connector has been registered to - * allow userspace access to the auxiliary DP channel. + * If you need to use the drm_dp_aux's i2c adapter prior to registering it with + * the outside world, call drm_dp_aux_init() first. For drivers which are + * grandparents to their AUX adapters (e.g. the AUX adapter is parented by a + * &drm_connector), you must still call drm_dp_aux_register() once the connector + * has been registered to allow userspace access to the auxiliary DP channel. + * Likewise, for such drivers you should also assign &drm_dp_aux.drm_dev as + * early as possible so that the &drm_device that corresponds to the AUX adapter + * may be mentioned in debugging output from the DRM DP helpers. + * + * For devices which use a separate platform device for their AUX adapters, this + * may be called as early as required by the driver. + * */ void drm_dp_aux_init(struct drm_dp_aux *aux) { @@ -1751,15 +1759,26 @@ EXPORT_SYMBOL(drm_dp_aux_init); * drm_dp_aux_register() - initialise and register aux channel * @aux: DisplayPort AUX channel * - * Automatically calls drm_dp_aux_init() if this hasn't been done yet. - * This should only be called when the underlying &struct drm_connector is - * initialiazed already. Therefore the best place to call this is from - * &drm_connector_funcs.late_register. Not that drivers which don't follow this - * will Oops when CONFIG_DRM_DP_AUX_CHARDEV is enabled. - * - * Drivers which need to use the aux channel before that point (e.g. at driver - * load time, before drm_dev_register() has been called) need to call - * drm_dp_aux_init(). + * Automatically calls drm_dp_aux_init() if this hasn't been done yet. This + * should only be called once the parent of @aux, &drm_dp_aux.dev, is + * initialized. For devices which are grandparents of their AUX channels, + * &drm_dp_aux.dev will typically be the &drm_connector &device which + * corresponds to @aux. For these devices, it's advised to call + * drm_dp_aux_register() in &drm_connector_funcs.late_register, and likewise to + * call drm_dp_aux_unregister() in &drm_connector_funcs.early_unregister. + * Functions which don't follow this will likely Oops when + * %CONFIG_DRM_DP_AUX_CHARDEV is enabled. + * + * For devices where the AUX channel is a device that exists independently of + * the &drm_device that uses it, such as SoCs and bridge devices, it is + * recommended to call drm_dp_aux_register() after a &drm_device has been + * assigned to &drm_dp_aux.drm_dev, and likewise to call + * drm_dp_aux_unregister() once the &drm_device should no longer be associated + * with the AUX channel (e.g. on bridge detach). + * + * Drivers which need to use the aux channel before either of the two points + * mentioned above need to call drm_dp_aux_init() in order to use the AUX + * channel before registration. * * Returns 0 on success or a negative error code on failure. */ |