Re: [PATCH v2 02/21] drm: Add a callback from connector registering

[Daniel Vetter <daniel@ffwll.ch>]

On Mon, May 30, 2016 at 09:38:20AM +0100, Chris Wilson wrote:
> If a driver wants to more precisely control its initialisation and in
> particular, defer registering its interfaces with userspace until after
> everything is setup, it also needs to defer registering the connectors.
> As some devices need more work during registration, add a callback so
> that drivers can do additional work if required for a connector.
> 
> Correspondingly, we also require an unregister callback.
> 
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> Cc: dri-devel@lists.freedesktop.org

tbh I'd call these hooks simply register/unregister. There shouldn't be
any need for ordering every with interface registration/unregistartion,
assuming drivers don't fumble things.

Besides naming&kerneldoc (see below) lgtm as an idea.
-Daniel

> ---
>  drivers/gpu/drm/drm_crtc.c | 18 ++++++++++++++++--
>  include/drm/drm_crtc.h     | 25 +++++++++++++++++++++++++
>  2 files changed, 41 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
> index d2a6d958ca76..81641544ac3e 100644
> --- a/drivers/gpu/drm/drm_crtc.c
> +++ b/drivers/gpu/drm/drm_crtc.c
> @@ -1036,13 +1036,24 @@ int drm_connector_register(struct drm_connector *connector)
>  
>  	ret = drm_debugfs_connector_add(connector);
>  	if (ret) {
> -		drm_sysfs_connector_remove(connector);
> -		return ret;
> +		goto err_sysfs;
> +	}
> +
> +	if (connector->funcs->late_register) {
> +		ret = connector->funcs->late_register(connector);
> +		if (ret)
> +			goto err_debugfs;
>  	}
>  
>  	drm_mode_object_register(connector->dev, &connector->base);
>  
>  	return 0;
> +
> +err_debugfs:
> +	drm_debugfs_connector_remove(connector);
> +err_sysfs:
> +	drm_sysfs_connector_remove(connector);
> +	return ret;
>  }
>  EXPORT_SYMBOL(drm_connector_register);
>  
> @@ -1054,6 +1065,9 @@ EXPORT_SYMBOL(drm_connector_register);
>   */
>  void drm_connector_unregister(struct drm_connector *connector)
>  {
> +	if (connector->funcs->early_unregister)
> +		connector->funcs->early_unregister(connector);
> +
>  	drm_sysfs_connector_remove(connector);
>  	drm_debugfs_connector_remove(connector);
>  }
> diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
> index d1559cd04e3d..77b775cff4e7 100644
> --- a/include/drm/drm_crtc.h
> +++ b/include/drm/drm_crtc.h
> @@ -926,6 +926,31 @@ struct drm_connector_funcs {
>  			     uint64_t val);
>  
>  	/**
> +	 * @late_register:
> +	 *
> +	 * Register the connector with userspace, called from
> +	 * drm_connector_register. This should be called after driver
> +	 * load during its registration phase. All actions such as registering
> +	 * with auxiliary devices (such as drm_dp_aux_register) should be done
> +	 * during this callback. A simple guideline is that everything added
> +	 * from this callback should be removed during early_unregister (and
> +	 * vice versa).

Slight bikeshedding of the kerneldoc:

"This optional hook can be used to register additional userspace
interfaces attached to the connector, like backlight control, i2c, dp aux
or similar interfaces. It is called from drm_connector_register() when
registering all the core drm connector interfaces. Everything added from
this callback should be unregistered in the unregister() callback.

"Returns:

"0 on success or a negative failure code on error."

Similar bikeshed with unregister, i.e. state that it is optional, and that
is just to unregister additional interfaces.
> +	 *
> +	 */
> +	int (*late_register)(struct drm_connector *connector);
> +
> +	/**
> +	 * @early_unregister:
> +	 *
> +	 * Unregister the connector with userspace, called from
> +	 * drm_connector_unregister. This is called early in the driver

Please add () to drm_connector_unregister() so you end up with a hyperlink.

> +	 * unload sequence to disable userspace access before data
> +	 * structures are torndown.  A simple guideline is that this callback
> +	 * should remove everything added during late_register (and vice versa).
> +	 */
> +	void (*early_unregister)(struct drm_connector *connector);
> +
> +	/**
>  	 * @destroy:
>  	 *
>  	 * Clean up connector resources. This is called at driver unload time
> -- 
> 2.8.1
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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