Re: [PATCH] drm: tda998x: mali-dp: hdlcd: refactor connector registration

[Brian Starkey <brian.starkey@arm.com>]

Hi Daniel,

On Mon, Oct 24, 2016 at 04:36:27PM +0200, Daniel Vetter wrote:
>On Mon, Oct 24, 2016 at 03:27:59PM +0100, Brian Starkey wrote:
>> Connectors shouldn't be registered until the rest of the whole device
>> is set up, so that consistent state is presented to userspace.
>>
>> As such, remove the calls to drm_connector_register() and
>> drm_connector_unregister() from tda998x, as these are now handled by
>> drm_dev_(un)register() itself.
>>
>> To work with this change, the mali-dp and hdlcd bind and unbind
>> sequences have to be reordered, to ensure that the componentised
>> encoder/connector is bound before drm_dev_register() registers all
>> connectors. Similarly, the device must be unregistered before the
>> component is unbound.
>>
>> Altogether, this allows other drivers using tda998x to be
>> de-midlayered, and to have less racy initialisation of their components.
>>
>> Splitting this commit into three (one per driver) isn't possible without
>> intermediate breakage, so it is all squashed together here.
>>
>> Suggested-by: Russell King <rmk+kernel@arm.linux.org.uk>
>> Signed-off-by: Brian Starkey <brian.starkey@arm.com>
>> Reviewed-by: Liviu Dudau <Liviu.Dudau@arm.com>
>
>> diff --git a/drivers/gpu/drm/i2c/tda998x_drv.c b/drivers/gpu/drm/i2c/tda998x_drv.c
>> index f4315bc..6e6fca2 100644
>> --- a/drivers/gpu/drm/i2c/tda998x_drv.c
>> +++ b/drivers/gpu/drm/i2c/tda998x_drv.c
>> @@ -1369,7 +1369,6 @@ const struct drm_connector_helper_funcs tda998x_connector_helper_funcs = {
>>
>>  static void tda998x_connector_destroy(struct drm_connector *connector)
>>  {
>> -	drm_connector_unregister(connector);
>>  	drm_connector_cleanup(connector);
>>  }
>>
>> @@ -1441,16 +1440,10 @@ static int tda998x_bind(struct device *dev, struct device *master, void *data)
>>  	if (ret)
>>  		goto err_connector;
>>
>> -	ret = drm_connector_register(&priv->connector);
>> -	if (ret)
>> -		goto err_sysfs;
>> -
>
>Instead of smashing all these patches into one, what about checking here
>for midlayer driver set with:
>
>	/* register here for drivers still using midlayer load/unload */
>	if (dev->driver->load)
>		drm_connector_register(connector),
>
>Similar in other places. That way we wouldn't need to switch the world in
>one patch.

I don't think that helps. If we do that in isolation (first), then
mali-dp and hdlcd won't get their connectors registered because their
bind order is:

	drm_dev_register();
	component_bind_all();

If we change the mali-dp/hdlcd bind order first, then tda998x will
explode on drm_connector_register() until it's patched to remove that.

As I mentioned in my mail to Russell, the only way I can see to avoid
patching all three drivers in one go is:
  1) Add (probably open-coded) drm_connector_register_all() to the end
     of bind in hdlcd and mali-dp
  2) Patch tda998x to remove drm_connector_register()
  3) Reorder hdlcd/mali-dp bind and remove the connector registration
     added in 1)

We can do that, but it's extra churn for the same result, and none of
the 5 patches will really make sense in isolation anyway.

Cheers,
-Brian

>-Daniel
>
>>  	drm_mode_connector_attach_encoder(&priv->connector, &priv->encoder);
>>
>>  	return 0;
>>
>> -err_sysfs:
>> -	drm_connector_cleanup(&priv->connector);
>>  err_connector:
>>  	drm_encoder_cleanup(&priv->encoder);
>>  err_encoder:
>> @@ -1463,7 +1456,6 @@ static void tda998x_unbind(struct device *dev, struct device *master,
>>  {
>>  	struct tda998x_priv *priv = dev_get_drvdata(dev);
>>
>> -	drm_connector_unregister(&priv->connector);
>>  	drm_connector_cleanup(&priv->connector);
>>  	drm_encoder_cleanup(&priv->encoder);
>>  	tda998x_destroy(priv);
>> --
>> 1.7.9.5
>>
>> _______________________________________________
>> dri-devel mailing list
>> dri-devel@lists.freedesktop.org
>> https://lists.freedesktop.org/mailman/listinfo/dri-devel
>
>-- 
>Daniel Vetter
>Software Engineer, Intel Corporation
>http://blog.ffwll.ch
>