[PATCH 2/7] drm/fb-helper: Add drm_fb_helper_fbdev_setup/teardown()

[Noralf Trønnes]

Den 14.12.2017 21.19, skrev Daniel Vetter:
> On Thu, Dec 14, 2017 at 08:10:03PM +0100, Noralf Trønnes wrote:
>> Add helpers to setup and teardown fbdev emulation.
>>
>> Signed-off-by: Noralf Trønnes <noralf at tronnes.org>
>> ---
>>   drivers/gpu/drm/drm_fb_helper.c | 106 ++++++++++++++++++++++++++++++++++++++++
>>   include/drm/drm_fb_helper.h     |  25 ++++++++++
>>   2 files changed, 131 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
>> index 04a3a5ce370a..823fc8f50d85 100644
>> --- a/drivers/gpu/drm/drm_fb_helper.c
>> +++ b/drivers/gpu/drm/drm_fb_helper.c
>> @@ -2729,6 +2729,112 @@ int drm_fb_helper_hotplug_event(struct drm_fb_helper *fb_helper)
>>   }
>>   EXPORT_SYMBOL(drm_fb_helper_hotplug_event);
>>   
>> +/**
>> + * drm_fb_helper_fbdev_setup() - Setup fbdev emulation
>> + * @dev: DRM device
>> + * @fb_helper: fbdev helper structure to set up
>> + * @funcs: fbdev helper functions
>> + * @preferred_bpp: Preferred bits per pixel for the device.
>> + *                 @dev->mode_config.preferred_depth is used if this is zero.
>> + * @max_conn_count: Maximum number of connectors.
>> + *                  @dev->mode_config.num_connector is used if this is zero.
>> + *
>> + * This function sets up fbdev emulation and registers fbdev for access by
>> + * userspace. If all connectors are disconnected, setup is deferred to the next
>> + * time drm_fb_helper_hotplug_event() is called.
>> + * The caller must to provide a &drm_fb_helper_funcs->fb_probe callback
>> + * function.
> I think we should be a bit clearer when it's not advisable to use this
> helper because there are issues:
> - when connectors can be hotplugged (e.g. dp mst). For that case you need
>    to init the fbdev before you enabling hotplugging, but call
>    initial_config after you've enabled hotplugging. Otherwise there's a
>    posssible race window.

I have made a propose DOC change in patch 4.

> - when there's anything else that mus be done before we do the fbdev
>    registration, e.g. defio_init.

This happens in .fb_probe callback. See my reply to patch 5.

> So still not 100% sure this will help you all that much, but it's also not
> an unreasonable idea.
>
> Assuming we can agree on the ceveats and how do document them:
>
> Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>
>
>> + *
>> + * See also: drm_fb_helper_initial_config()
>> + *
>> + * Returns:
>> + * Zero on success or negative error code on failure.
>> + */
>> +int drm_fb_helper_fbdev_setup(struct drm_device *dev,
>> +			      struct drm_fb_helper *fb_helper,
>> +			      const struct drm_fb_helper_funcs *funcs,
>> +			      unsigned int preferred_bpp,
>> +			      unsigned int max_conn_count)
>> +{
>> +	int ret;
>> +
>> +	if (!preferred_bpp)
>> +		preferred_bpp = dev->mode_config.preferred_depth;
>> +	if (!preferred_bpp)
>> +		preferred_bpp = 32;
>> +
>> +	if (!max_conn_count)
>> +		max_conn_count = dev->mode_config.num_connector;
>> +	if (!max_conn_count) {
>> +		DRM_DEV_ERROR(dev->dev, "No connectors\n");
>> +		return -EINVAL;
>> +	}
>> +
>> +	drm_fb_helper_prepare(dev, fb_helper, funcs);
>> +
>> +	ret = drm_fb_helper_init(dev, fb_helper, max_conn_count);
>> +	if (ret < 0) {
>> +		DRM_DEV_ERROR(dev->dev, "Failed to initialize fbdev helper\n");
>> +		return ret;
>> +	}
>> +
>> +	ret = drm_fb_helper_single_add_all_connectors(fb_helper);
>> +	if (ret < 0) {
>> +		DRM_DEV_ERROR(dev->dev, "Failed to add connectors\n");
>> +		goto err_drm_fb_helper_fini;
>> +	}
>> +
>> +	if (!drm_drv_uses_atomic_modeset(dev))
>> +		drm_helper_disable_unused_functions(dev);
>> +
>> +	ret = drm_fb_helper_initial_config(fb_helper, preferred_bpp);
>> +	if (ret < 0) {
>> +		DRM_DEV_ERROR(dev->dev, "Failed to set fbdev configuration\n");
>> +		goto err_drm_fb_helper_fini;
>> +	}
>> +
>> +	return 0;
>> +
>> +err_drm_fb_helper_fini:
>> +	drm_fb_helper_fini(fb_helper);
>> +
>> +	return ret;
>> +}
>> +EXPORT_SYMBOL(drm_fb_helper_fbdev_setup);
>> +
>> +/**
>> + * drm_fb_helper_fbdev_teardown - Tear down fbdev emulation
>> + * @dev: DRM device
>> + *
>> + * This function unregisters fbdev if not already done and cleans up the
>> + * associated resources including the &drm_framebuffer.
>> + * The driver is responsible for freeing the &drm_fb_helper structure which is
>> + * stored in &drm_device->fb_helper. Do note that this pointer has been cleared
>> + * when this function returns.
>> + *
>> + * In order to support device removal/unplug while file handles are still open,
>> + * drm_fb_helper_unregister_fbi() should be called on device removal and
>> + * drm_fb_helper_fbdev_teardown() in the &drm_driver->release callback when
>> + * file handles are closed.
>> + */
>> +void drm_fb_helper_fbdev_teardown(struct drm_device *dev)
>> +{
>> +	struct drm_fb_helper *fb_helper = dev->fb_helper;
>> +
>> +	if (!fb_helper)
>> +		return;
>> +
>> +	/* Unregister if it hasn't been done already */
>> +	if (fb_helper->fbdev && fb_helper->fbdev->dev)
>> +		drm_fb_helper_unregister_fbi(fb_helper);
>> +
>> +	drm_fb_helper_fini(fb_helper);
>> +
>> +	if (fb_helper->fb)
>> +		drm_framebuffer_remove(fb_helper->fb);
>> +}
>> +EXPORT_SYMBOL(drm_fb_helper_fbdev_teardown);
>> +
>>   /**
>>    * drm_fb_helper_lastclose - DRM driver lastclose helper for fbdev emulation
>>    * @dev: DRM device
>> diff --git a/include/drm/drm_fb_helper.h b/include/drm/drm_fb_helper.h
>> index 1bd624579db7..aa78ac3b8ad0 100644
>> --- a/include/drm/drm_fb_helper.h
>> +++ b/include/drm/drm_fb_helper.h
>> @@ -320,6 +320,13 @@ int drm_fb_helper_add_one_connector(struct drm_fb_helper *fb_helper, struct drm_
>>   int drm_fb_helper_remove_one_connector(struct drm_fb_helper *fb_helper,
>>   				       struct drm_connector *connector);
>>   
>> +int drm_fb_helper_fbdev_setup(struct drm_device *dev,
>> +			      struct drm_fb_helper *fb_helper,
>> +			      const struct drm_fb_helper_funcs *funcs,
>> +			      unsigned int preferred_bpp,
>> +			      unsigned int max_conn_count);
>> +void drm_fb_helper_fbdev_teardown(struct drm_device *dev);
>> +
>>   void drm_fb_helper_lastclose(struct drm_device *dev);
>>   void drm_fb_helper_output_poll_changed(struct drm_device *dev);
>>   #else
>> @@ -525,6 +532,24 @@ drm_fb_helper_remove_one_connector(struct drm_fb_helper *fb_helper,
>>   	return 0;
>>   }
>>   
>> +static inline int
>> +drm_fb_helper_fbdev_setup(struct drm_device *dev,
>> +			  struct drm_fb_helper *fb_helper,
>> +			  const struct drm_fb_helper_funcs *funcs,
>> +			  unsigned int preferred_bpp,
>> +			  unsigned int max_conn_count)
>> +{
>> +	/* So drivers can use it to free the struct */
>> +	dev->fb_helper = fb_helper;
>> +
>> +	return 0;
>> +}
>> +
>> +static inline void drm_fb_helper_fbdev_teardown(struct drm_device *dev)
>> +{
>> +	dev->fb_helper = NULL;
>> +}
>> +
>>   static inline void drm_fb_helper_lastclose(struct drm_device *dev)
>>   {
>>   }
>> -- 
>> 2.14.2
>>