Re: [82/86] drm/i915: Move custom hotplug code into separate callback

[Sui Jingfeng <sui.jingfeng@linux.dev>]

Hi, Thomas


I love your patch, yet ...


On 2024/8/16 20:23, Thomas Zimmermann wrote:
> i915's fbdev contains additional code for hotplugging a display that
> cannot be ported to the common fbdev client. Introduce the callback
> struct drm_fb_helper.fb_hotplug and implement it for i915. The fbdev
> helpers invoke the callback before handing the hotplug event.
>
> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
> Cc: Jani Nikula <jani.nikula@linux.intel.com>
> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> Cc: Tvrtko Ursulin <tursulin@ursulin.net>
> Cc: Lucas De Marchi <lucas.demarchi@intel.com>
> Cc: "Thomas Hellström" <thomas.hellstrom@linux.intel.com>
> ---
>   drivers/gpu/drm/drm_fb_helper.c            |  6 +++
>   drivers/gpu/drm/i915/display/intel_fbdev.c | 43 ++++++++++++----------
>   include/drm/drm_fb_helper.h                | 13 +++++++
>   3 files changed, 42 insertions(+), 20 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> index d9e539b0fd1a..92926cb02dfb 100644
> --- a/drivers/gpu/drm/drm_fb_helper.c
> +++ b/drivers/gpu/drm/drm_fb_helper.c
> @@ -1938,6 +1938,12 @@ int drm_fb_helper_hotplug_event(struct drm_fb_helper *fb_helper)
>   	if (!drm_fbdev_emulation || !fb_helper)
>   		return 0;
>   
> +	if (fb_helper->funcs->fb_hotplug) {

We seems need to check the existence on the 'fb_helper->funcs' here,

For example:


if (fb_helper->funcs && fb_helper->funcs->fb_hotplug) {

Otherwise, it will de-reference NULL pointer.
Can be observed on a trivial driver though,
with no monitor(display) connected.


> +		err = fb_helper->funcs->fb_hotplug(fb_helper);
> +		if (err)
> +			return err;
> +	}
> +
>   	mutex_lock(&fb_helper->lock);
>   	if (fb_helper->deferred_setup) {
>   		err = __drm_fb_helper_initial_config_and_unlock(fb_helper);
> diff --git a/drivers/gpu/drm/i915/display/intel_fbdev.c b/drivers/gpu/drm/i915/display/intel_fbdev.c
> index c03fb00002a4..abe77ef0bd84 100644
> --- a/drivers/gpu/drm/i915/display/intel_fbdev.c
> +++ b/drivers/gpu/drm/i915/display/intel_fbdev.c
> @@ -305,10 +305,32 @@ static void intelfb_restore(struct drm_fb_helper *fb_helper)
>   	intel_fbdev_invalidate(ifbdev);
>   }
>   
> +static int intelfb_hotplug(struct drm_fb_helper *fb_helper)
> +{
> +	struct drm_device *dev = fb_helper->client.dev;
> +	struct drm_i915_private *dev_priv = to_i915(dev);
> +	struct intel_fbdev *ifbdev = dev_priv->display.fbdev.fbdev;
> +	bool send_hpd;
> +
> +	if (!ifbdev)
> +		return -EINVAL;
> +
> +	mutex_lock(&ifbdev->hpd_lock);
> +	send_hpd = !ifbdev->hpd_suspended;
> +	ifbdev->hpd_waiting = true;
> +	mutex_unlock(&ifbdev->hpd_lock);
> +
> +	if (!send_hpd || !(ifbdev->vma || dev->fb_helper->deferred_setup))
> +		return -EAGAIN;
> +
> +	return 0;
> +}
> +
>   static const struct drm_fb_helper_funcs intel_fb_helper_funcs = {
>   	.fb_probe = intelfb_create,
>   	.fb_dirty = intelfb_dirty,
>   	.fb_restore = intelfb_restore,
> +	.fb_hotplug = intelfb_hotplug,
>   };
>   
>   /*
> @@ -557,25 +579,6 @@ void intel_fbdev_set_suspend(struct drm_device *dev, int state, bool synchronous
>   	intel_fbdev_hpd_set_suspend(dev_priv, state);
>   }
>   
> -static int intel_fbdev_output_poll_changed(struct drm_device *dev)
> -{
> -	struct intel_fbdev *ifbdev = to_i915(dev)->display.fbdev.fbdev;
> -	bool send_hpd;
> -
> -	if (!ifbdev)
> -		return -EINVAL;
> -
> -	mutex_lock(&ifbdev->hpd_lock);
> -	send_hpd = !ifbdev->hpd_suspended;
> -	ifbdev->hpd_waiting = true;
> -	mutex_unlock(&ifbdev->hpd_lock);
> -
> -	if (send_hpd && (ifbdev->vma || dev->fb_helper->deferred_setup))
> -		drm_fb_helper_hotplug_event(dev->fb_helper);
> -
> -	return 0;
> -}
> -
>   static int intel_fbdev_restore_mode(struct drm_i915_private *dev_priv)
>   {
>   	struct intel_fbdev *ifbdev = dev_priv->display.fbdev.fbdev;
> @@ -637,7 +640,7 @@ static int intel_fbdev_client_hotplug(struct drm_client_dev *client)
>   	int ret;
>   
>   	if (dev->fb_helper)
> -		return intel_fbdev_output_poll_changed(dev);
> +		return drm_fb_helper_hotplug_event(fb_helper);
>   
>   	ret = drm_fb_helper_init(dev, fb_helper);
>   	if (ret)
> diff --git a/include/drm/drm_fb_helper.h b/include/drm/drm_fb_helper.h
> index 34eb77c18a13..3dcb9a60e408 100644
> --- a/include/drm/drm_fb_helper.h
> +++ b/include/drm/drm_fb_helper.h
> @@ -112,6 +112,19 @@ struct drm_fb_helper_funcs {
>   	 * TODO: Fix i915 to not require this callback.
>   	 */
>   	void (*fb_restore)(struct drm_fb_helper *helper);
> +
> +	/**
> +	 * @fb_hotplug:
> +	 *
> +	 * Driver callback to prepare hotplug event. If set, fbdev
> +	 * emulation will invoke this callback before sending a hotplug
> +	 * event.
> +	 *
> +	 * Only for i915. Do not use in new code.
> +	 *
> +	 * TODO: Fix i915 to not require this callback.
> +	 */
> +	int (*fb_hotplug)(struct drm_fb_helper *helper);
>   };
>   
>   /**

-- 
Best regards,
Sui