Re: [PATCH v4 1/1] drm/fb-helper: implement ioctl FBIO_WAITFORVSYNC

[Daniel Vetter]

On Tue, Feb 28, 2017 at 04:36:51PM +0100, Maxime Ripard wrote:
> Implement legacy framebuffer ioctl FBIO_WAITFORVSYNC in the generic
> framebuffer emulation driver. Legacy framebuffer users like non kms/drm
> based OpenGL(ES)/EGL implementations may require the ioctl to
> synchronize drawing or buffer flip for double buffering. It is tested on
> the i.MX6.
> 
> Signed-off-by: Maxime Ripard <maxime.ripard@xxxxxxxxxxxxxxxxxx>
> Tested-by: Neil Armstrong <narmstrong@xxxxxxxxxxxx>

Pushed to drm-misc, thanks.
-Daniel

> ---
>  drivers/gpu/drm/drm_fb_helper.c | 68 ++++++++++++++++++++++++++++++++++-
>  include/drm/drm_fb_helper.h     | 12 +++++-
>  2 files changed, 79 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> index c6de87abaca8..8ac8716c023a 100644
> --- a/drivers/gpu/drm/drm_fb_helper.c
> +++ b/drivers/gpu/drm/drm_fb_helper.c
> @@ -1240,6 +1240,74 @@ int drm_fb_helper_setcmap(struct fb_cmap *cmap, struct fb_info *info)
>  EXPORT_SYMBOL(drm_fb_helper_setcmap);
>  
>  /**
> + * drm_fb_helper_ioctl - legacy ioctl implementation
> + * @info: fbdev registered by the helper
> + * @cmd: ioctl command
> + * @arg: ioctl argument
> + *
> + * A helper to implement the standard fbdev ioctl. Only
> + * FBIO_WAITFORVSYNC is implemented for now.
> + */
> +int drm_fb_helper_ioctl(struct fb_info *info, unsigned int cmd,
> +			unsigned long arg)
> +{
> +	struct drm_fb_helper *fb_helper = info->par;
> +	struct drm_device *dev = fb_helper->dev;
> +	struct drm_mode_set *mode_set;
> +	struct drm_crtc *crtc;
> +	int ret = 0;
> +
> +	mutex_lock(&dev->mode_config.mutex);
> +	if (!drm_fb_helper_is_bound(fb_helper)) {
> +		ret = -EBUSY;
> +		goto unlock;
> +	}
> +
> +	switch (cmd) {
> +	case FBIO_WAITFORVSYNC:
> +		/*
> +		 * Only consider the first CRTC.
> +		 *
> +		 * This ioctl is supposed to take the CRTC number as
> +		 * an argument, but in fbdev times, what that number
> +		 * was supposed to be was quite unclear, different
> +		 * drivers were passing that argument differently
> +		 * (some by reference, some by value), and most of the
> +		 * userspace applications were just hardcoding 0 as an
> +		 * argument.
> +		 *
> +		 * The first CRTC should be the integrated panel on
> +		 * most drivers, so this is the best choice we can
> +		 * make. If we're not smart enough here, one should
> +		 * just consider switch the userspace to KMS.
> +		 */
> +		mode_set = &fb_helper->crtc_info[0].mode_set;
> +		crtc = mode_set->crtc;
> +
> +		/*
> +		 * Only wait for a vblank event if the CRTC is
> +		 * enabled, otherwise just don't do anythintg,
> +		 * not even report an error.
> +		 */
> +		ret = drm_crtc_vblank_get(crtc);
> +		if (!ret) {
> +			drm_crtc_wait_one_vblank(crtc);
> +			drm_crtc_vblank_put(crtc);
> +		}
> +
> +		ret = 0;
> +		goto unlock;
> +	default:
> +		ret = -ENOTTY;
> +	}
> +
> +unlock:
> +	mutex_unlock(&dev->mode_config.mutex);
> +	return ret;
> +}
> +EXPORT_SYMBOL(drm_fb_helper_ioctl);
> +
> +/**
>   * drm_fb_helper_check_var - implementation for ->fb_check_var
>   * @var: screeninfo to check
>   * @info: fbdev registered by the helper
> diff --git a/include/drm/drm_fb_helper.h b/include/drm/drm_fb_helper.h
> index 975deedd593e..2891888c6e41 100644
> --- a/include/drm/drm_fb_helper.h
> +++ b/include/drm/drm_fb_helper.h
> @@ -230,7 +230,8 @@ struct drm_fb_helper {
>  	.fb_blank	= drm_fb_helper_blank, \
>  	.fb_pan_display	= drm_fb_helper_pan_display, \
>  	.fb_debug_enter = drm_fb_helper_debug_enter, \
> -	.fb_debug_leave = drm_fb_helper_debug_leave
> +	.fb_debug_leave = drm_fb_helper_debug_leave, \
> +	.fb_ioctl	= drm_fb_helper_ioctl
>  
>  #ifdef CONFIG_DRM_FBDEV_EMULATION
>  void drm_fb_helper_prepare(struct drm_device *dev, struct drm_fb_helper *helper,
> @@ -286,6 +287,9 @@ void drm_fb_helper_set_suspend_unlocked(struct drm_fb_helper *fb_helper,
>  
>  int drm_fb_helper_setcmap(struct fb_cmap *cmap, struct fb_info *info);
>  
> +int drm_fb_helper_ioctl(struct fb_info *info, unsigned int cmd,
> +			unsigned long arg);
> +
>  int drm_fb_helper_hotplug_event(struct drm_fb_helper *fb_helper);
>  int drm_fb_helper_initial_config(struct drm_fb_helper *fb_helper, int bpp_sel);
>  int drm_fb_helper_single_add_all_connectors(struct drm_fb_helper *fb_helper);
> @@ -377,6 +381,12 @@ static inline int drm_fb_helper_setcmap(struct fb_cmap *cmap,
>  	return 0;
>  }
>  
> +static inline int drm_fb_helper_ioctl(struct fb_info *info, unsigned int cmd,
> +				      unsigned long arg)
> +{
> +	return 0;
> +}
> +
>  static inline void drm_fb_helper_unlink_fbi(struct drm_fb_helper *fb_helper)
>  {
>  }
> -- 
> git-series 0.8.11
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch