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SubjectRe: [PATCH v2 2/2] drm/fb_helper: implement ioctl FBIO_WAITFORVSYNC
On Thu, Feb 02, 2017 at 11:31:57AM +0100, Maxime Ripard wrote:
> From: Stefan Christ <s.christ@phytec.de>
>
> 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.
>
> Code is based on
> https://github.com/Xilinx/linux-xlnx/blob/master/drivers/gpu/drm/xilinx/xilinx_drm_fb.c#L196
>
> Signed-off-by: Stefan Christ <s.christ@phytec.de>
> Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
> ---
> drivers/gpu/drm/drm_fb_helper.c | 55 ++++++++++++++++++++++++++++++++++-
> include/drm/drm_fb_helper.h | 5 ++-
> 2 files changed, 59 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> index e934b541feea..39a3532e311c 100644
> --- a/drivers/gpu/drm/drm_fb_helper.c
> +++ b/drivers/gpu/drm/drm_fb_helper.c
> @@ -1234,6 +1234,61 @@ 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;
> + unsigned int i;
> + int ret = 0;
> +
> + drm_modeset_lock_all(dev);
> + if (!drm_fb_helper_is_bound(fb_helper)) {
> + drm_modeset_unlock_all(dev);
> + return -EBUSY;
> + }
> +
> + switch (cmd) {
> + case FBIO_WAITFORVSYNC:
> + for (i = 0; i < fb_helper->crtc_count; i++) {

FBIO_WAITFORVSYNC takes the crtc as a parmeter, so I'm not sure we want
to do this for all the crtcs. Though what that crtc means for fb is
rather poorly defined.

> + struct drm_mode_set *mode_set;
> + struct drm_crtc *crtc;
> +
> + mode_set = &fb_helper->crtc_info[i].mode_set;
> + crtc = mode_set->crtc;
> +
> + /*
> + * Only call drm_crtc_wait_one_vblank for crtcs that
> + * are currently enabled.
> + */
> + if (!crtc->enabled)
> + continue;
> +
> + ret = drm_crtc_vblank_get(crtc);
> + if (!ret) {
> + drm_crtc_wait_one_vblank(crtc);
> + drm_crtc_vblank_put(crtc);
> + }

This looks quite sub-optimal. It should rather do something along the
lines of what drm_atomic_helper_wait_for_vblanks() does.

> + }
> + goto unlock;
> + default:
> + ret = -ENOTTY;
> + }
> +
> +unlock:
> + drm_modeset_unlock_all(dev);
> + 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..460be9d9fa98 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 +287,8 @@ 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);
> --
> git-series 0.8.11
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

--
Ville Syrjälä
Intel OTC

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