Re: [PATCH v2 2/6] ui/sdl2: Implement dpy dmabuf functions

[Akihiko Odaki <akihiko.odaki@daynix.com>]

On 2024/10/15 13:32, Dmitry Osipenko wrote:
> From: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
> 
> If EGL is used, we can rely on dmabuf to import textures without
> doing copies.
> 
> To get this working on X11, we use the existing SDL hint:
> SDL_HINT_VIDEO_X11_FORCE_EGL (because dmabuf can't be used with GLX).
> 
> Signed-off-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
> ---
>   include/ui/sdl2.h |  7 ++++++
>   ui/sdl2-gl.c      | 63 +++++++++++++++++++++++++++++++++++++++++++++++
>   ui/sdl2.c         | 31 +++++++++++++++++++++++
>   3 files changed, 101 insertions(+)
> 
> diff --git a/include/ui/sdl2.h b/include/ui/sdl2.h
> index dbe6e3d9739b..9daf5ecffae7 100644
> --- a/include/ui/sdl2.h
> +++ b/include/ui/sdl2.h
> @@ -45,6 +45,7 @@ struct sdl2_console {
>       bool gui_keysym;
>       SDL_GLContext winctx;
>       QKbdState *kbd;
> +    bool has_dmabuf;
>   #ifdef CONFIG_OPENGL
>       QemuGLShader *gls;
>       egl_fb guest_fb;
> @@ -96,5 +97,11 @@ void sdl2_gl_scanout_texture(DisplayChangeListener *dcl,
>                                void *d3d_tex2d);
>   void sdl2_gl_scanout_flush(DisplayChangeListener *dcl,
>                              uint32_t x, uint32_t y, uint32_t w, uint32_t h);
> +void sdl2_gl_scanout_dmabuf(DisplayChangeListener *dcl,
> +                            QemuDmaBuf *dmabuf);
> +void sdl2_gl_release_dmabuf(DisplayChangeListener *dcl,
> +                            QemuDmaBuf *dmabuf);
> +bool sdl2_gl_has_dmabuf(DisplayChangeListener *dcl);
> +void sdl2_gl_console_init(struct sdl2_console *scon);
>   
>   #endif /* SDL2_H */
> diff --git a/ui/sdl2-gl.c b/ui/sdl2-gl.c
> index b1fe96d6af22..7612af18292c 100644
> --- a/ui/sdl2-gl.c
> +++ b/ui/sdl2-gl.c
> @@ -26,6 +26,8 @@
>    */
>   
>   #include "qemu/osdep.h"
> +#include "qemu/main-loop.h"
> +#include "qemu/error-report.h"
>   #include "ui/console.h"
>   #include "ui/input.h"
>   #include "ui/sdl2.h"
> @@ -249,3 +251,64 @@ void sdl2_gl_scanout_flush(DisplayChangeListener *dcl,
>   
>       SDL_GL_SwapWindow(scon->real_window);
>   }
> +
> +void sdl2_gl_scanout_dmabuf(DisplayChangeListener *dcl,
> +                            QemuDmaBuf *dmabuf)
> +{
> +    struct sdl2_console *scon = container_of(dcl, struct sdl2_console, dcl);
> +
> +    assert(scon->opengl);
> +    SDL_GL_MakeCurrent(scon->real_window, scon->winctx);
> +
> +    egl_dmabuf_import_texture(dmabuf);
> +    if (!qemu_dmabuf_get_texture(dmabuf)) {
> +        error_report("%s: failed fd=%d", __func__, qemu_dmabuf_get_fd(dmabuf));
> +    }
> +
> +    sdl2_gl_scanout_texture(dcl, qemu_dmabuf_get_texture(dmabuf), false,
> +                            qemu_dmabuf_get_width(dmabuf),
> +                            qemu_dmabuf_get_height(dmabuf),
> +                            0, 0,
> +                            qemu_dmabuf_get_width(dmabuf),
> +                            qemu_dmabuf_get_height(dmabuf),
> +                            NULL);
> +
> +    if (qemu_dmabuf_get_allow_fences(dmabuf)) {
> +        scon->guest_fb.dmabuf = dmabuf;
> +    }
> +}
> +
> +void sdl2_gl_release_dmabuf(DisplayChangeListener *dcl,
> +                            QemuDmaBuf *dmabuf)
> +{
> +    egl_dmabuf_release_texture(dmabuf);
> +}
> +
> +bool sdl2_gl_has_dmabuf(DisplayChangeListener *dcl)
> +{
> +    struct sdl2_console *scon = container_of(dcl, struct sdl2_console, dcl);
> +
> +    return scon->has_dmabuf;
> +}
> +
> +void sdl2_gl_console_init(struct sdl2_console *scon)
> +{
> +    bool hidden = scon->hidden;
> +
> +    scon->hidden = true;
> +    scon->surface = qemu_create_displaysurface(1, 1);
> +    sdl2_window_create(scon);
> +
> +    /*
> +     * QEMU checks whether console supports dma-buf before switching
> +     * to the console.  To break this chicken-egg problem we pre-check
> +     * dma-buf availability beforehand using a dummy SDL window.
> +     */
> +    scon->has_dmabuf = qemu_egl_has_dmabuf();
> +
> +    sdl2_window_destroy(scon);
> +    qemu_free_displaysurface(scon->surface);
> +
> +    scon->surface = NULL;
> +    scon->hidden = hidden;
> +}
> diff --git a/ui/sdl2.c b/ui/sdl2.c
> index bd4f5a9da14a..607181071b84 100644
> --- a/ui/sdl2.c
> +++ b/ui/sdl2.c
> @@ -120,6 +120,9 @@ void sdl2_window_create(struct sdl2_console *scon)
>           /* The SDL renderer is only used by sdl2-2D, when OpenGL is disabled */
>           scon->real_renderer = SDL_CreateRenderer(scon->real_window, -1, 0);
>       }
> +
> +    qemu_egl_display = eglGetCurrentDisplay();
> +
>       sdl_update_caption(scon);
>   }
>   
> @@ -820,6 +823,10 @@ static const DisplayChangeListenerOps dcl_gl_ops = {
>       .dpy_gl_scanout_disable  = sdl2_gl_scanout_disable,
>       .dpy_gl_scanout_texture  = sdl2_gl_scanout_texture,
>       .dpy_gl_update           = sdl2_gl_scanout_flush,
> +
> +    .dpy_gl_scanout_dmabuf   = sdl2_gl_scanout_dmabuf,
> +    .dpy_gl_release_dmabuf   = sdl2_gl_release_dmabuf,
> +    .dpy_has_dmabuf          = sdl2_gl_has_dmabuf,
>   };
>   
>   static bool
> @@ -847,6 +854,28 @@ static void sdl2_display_early_init(DisplayOptions *o)
>       }
>   }
>   
> +static void sdl2_set_hint_x11_force_egl(void)
> +{
> +#if defined(SDL_HINT_VIDEO_X11_FORCE_EGL) && defined(EGL_KHR_platform_x11)

EGL_KHR_platform_x11 is always defined when CONFIG_OPENGL is defined.
Check CONFIG_OPENGL for the availability of EGL APIs.

> +    Display *x_disp = XOpenDisplay(NULL);

The availability of Xlib must be checked.

> +    EGLDisplay egl_display;
> +
> +    if (!x_disp) {
> +        return;
> +    }
> +
> +    /* Prefer EGL over GLX to get dma-buf support. */
> +    egl_display = eglGetDisplay((EGLNativeDisplayType)x_disp);
 > +> +    if (egl_display != EGL_NO_DISPLAY) {
> +        SDL_SetHint(SDL_HINT_VIDEO_X11_FORCE_EGL, "1");

SDL may not be going to use X11 but may use e.g., Wayland.

> +        eglTerminate(egl_display);
> +    }
> +
> +    XCloseDisplay(x_disp);
> +#endif
> +}
> +
>   static void sdl2_display_init(DisplayState *ds, DisplayOptions *o)
>   {
>       uint8_t data = 0;
> @@ -877,6 +906,7 @@ static void sdl2_display_init(DisplayState *ds, DisplayOptions *o)
>       SDL_SetHint(SDL_HINT_ALLOW_ALT_TAB_WHILE_GRABBED, "0");
>   #endif
>       SDL_SetHint(SDL_HINT_WINDOWS_NO_CLOSE_ON_ALT_F4, "1");
> +    sdl2_set_hint_x11_force_egl();
>       SDL_EnableScreenSaver();
>       memset(&info, 0, sizeof(info));
>       SDL_VERSION(&info.version);
> @@ -923,6 +953,7 @@ static void sdl2_display_init(DisplayState *ds, DisplayOptions *o)
>           sdl2_console[i].kbd = qkbd_state_init(con);
>           if (display_opengl) {
>               qemu_console_set_display_gl_ctx(con, &sdl2_console[i].dgc);
> +            sdl2_gl_console_init(&sdl2_console[i]);
>           }
>           register_displaychangelistener(&sdl2_console[i].dcl);
>