glx: create DRI screen for display GPU incase of prime

The created DRI screen can be used to allocate VRAM memory from
display GPU in case of prime.

v2: add comments to make code readable (Pierre-Eric)
    remove driver name match check
v3: keep old path for non-mesa driver (Michel Dänzer)
v4: fallback if driver not found for display GPU (Michel Dänzer)
    fallback if create screen fail for display gpu (Michel Dänzer)

Signed-off-by: Yogesh Mohanmarimuthu <yogesh.mohanmarimuthu@amd.com>
Acked-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/10595>

src/glx/dri3_glx.c

@@ -395,6 +395,7 @@ dri3_create_drawable(struct glx_screen *base, XID xDrawable,
       return NULL;
    }
 
+   pdraw->loader_drawable.dri_screen_display_gpu = psc->driScreenDisplayGPU;
    return &pdraw->base;
 }
 
@@ -607,8 +608,13 @@ dri3_destroy_screen(struct glx_screen *base)
    struct dri3_screen *psc = (struct dri3_screen *) base;
 
    /* Free the direct rendering per screen data */
-   if (psc->is_different_gpu)
+   if (psc->is_different_gpu) {
+      if (psc->driScreenDisplayGPU) {
+         loader_dri3_close_screen(psc->driScreenDisplayGPU);
+         (*psc->core->destroyScreen) (psc->driScreenDisplayGPU);
+      }
       close(psc->fd_display_gpu);
+   }
    loader_dri3_close_screen(psc->driScreen);
    (*psc->core->destroyScreen) (psc->driScreen);
    driDestroyConfigs(psc->driver_configs);
@@ -836,7 +842,7 @@ dri3_create_screen(int screen, struct glx_display * priv)
    struct dri3_screen *psc;
    __GLXDRIscreen *psp;
    struct glx_config *configs = NULL, *visuals = NULL;
-   char *driverName, *tmp;
+   char *driverName, *driverNameDisplayGPU, *tmp;
    int i;
 
    psc = calloc(1, sizeof *psc);
@@ -900,6 +906,27 @@ dri3_create_screen(int screen, struct glx_display * priv)
       goto handle_error;
    }
 
+   if (psc->is_different_gpu) {
+      driverNameDisplayGPU = loader_get_driver_for_fd(psc->fd_display_gpu);
+      if (driverNameDisplayGPU) {
+
+         /* check if driver name is matching so that non mesa drivers
+          * will not crash. Also need this check since image extension
+          * pointer from render gpu is shared with display gpu. Image
+          * extension pointer is shared because it keeps things simple.
+          */
+         if (strcmp(driverName, driverNameDisplayGPU) == 0) {
+            psc->driScreenDisplayGPU =
+               psc->image_driver->createNewScreen2(screen, psc->fd_display_gpu,
+                                                   pdp->loader_extensions,
+                                                   extensions,
+                                                   &driver_configs, psc);
+         }
+
+         free(driverNameDisplayGPU);
+      }
+   }
+
    psc->driScreen =
       psc->image_driver->createNewScreen2(screen, psc->fd,
                                           pdp->loader_extensions,
@@ -1019,6 +1046,9 @@ handle_error:
    if (psc->driScreen)
        psc->core->destroyScreen(psc->driScreen);
    psc->driScreen = NULL;
+   if (psc->driScreenDisplayGPU)
+       psc->core->destroyScreen(psc->driScreenDisplayGPU);
+   psc->driScreenDisplayGPU = NULL;
    if (psc->fd >= 0)
       close(psc->fd);
    if (psc->fd_display_gpu >= 0)

src/glx/dri3_priv.h

@@ -89,6 +89,12 @@ struct dri3_screen {
    __DRIscreen *driScreen;
    __GLXDRIscreen vtable;
 
+   /* DRI screen is created for display GPU in case of prime.
+    * This screen is used to allocate linear_buffer from
+    * display GPU space in dri3_alloc_render_buffer() function.
+    */
+   __DRIscreen *driScreenDisplayGPU;
+
    const __DRIimageExtension *image;
    const __DRIimageDriverExtension *image_driver;
    const __DRIcoreExtension *core;

src/loader/loader_dri3_helper.h

@@ -128,6 +128,9 @@ struct loader_dri3_drawable {
    bool is_different_gpu;
    bool multiplanes_available;
 
+   /* DRI screen created for display GPU in case of prime */
+   __DRIscreen *dri_screen_display_gpu;
+
    /* Present extension capabilities
     */
    uint32_t present_capabilities;