From a5741d057f2973dd1e4119ce6e5db02f54eeba55 Mon Sep 17 00:00:00 2001
From: Icenowy Zheng <uwu@icenowy.me>
Date: Thu, 18 Sep 2025 19:24:12 +0800
Subject: [PATCH] modesetting: properly use fb_id of front_bo for reverse PRIME
 CRTC

When doing reverse PRIME, the buffer being scaned out is still the front
BO.

Properly reuse its fb_id, to prevent adding a FB for the front_bo each
time the fb_id is requested.

Signed-off-by: Icenowy Zheng <uwu@icenowy.me>
Part-of: <https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/2064>
---
 hw/xfree86/drivers/modesetting/drmmode_display.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/hw/xfree86/drivers/modesetting/drmmode_display.c b/hw/xfree86/drivers/modesetting/drmmode_display.c
index ec0def926..c1f533c90 100644
--- a/hw/xfree86/drivers/modesetting/drmmode_display.c
+++ b/hw/xfree86/drivers/modesetting/drmmode_display.c
@@ -644,8 +644,10 @@ drmmode_crtc_get_fb_id(xf86CrtcPtr crtc, uint32_t *fb_id, int *x, int *y)
                 msGetPixmapPriv(drmmode, drmmode_crtc->prime_pixmap);
             *fb_id = ppriv->fb_id;
             *x = 0;
-        } else
+        } else {
+            *fb_id = drmmode->fb_id;
             *x = drmmode_crtc->prime_pixmap_x;
+        }
         *y = 0;
     }
     else if (trf->buf[trf->back_idx ^ 1].px) {