From a330e82f6e78be71b5df581fb85ccc03fe134a8a Mon Sep 17 00:00:00 2001
From: stefan11111 <stefan11111github@gmail.com>
Date: Sat, 23 May 2026 00:06:04 +0300
Subject: [PATCH] kdrive/fbdev: Implement `-noaccel` flag

Similar to `-dumb`, but allows disabling acceleration
for a single screen, as oposed to the whole server

Signed-off-by: stefan11111 <stefan11111github@gmail.com>
---
 hw/kdrive/fbdev/Xfbdev.man  |  3 +++
 hw/kdrive/fbdev/fb_glamor.c | 18 ++++++++++++++++++
 hw/kdrive/fbdev/fbdev.h     |  2 +-
 hw/kdrive/fbdev/fbinit.c    |  9 +++++++++
 4 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/hw/kdrive/fbdev/Xfbdev.man b/hw/kdrive/fbdev/Xfbdev.man
index f058ad7397..245dec11d6 100644
--- a/hw/kdrive/fbdev/Xfbdev.man
+++ b/hw/kdrive/fbdev/Xfbdev.man
@@ -45,6 +45,9 @@ tells the X server to enable master permissions on the dri fd it uses
 disables the ShadowFB layer on supported hw, may slightly increase performance.
 May also lead to flickering.
 .TP 8
+.B -noaccel
+disables hw acceleration (similar to -dumb, but only for a single screen).
+.TP 8
 .B -glamor
 force enables glamor render acceleration (even on top of sw renderers like softpipe/llvmpipe).
 .TP 8
diff --git a/hw/kdrive/fbdev/fb_glamor.c b/hw/kdrive/fbdev/fb_glamor.c
index c64c269d8e..55f9b7add4 100644
--- a/hw/kdrive/fbdev/fb_glamor.c
+++ b/hw/kdrive/fbdev/fb_glamor.c
@@ -32,6 +32,11 @@ fbdevInitAccel(ScreenPtr pScreen)
     FbdevScrPriv *scrpriv = screen->driver;
     FbScreenConf *config = screen->card->closure;
 
+    if (config->fbNoAccel) {
+        /* Only disable accel for this screen */
+        return TRUE;
+    }
+
     if (config->fbdev_dri_path) {
         scrpriv->dri_fd = open(config->fbdev_dri_path, O_RDWR);
         if (scrpriv->dri_fd >= 0) {
@@ -113,6 +118,10 @@ fbdevEnableAccel(ScreenPtr pScreen)
     FbdevScrPriv *scrpriv = screen->driver;
     FbScreenConf *config = screen->card->closure;
 
+    if (config->fbNoAccel) {
+        return;
+    }
+
     if (config->fbdev_drm_master && scrpriv->dri_fd >= 0) {
         drmSetMaster(scrpriv->dri_fd);
     }
@@ -128,6 +137,10 @@ fbdevDisableAccel(ScreenPtr pScreen)
     FbdevScrPriv *scrpriv = screen->driver;
     FbScreenConf *config = screen->card->closure;
 
+    if (config->fbNoAccel) {
+        return;
+    }
+
     if (config->fbdev_drm_master && scrpriv->dri_fd >= 0) {
         drmDropMaster(scrpriv->dri_fd);
     }
@@ -140,6 +153,11 @@ fbdevFiniAccel(ScreenPtr pScreen)
     KdScreenPriv(pScreen);
     KdScreenInfo *screen = pScreenPriv->screen;
     FbdevScrPriv *scrpriv = screen->driver;
+    FbScreenConf *config = screen->card->closure;
+
+    if (config->fbNoAccel) {
+        return;
+    }
 
     if (scrpriv->dri_fd >= 0) {
         close(scrpriv->dri_fd);
diff --git a/hw/kdrive/fbdev/fbdev.h b/hw/kdrive/fbdev/fbdev.h
index 8c92a0c6b2..c389f35fd9 100644
--- a/hw/kdrive/fbdev/fbdev.h
+++ b/hw/kdrive/fbdev/fbdev.h
@@ -55,7 +55,7 @@ typedef struct _fbdevScrPriv {
 typedef struct _fbScreenConf {
 const char *fbdevDevicePath;
 Bool fbDisableShadow;
-
+bool fbNoAccel;
 #ifdef GLAMOR
 char *fbdev_glvnd_provider;
 
diff --git a/hw/kdrive/fbdev/fbinit.c b/hw/kdrive/fbdev/fbinit.c
index 2d2a76797c..37e9a58538 100644
--- a/hw/kdrive/fbdev/fbinit.c
+++ b/hw/kdrive/fbdev/fbinit.c
@@ -96,6 +96,8 @@ fbdevLogScreenInfo(FbScreenConf *config, int screen_num)
                config->fbdevDevicePath ? config->fbdevDevicePath : "not passed");
     LogMessage(X_INFO, "Xfbdev(%d): ShadowFB %s\n", screen_num,
                config->fbDisableShadow ? "disabled" : "enabled");
+    LogMessage(X_INFO, "Xfbdev(%d): HW Acceleration %s\n", screen_num,
+               config->fbNoAccel ? "disabled" : "enabled");
 #ifdef GLAMOR
     LogMessage(X_INFO, "Xfbdev(%d): glvnd library: %s\n", screen_num,
                config->fbdev_glvnd_provider ? config->fbdev_glvnd_provider : "not passed");
@@ -167,6 +169,8 @@ ddxUseMsg(void)
         ("-drm-master          Enable master permissions on the fd used for dri\n");
     ErrorF
         ("-noshadow            Disable the ShadowFB layer if possible\n");
+    ErrorF
+        ("-noaccel             Disable hw acceleration (per screen)\n");
     ErrorF
         ("-glamor              Force enable glamor render acceleration if possible\n");
     ErrorF
@@ -215,6 +219,11 @@ ddxProcessArgument(int argc, char **argv, int i)
         return 1;
     }
 
+    if (!strcmp(argv[i], "-noaccel")) {
+        fbCurrScreen->fbNoAccel = TRUE;
+        return 1;
+    }
+
 #ifdef GLAMOR
     if (!strcmp(argv[i], "-glamor")) {
         fbCurrScreen->fbForceGlamor = TRUE;