https://gitlab.freedesktop.org/xorg/xserver/-/commit/35af1299e73483eaf93d913a960e1d1738bc7de6

From: Povilas Kanapickas <povilas@radix.lt>
Date: Sat, 13 Nov 2021 17:23:54 +0200
Subject: [PATCH] Revert "hw/xfree86: Propagate physical dimensions from DRM
 connector"

Quite a lot of applications currently expect the screen DPI exposed by
the X server to be 96 even when the real display DPI is different.
Additionally, currently Xwayland completely ignores any hardware
information and sets the DPI to 96. Accordingly the new behavior, even
if it fixes a bug, should not be enabled automatically to all users.

A better solution would be to make the default DPI stay as is and enable
the correct behavior with a command line option (maybe -dpi auto, or
similar). For now let's just revert the bug fix.

This reverts commit 05b3c681ea2f478c0cb941c2f8279919cf78de6d.

Signed-off-by: Povilas Kanapickas <povilas@radix.lt>
--- a/hw/xfree86/common/xf86Helper.c
+++ b/hw/xfree86/common/xf86Helper.c
@@ -55,7 +55,6 @@
 #include "xf86Xinput.h"
 #include "xf86InPriv.h"
 #include "mivalidate.h"
-#include "xf86Crtc.h"
 
 /* For xf86GetClocks */
 #if defined(CSRG_BASED) || defined(__GNU__)
@@ -852,9 +851,8 @@ xf86SetDpi(ScrnInfoPtr pScrn, int x, int y)
 {
     MessageType from = X_DEFAULT;
     xf86MonPtr DDC = (xf86MonPtr) (pScrn->monitor->DDC);
-    int probedWidthmm, probedHeightmm;
+    int ddcWidthmm, ddcHeightmm;
     int widthErr, heightErr;
-    xf86OutputPtr compat = xf86CompatOutput(pScrn);
 
     /* XXX Maybe there is no need for widthmm/heightmm in ScrnInfoRec */
     pScrn->widthmm = pScrn->monitor->widthmm;
@@ -864,15 +862,11 @@ xf86SetDpi(ScrnInfoPtr pScrn, int x, int y)
         /* DDC gives display size in mm for individual modes,
          * but cm for monitor
          */
-        probedWidthmm = DDC->features.hsize * 10;  /* 10mm in 1cm */
-        probedHeightmm = DDC->features.vsize * 10; /* 10mm in 1cm */
-    }
-    else if (compat && compat->mm_width > 0 && compat->mm_height > 0) {
-        probedWidthmm = compat->mm_width;
-        probedHeightmm = compat->mm_height;
+        ddcWidthmm = DDC->features.hsize * 10;  /* 10mm in 1cm */
+        ddcHeightmm = DDC->features.vsize * 10; /* 10mm in 1cm */
     }
     else {
-        probedWidthmm = probedHeightmm = 0;
+        ddcWidthmm = ddcHeightmm = 0;
     }
 
     if (monitorResolution > 0) {
@@ -898,15 +892,15 @@ xf86SetDpi(ScrnInfoPtr pScrn, int x, int y)
                    pScrn->widthmm, pScrn->heightmm);
 
         /* Warn if config and probe disagree about display size */
-        if (probedWidthmm && probedHeightmm) {
+        if (ddcWidthmm && ddcHeightmm) {
             if (pScrn->widthmm > 0) {
-                widthErr = abs(probedWidthmm - pScrn->widthmm);
+                widthErr = abs(ddcWidthmm - pScrn->widthmm);
             }
             else {
                 widthErr = 0;
             }
             if (pScrn->heightmm > 0) {
-                heightErr = abs(probedHeightmm - pScrn->heightmm);
+                heightErr = abs(ddcHeightmm - pScrn->heightmm);
             }
             else {
                 heightErr = 0;
@@ -915,17 +909,17 @@ xf86SetDpi(ScrnInfoPtr pScrn, int x, int y)
                 /* Should include config file name for monitor here */
                 xf86DrvMsg(pScrn->scrnIndex, X_WARNING,
                            "Probed monitor is %dx%d mm, using Displaysize %dx%d mm\n",
-                           probedWidthmm, probedHeightmm, pScrn->widthmm,
+                           ddcWidthmm, ddcHeightmm, pScrn->widthmm,
                            pScrn->heightmm);
             }
         }
     }
-    else if (probedWidthmm && probedHeightmm) {
+    else if (ddcWidthmm && ddcHeightmm) {
         from = X_PROBED;
         xf86DrvMsg(pScrn->scrnIndex, from, "Display dimensions: (%d, %d) mm\n",
-                   probedWidthmm, probedHeightmm);
-        pScrn->widthmm = probedWidthmm;
-        pScrn->heightmm = probedHeightmm;
+                   ddcWidthmm, ddcHeightmm);
+        pScrn->widthmm = ddcWidthmm;
+        pScrn->heightmm = ddcHeightmm;
         if (pScrn->widthmm > 0) {
             pScrn->xDpi =
                 (int) ((double) pScrn->virtualX * MMPERINCH / pScrn->widthmm);
--- a/hw/xfree86/modes/xf86Crtc.c
+++ b/hw/xfree86/modes/xf86Crtc.c
@@ -3256,10 +3256,8 @@ xf86OutputSetEDID(xf86OutputPtr output, xf86MonPtr edid_mon)
     free(output->MonInfo);
 
     output->MonInfo = edid_mon;
-    if (edid_mon) {
-        output->mm_width = 0;
-        output->mm_height = 0;
-    }
+    output->mm_width = 0;
+    output->mm_height = 0;
 
     if (debug_modes) {
         xf86DrvMsg(scrn->scrnIndex, X_INFO, "EDID for output %s\n",
--- a/hw/xfree86/modes/xf86RandR12.c
+++ b/hw/xfree86/modes/xf86RandR12.c
@@ -806,12 +806,6 @@ xf86RandR12CreateScreenResources(ScreenPtr pScreen)
                 mmWidth = output->conf_monitor->mon_width;
                 mmHeight = output->conf_monitor->mon_height;
             }
-            else if (output &&
-                (output->mm_width > 0 &&
-                 output->mm_height > 0)) {
-                mmWidth = output->mm_width;
-                mmHeight = output->mm_height;
-            }
             else {
                 /*
                  * Otherwise, just set the screen to DEFAULT_DPI
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