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--- doc:appunti:hardware:mini_pc_intel_pentium_j3710 [2026/02/22 18:49] – [Blanking the Virtual Terminal] niccolo
+++ doc:appunti:hardware:mini_pc_intel_pentium_j3710 [2026/02/24 19:12] (current) – [DPMS (Display Power Management Signaling)] niccolo
@@ Line 99: / Line 99: @@
 </code>
+==== DPMS (Display Power Management Signaling) ====
+DPMS (Display Power Management Signaling) is a VESA standard used to reduce monitor power consumption by controlling power states (On, Standby, Suspend, Off) generally based on user inactivity.
+It is possible to control the status of the display connected to the frame buffer writing some values to the pseudo file:
+<code>
+echo 4 > /sys/class/graphics/fb0/blank
+echo 0 > /sys/class/graphics/fb0/blank
+</code>
+| 0  | FB_BLANK_UNBLANK  | Screen ON (normal operation)  |
+| 1  | FB_BLANK_NORMAL  | Blank screen (no power saving)  |
+| 2  | FB_BLANK_VSYNC_SUSPEND  | Suspend vertical sync  |
+| 3  | FB_BLANK_HSYNC_SUSPEND  | Suspend horizontal sync  |
+| 4  | FB_BLANK_POWERDOWN  | Power down display (DPMS off)  |
+Writing the value 4 to the pseudodevice changes the **DPMS** property from **On=0** to **Off=3**. It is possibile to check all the **connectors properties** using **modetest** (provided by the **libdrm-tests** Debian package):
+<code>
+modetest -M i915 -c
+opened device `Intel Graphics` on driver `i915` (version 1.6.0 at 20201103)
+Connectors:
+id      encoder status          name            size (mm)       modes   encoders
+      94      connected       HDMI-A-1        0x0             5       94
+  modes:
+        index name refresh (Hz) hdisp hss hse htot vdisp vss vse vtot
+  #0 1024x768 60.00 1024 1048 1184 1344 768 771 777 806 65000 flags: nhsync, nvsync; type: driver
+  #1 800x600 60.32 800 840 968 1056 600 601 605 628 40000 flags: phsync, pvsync; type: driver
+  ...
+DPMS:
+        flags: enum
+        enums: On=0 Standby=1 Suspend=2 Off=3
+        value: 3
+    ....
+     106     connected       HDMI-A-2        470x260         30      106
+  modes:
+        index name refresh (Hz) hdisp hss hse htot vdisp vss vse vtot
+  #0 1024x600 59.82 1024 1068 1156 1344 600 603 609 625 50250 flags: phsync, nvsync; type: preferred, driver
+  #1 1920x1080 60.00 1920 2008 2052 2200 1080 1084 1089 1125 148500 flags: phsync, pvsync; type: driver
+  ...
+DPMS:
+        flags: enum
+        enums: On=0 Standby=1 Suspend=2 Off=3
+        value: 3
+    ....
+</code>
+FIXME What is this?
+<code>
+/usr/sbin/vbetool dpms on
+/usr/sbin/vbetool dpms off
+</code>
 ===== Pygame =====
-When running a Pygame app in **SDL_VIDEODRIVER=fbcon**, the SDL (Simple DirectMedia Layer library) takes over VT, so the **setterm** command does not work.
+We verified what driver uses the Pygame app:
+<code python>
+import pygame
+pygame.init()
+print(pygame.display.get_driver())
+</code>
+It says **KMSDRM**.
+Using that driver the SDL **Simple DirectMedia Layer** library owns the DRM master, external tools (modetest, sysfs) do not work for blanking the screen. The correct solution is to control this from inside SDL.
+===== HDMI Monitor supported modes =====
+<code>
+cat /sys/class/drm/card0-HDMI-A-1/modes
+</code>
+<code>
+x600
+x600
+x600
+x600
+x600
+x576
+...
+</code>
+<code>
+fbset -i -fb /dev/fb0
+mode "1024x600"
+    geometry 1024 600 1024 600 32
+    timings 0 0 0 0 0 0 0
+    rgba 8/16,8/8,8/0,0/0
+endmode
+Frame buffer device information:
+    Name        : i915drmfb
+    Address     : 0
+    Size        : 2457600
+    Type        : PACKED PIXELS
+    Visual      : TRUECOLOR
+    XPanStep    : 1
+    YPanStep    : 1
+    YWrapStep   : 0
+    LineLength  : 4096
+    Accelerator : No
+</code>