[WIP] Implement DPMS get/setValue (Screen Off/On for KMS) #478

DisDis · 2025-05-01T19:47:55Z

I added kms drm property set function.
The code is dirty, but it works.
Any suggestions for improvement?

It allows turn off/on screen.

For my case I use HDMI-0.
kmsprint -p
show:

Connector 0 (33) HDMI-A-1 (connected)
    EDID (1) = blob-id 678 len 256 (immutable)
    DPMS (2) = 0 (On) [On=0|Standby=1|Suspend=2|Off=3]
    TILE (4) = blob-id 0 (immutable)
    link-status (5) = 0 (Good) [Good=0|Bad=1]

Screen ON:

if (kmsDrmService.isAvailable()) {
  // DPMS (2) = 3 (Off) [On=0|Standby=1|Suspend=2|Off=3]
  kmsDrmService.setProperty(2, 0);
}

Screen OFF:

if (kmsDrmService.isAvailable()) {
  // DPMS (2) = 0 (On) [On=0|Standby=1|Suspend=2|Off=3]
  kmsDrmService.setProperty(2, 3);
}

Service:
static final KmsDrmService kmsDrmService = KmsDrmService();

/*
uint32_t KMS_DRM_isAvailable();

void KMS_DRM_setProperty(uint32_t propId, uint64_t value) ;

uint64_t KMS_DRM_getProperty(uint32_t propId);
*/

typedef KMS_DRM_setPropertyFuncType = ffi.Void Function(ffi.Uint32 propId, ffi.Uint64 value);
typedef KMS_DRM_setPropertyType = void Function(int propId, int value);

typedef KMS_DRM_isAvailableFuncType = ffi.Uint32 Function();
typedef KMS_DRM_isAvailableType = int Function();

class KmsDrmService {
  final _KmsDrmService _service = _KmsDrmService.instance;
  bool isAvailable() {
    if (_service.KMS_DRM_isAvailable == null || _service.KMS_DRM_isAvailable!() == 0) {
      return false;
    }
    return true;
  }

  void setProperty(int propId, int value) {
    if (_service.KMS_DRM_setProperty == null) {
      return;
    }
    _service.KMS_DRM_setProperty!(propId, value);
  }
}

class _KmsDrmService {
  final KMS_DRM_setPropertyType? KMS_DRM_setProperty;
  final KMS_DRM_isAvailableType? KMS_DRM_isAvailable;
  _KmsDrmService._constructor({required this.KMS_DRM_setProperty, required this.KMS_DRM_isAvailable});

  factory _KmsDrmService._() {
    final lib = ffi.DynamicLibrary.process();

    try {
      final KMS_DRM_setPropertyLFunc = lib.lookupFunction<KMS_DRM_setPropertyFuncType, KMS_DRM_setPropertyType>("KMS_DRM_setProperty");
      final KMS_DRM_isAvailableLFunc = lib.lookupFunction<KMS_DRM_isAvailableFuncType, KMS_DRM_isAvailableType>("KMS_DRM_isAvailable");

      return _KmsDrmService._constructor(
        KMS_DRM_setProperty: KMS_DRM_setPropertyLFunc,
        KMS_DRM_isAvailable: KMS_DRM_isAvailableLFunc,
      );
    } on ArgumentError {
      return _KmsDrmService._constructor(
        KMS_DRM_setProperty: null,
        KMS_DRM_isAvailable: null,
      );
    }
  }

  static _KmsDrmService? _instance;

  static _KmsDrmService get instance {
    if (_instance == null) {
      _instance = _KmsDrmService._();
    }

    return _instance!;
  }
}

DisDis · 2025-05-01T19:49:08Z

I used this example https://github.com/tomba/kmsxx/blob/master/utils/kmsblank.cpp#L77

src/flutter-pi.c

ardera · 2025-05-02T13:36:53Z

Thanks for the contribution @DisDis !

I think providing support for DPMS & backlight is definitely useful, but a generic way to set KMS properties might be a bit too powerful. It's very easy to shoot yourself in the foot with that and it can easily conflict with flutter-pi's modesetting.

Might be better to provide an abstraction specifically for DPMS (and/or backlight). Just a package where you can do something like:

void main() async {
  final dpms = await DPMS.getInstance(); // optionally allow passing the view id here, for multi-view

  await dpms.setMode(PowerMode.on);
  await Future.delayed(Duration(seconds: 5));
  await dpms.setMode(PowerMode.standby);

  // ...
}

For backlight, one could implement a platform interface for: https://github.com/aaassseee/screen_brightness/

Weston has its own little sub-library to help with backlight: https://gitlab.freedesktop.org/wayland/weston/-/blob/main/libweston/backend-drm/libbacklight.c, that could just be added to the flutter-pi source tree under third_party/libbacklight.

src/modesetting.c

+
+#define DPMS_PROPERTY_NAME "DPMS"
+#define DPMS_ERROR_PROPERTY_ID 0
+// FIXME: Is 0 error value?


DisDis · 2025-05-03T07:30:33Z

Hi @ardera.
I implemented get/setDPMSValue.
When this MR merge, I will start implement DPMS package in "flutter_packages"

ardera · 2026-01-25T13:03:28Z

I have to apologize @DisDis , I just realized I reviewed this, but never submitted the review

ardera

some comments, and can you rebase on top of dev?
and move the logic into kms_req_builder and kms_window (window.c), maybe compositor

ardera · 2025-05-03T08:56:15Z

src/modesetting.c

+uint32_t kms_drm_getDPMSPropertyId(struct drmdev *drmdev, uint32_t connector_id){
+    ASSERT_NOT_NULL(drmdev);
+    ASSERT_NOT_NULL(drmdev->fd);
+    drmModeObjectProperties *props = drmModeObjectGetProperties(drmdev->fd, connector_id, DRM_MODE_OBJECT_CONNECTOR);
+    if (props == NULL){
+       int ok = errno;
+        LOG_ERROR("Could not get connector properties. drmModeObjectGetProperties: %s\n", strerror(ok));
+        return DPMS_ERROR_PROPERTY_ID;
+    }
+
+    uint32_t result_prop_id = DPMS_ERROR_PROPERTY_ID;
+	for (unsigned i = 0; i < props->count_props; ++i) {
+		uint32_t prop_id = props->props[i];
+        drmModePropertyRes *drm_prop = drmModeGetProperty(drmdev->fd, prop_id);
+        if (drm_prop != NULL) {
+            if (streq(drm_prop->name, DPMS_PROPERTY_NAME)){
+                result_prop_id = prop_id;
+            }
+        }
+        drmModeFreeProperty(drm_prop);
+	}
+
+	drmModeFreeObjectProperties(props);
+    return result_prop_id;
+}
+
+uint32_t kms_drm_getDPMSPropertyValue(struct drmdev *drmdev, uint32_t connector_id){
+    ASSERT_NOT_NULL(drmdev);
+    ASSERT_NOT_NULL(drmdev->fd);
+    drmModeObjectProperties *props = drmModeObjectGetProperties(drmdev->fd, connector_id, DRM_MODE_OBJECT_CONNECTOR);
+    if (props == NULL){
+       int ok = errno;
+        LOG_ERROR("Could not get connector properties. drmModeObjectGetProperties: %s\n", strerror(ok));
+        return DPMS_ERROR_PROPERTY_ID;
+    }
+
+    uint32_t result_prop_value = DPMS_ERROR_PROPERTY_VALUE;
+	for (unsigned i = 0; i < props->count_props; ++i) {
+		uint32_t prop_id = props->props[i];
+        drmModePropertyRes *drm_prop = drmModeGetProperty(drmdev->fd, prop_id);
+        if (drm_prop != NULL) {
+            if (streq(drm_prop->name, DPMS_PROPERTY_NAME)){
+                result_prop_value = props->prop_values[i];
+            }
+        }
+        drmModeFreeProperty(drm_prop);
+	}
+
+	drmModeFreeObjectProperties(props);
+    return result_prop_value;
+}
+
+
+uint64_t kms_dpms_getValue(struct drmdev *drmdev){
+    ASSERT_NOT_NULL(drmdev);
+
+    struct drm_connector *connectors =  drmdev->connectors;
+    size_t n_connectors = drmdev->n_connectors;
+    uint64_t result = DPMS_ERROR_PROPERTY_VALUE;
+
+    for (int i = 0; i < n_connectors; i++) {
+        if (
+        connectors->variable_state.connection_state == kConnected_DrmConnectionState ||
+        connectors->variable_state.connection_state == kUnknown_DrmConnectionState ){
+            uint32_t property_id = kms_drm_getDPMSPropertyId(drmdev, connectors->id);
+            if (property_id != DPMS_ERROR_PROPERTY_ID){
+                // Return only first value
+                result = kms_drm_getDPMSPropertyValue(drmdev, connectors->id);
+                break;
+            }
+        }
+    }
+
+    return result;
+}
+
+
+void kms_dpms_setValue(struct drmdev *drmdev, uint64_t value){
+    ASSERT_NOT_NULL(drmdev);
+
+    struct drm_connector *connectors =  drmdev->connectors;
+    size_t n_connectors = drmdev->n_connectors;
+
+    for (int i = 0; i < n_connectors; i++) {
+        if (
+        connectors->variable_state.connection_state == kConnected_DrmConnectionState ||
+        connectors->variable_state.connection_state == kUnknown_DrmConnectionState ){
+            uint32_t property_id = kms_drm_getDPMSPropertyId(drmdev, connectors->id);
+            if (property_id != DPMS_ERROR_PROPERTY_ID){
+                drmModeObjectSetProperty(drmdev->fd, connectors->id, DRM_MODE_OBJECT_CONNECTOR, property_id, value);
+            }
+        }
+    }
+}


mhh, this basically circumvents all the modesetting code that's already there in modesetting.c.

What you could do is create a new constructor for kms_req_builder that just turns a display off:

int kms_req_builder_new_dpms_off(struct drmdev *drmdev, uint32_t crtc_id) { /* ... */ }

And make all other kms reqs implicity turn DPMS on. (Because there's no reason to build a frame if the display is off)

And then the DPMS logic goes in the window.c, maybe compositor.c

ardera · 2025-05-03T09:02:35Z

src/modesetting.c

+#define DPMS_PROPERTY_NAME "DPMS"
+#define DPMS_ERROR_PROPERTY_ID 0
+// FIXME: Is 0 error value?
+#define DPMS_ERROR_PROPERTY_VALUE 0


This is already being parsed by the modesetting code, e.g. the DPMS string definition is at:

flutter-pi/src/modesetting.h

Line 42 in 6365c91

V("DPMS", dpms) \

The property id of the DPMS property for some given connector is contained in the struct drm_connector, e.g.:

uint32_t get_dpms_property_id(struct drmdev *drmdev, int connector_index) { return drmdev->connectors[connector_index].ids.dpms; }

ardera · 2026-01-25T13:06:39Z

src/modesetting.c

+        connectors->variable_state.connection_state == kUnknown_DrmConnectionState ){
+            uint32_t property_id = kms_drm_getDPMSPropertyId(drmdev, connectors->id);
+            if (property_id != DPMS_ERROR_PROPERTY_ID){
+                drmModeObjectSetProperty(drmdev->fd, connectors->id, DRM_MODE_OBJECT_CONNECTOR, property_id, value);


unfortunately that API is a bit "deceitful", it'll actually blockingly commit a frame, so it can wait up to 16ms

DisDis · 2026-01-31T16:10:22Z

some comments, and can you rebase on top of dev? and move the logic into kms_req_builder and kms_window (window.c), maybe compositor

I'll try to do it.

If a device doesn't support rotation, there's really nothing we can do. So just try to apply rotation, but don't fail if it doesn't work. adds enforce_rotation property to struct kms_fb_layer, and makes egl_gbm_render_surface, vk_gbm_render_surface, dmabuf_surface specify false.

ardera · 2026-01-31T16:58:37Z

I'll try to do it.

Thank you. 👍 I'm also here to assist if there's any problems

DisDis · 2026-01-31T17:02:37Z

@ardera
If I move it to window.c , how do I replace flutterpi->drmdev ?
For example:

uint64_t dpms_getProperty(){
    return kms_dpms_getValue(flutterpi->drmdev);
}

ardera · 2026-01-31T17:22:44Z

so the thing that communicates with the dart side I would put in the plugins dir, something like this maybe:
dpms_plugin.c:

// 0 => off, 1 => on, negative value => errno-style error
int flutterpi_dpms_get() {
  if (value == NULL) return -EINVAL;

  return compositor_get_dpms(flutterpi->compositor);
}

// 0 => success, non-zero value => errno-style error
int flutterpi_dpms_set(bool value) {
  return compositor_set_dpms(flutterpi->compositor, value);
}

void dpms_plugin_init(/*...*/) {
  // ...
}

DisDis · 2026-01-31T18:00:30Z

mhh, this basically circumvents all the modesetting code that's already there in modesetting.c.

What you could do is create a new constructor for kms_req_builder that just turns a display off:
int kms_req_builder_new_dpms_off(struct drmdev *drmdev, uint32_t crtc_id) {
  /* ... */
}
And make all other kms reqs implicity turn DPMS on. (Because there's no reason to build a frame if the display is off)

And then the DPMS logic goes in the window.c, maybe compositor.c

@ardera

I'm not get.
What needs to be done?

ardera · 2026-01-31T20:01:10Z

I'm not get. What needs to be done?

Roughly like this:

add a field in kms_req_builder:

struct kms_req_builder {
  // ...
  bool set_dpms_off;
}

create a new method drmdev_create_dpms_off_req() that works the same as drmdev_create_request_builder(), except you also set set_dpms_off to true. and make it return a kms_req instead of kms_req_builder, so you can't add layers to it.

in kms_req_commit_common: if set_dpms_off is set to true, do

drmModeAtomicAddProperty(
    /* ... */
    builder->connector->ids.dpms,
    builder->is_dpms_off ? DRM_MODE_DPMS_OFF : DRM_MODE_DPMS_ON
);

then, in window.c: add a kms_window_set_dpms virtual function

static int kms_window_set_dpms(struct window *window, bool dpms) {
  if (!dpms) {
    window->active = false;
    struct kms_req_builder *b = drmdev_create_request_builder_dpms_off( /*...*/ );
    struct kms_req *r = kms_req_builder_build(b);
    return kms_req_commit_blocking(r, NULL); 
  } else {
    window->active = true;
    // present the last frame
    if (window->composition != NULL) {
        kms_window_push_composition_locked(window, window->composition);
    }
  }
}

virtual here means it should be called via function pointer, like window_push_composition or window_get_render_surface-

in kms_window_push_composition_locked, check if active is set. if it is set, don't actually present the frame, but save it for later in window->composition.

and then call all that from compositor_set_dpms, and that in turn from the plugin code.

DisDis · 2026-01-31T21:14:22Z

@ardera I updated code.
But
'in kms_window_push_composition_locked, check if active is set. if it is set, don't actually present the frame, but save it for later in window->composition.'
I don't really understand what needs to be done here :(

I don't yet understand how we'll enable dpms. I created
"drmdev_create_dpms_on_req," but maybe that's unnecessary.

DisDis mentioned this pull request May 1, 2025

Turn off screen after certain time #465

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github-advanced-security bot found potential problems May 1, 2025

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github-advanced-security bot found potential problems May 3, 2025

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src/modesetting.c Outdated

#define DPMS_PROPERTY_NAME "DPMS"

#define DPMS_ERROR_PROPERTY_ID 0

// FIXME: Is 0 error value?

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FIXME comment

FIXME comment: Is 0 error value?

DisDis changed the title ~~[MVP/WIP] add support kms drm property set~~ [WIP] Implement DPMS get/setValue (Screen Off/On for KMS) May 3, 2025

DisDis mentioned this pull request May 3, 2025

add linux_dpms package ardera/flutter_packages#41

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ardera reviewed Jan 25, 2026

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DisDis and others added 4 commits January 31, 2026 19:17

add support kms drm property set

9002c4a

remove comment

19fc33a

implement DPMS get/set property

d876b58

remove kms_drm_getDPMSPropertyId

621138d

DisDis force-pushed the support_kms_drm_property_set branch from f8f45d5 to 621138d Compare January 31, 2026 17:23

DisDis changed the base branch from master to dev January 31, 2026 17:25

Igor Demyanov added 2 commits January 31, 2026 20:53

move dpms to compositor.c and dpms_plugin.c

e0057e0

dpms iterate over all connectors

1315846

fix compositor_set_dpms

1d11e9e

migrate to drmModeAtomicAddProperty

0e6e625

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[WIP] Implement DPMS get/setValue (Screen Off/On for KMS) #478

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