blob: 53b872c105d24f0741e06f463ab2fdadbb0c01cd [file] [log] [blame]
Jani Nikula2fa91d12016-06-21 14:49:02 +03001=========================
2Kernel Mode Setting (KMS)
3=========================
4
Jani Nikula2fa91d12016-06-21 14:49:02 +03005Drivers must initialize the mode setting core by calling
6:c:func:`drm_mode_config_init()` on the DRM device. The function
7initializes the :c:type:`struct drm_device <drm_device>`
8mode_config field and never fails. Once done, mode configuration must
9be setup by initializing the following fields.
10
11- int min_width, min_height; int max_width, max_height;
12 Minimum and maximum width and height of the frame buffers in pixel
13 units.
14
15- struct drm_mode_config_funcs \*funcs;
16 Mode setting functions.
17
Daniel Vetter949619f2016-08-29 10:27:51 +020018Modeset Base Object Abstraction
19===============================
20
21.. kernel-doc:: include/drm/drm_mode_object.h
22 :internal:
23
24.. kernel-doc:: drivers/gpu/drm/drm_mode_object.c
25 :export:
26
Daniel Vetter311b62d2016-08-12 22:48:41 +020027KMS Data Structures
28===================
Jani Nikula2fa91d12016-06-21 14:49:02 +030029
Daniel Vetter311b62d2016-08-12 22:48:41 +020030.. kernel-doc:: include/drm/drm_crtc.h
Jani Nikula2fa91d12016-06-21 14:49:02 +030031 :internal:
32
Daniel Vetter311b62d2016-08-12 22:48:41 +020033KMS API Functions
34=================
35
36.. kernel-doc:: drivers/gpu/drm/drm_crtc.c
Jani Nikula2fa91d12016-06-21 14:49:02 +030037 :export:
38
39Atomic Mode Setting Function Reference
Daniel Vetter311b62d2016-08-12 22:48:41 +020040======================================
Jani Nikula2fa91d12016-06-21 14:49:02 +030041
42.. kernel-doc:: drivers/gpu/drm/drm_atomic.c
43 :export:
44
Daniel Vetter5d070be2016-08-12 22:48:46 +020045.. kernel-doc:: include/drm/drm_atomic.h
Jani Nikula2fa91d12016-06-21 14:49:02 +030046 :internal:
47
48Frame Buffer Abstraction
Daniel Vetter311b62d2016-08-12 22:48:41 +020049========================
Jani Nikula2fa91d12016-06-21 14:49:02 +030050
Daniel Vetter750fb8c2016-08-12 22:48:48 +020051.. kernel-doc:: drivers/gpu/drm/drm_framebuffer.c
52 :doc: overview
Jani Nikula2fa91d12016-06-21 14:49:02 +030053
Daniel Vetter7520a272016-08-15 16:07:02 +020054Frame Buffer Functions Reference
55--------------------------------
56
57.. kernel-doc:: drivers/gpu/drm/drm_framebuffer.c
58 :export:
59
60.. kernel-doc:: include/drm/drm_framebuffer.h
61 :internal:
62
Jani Nikula2fa91d12016-06-21 14:49:02 +030063DRM Format Handling
Daniel Vetter311b62d2016-08-12 22:48:41 +020064===================
Jani Nikula2fa91d12016-06-21 14:49:02 +030065
Jani Nikula2fa91d12016-06-21 14:49:02 +030066.. kernel-doc:: drivers/gpu/drm/drm_fourcc.c
67 :export:
68
69Dumb Buffer Objects
Daniel Vetter311b62d2016-08-12 22:48:41 +020070===================
Jani Nikula2fa91d12016-06-21 14:49:02 +030071
72The KMS API doesn't standardize backing storage object creation and
73leaves it to driver-specific ioctls. Furthermore actually creating a
74buffer object even for GEM-based drivers is done through a
75driver-specific ioctl - GEM only has a common userspace interface for
76sharing and destroying objects. While not an issue for full-fledged
77graphics stacks that include device-specific userspace components (in
78libdrm for instance), this limit makes DRM-based early boot graphics
79unnecessarily complex.
80
81Dumb objects partly alleviate the problem by providing a standard API to
82create dumb buffers suitable for scanout, which can then be used to
83create KMS frame buffers.
84
85To support dumb objects drivers must implement the dumb_create,
86dumb_destroy and dumb_map_offset operations.
87
88- int (\*dumb_create)(struct drm_file \*file_priv, struct
89 drm_device \*dev, struct drm_mode_create_dumb \*args);
90 The dumb_create operation creates a driver object (GEM or TTM
91 handle) suitable for scanout based on the width, height and depth
92 from the struct :c:type:`struct drm_mode_create_dumb
93 <drm_mode_create_dumb>` argument. It fills the argument's
94 handle, pitch and size fields with a handle for the newly created
95 object and its line pitch and size in bytes.
96
97- int (\*dumb_destroy)(struct drm_file \*file_priv, struct
98 drm_device \*dev, uint32_t handle);
99 The dumb_destroy operation destroys a dumb object created by
100 dumb_create.
101
102- int (\*dumb_map_offset)(struct drm_file \*file_priv, struct
103 drm_device \*dev, uint32_t handle, uint64_t \*offset);
104 The dumb_map_offset operation associates an mmap fake offset with
105 the object given by the handle and returns it. Drivers must use the
106 :c:func:`drm_gem_create_mmap_offset()` function to associate
107 the fake offset as described in ?.
108
109Note that dumb objects may not be used for gpu acceleration, as has been
110attempted on some ARM embedded platforms. Such drivers really must have
111a hardware-specific ioctl to allocate suitable buffer objects.
112
Daniel Vetter43968d72016-09-21 10:59:24 +0200113Plane Abstraction
114=================
115
Daniel Vetter532b3672016-09-21 10:59:25 +0200116.. kernel-doc:: drivers/gpu/drm/drm_plane.c
117 :doc: overview
118
Daniel Vetter43968d72016-09-21 10:59:24 +0200119Plane Functions Reference
120-------------------------
121
122.. kernel-doc:: include/drm/drm_plane.h
123 :internal:
124
125.. kernel-doc:: drivers/gpu/drm/drm_plane.c
126 :export:
127
Daniel Vetter311b62d2016-08-12 22:48:41 +0200128Display Modes Function Reference
129================================
Jani Nikula2fa91d12016-06-21 14:49:02 +0300130
Daniel Vetter311b62d2016-08-12 22:48:41 +0200131.. kernel-doc:: include/drm/drm_modes.h
132 :internal:
133
134.. kernel-doc:: drivers/gpu/drm/drm_modes.c
135 :export:
Jani Nikula2fa91d12016-06-21 14:49:02 +0300136
Daniel Vetterae2a6da2016-08-12 22:48:53 +0200137Connector Abstraction
138=====================
139
140.. kernel-doc:: drivers/gpu/drm/drm_connector.c
141 :doc: overview
142
143Connector Functions Reference
144-----------------------------
Daniel Vetter52217192016-08-12 22:48:50 +0200145
146.. kernel-doc:: include/drm/drm_connector.h
147 :internal:
148
149.. kernel-doc:: drivers/gpu/drm/drm_connector.c
150 :export:
151
Daniel Vetter321a95a2016-08-29 10:27:49 +0200152Encoder Abstraction
153===================
154
Daniel Vettere03e6de2016-08-29 10:27:50 +0200155.. kernel-doc:: drivers/gpu/drm/drm_encoder.c
156 :doc: overview
157
158Encoder Functions Reference
159---------------------------
160
Daniel Vetter321a95a2016-08-29 10:27:49 +0200161.. kernel-doc:: include/drm/drm_encoder.h
162 :internal:
163
164.. kernel-doc:: drivers/gpu/drm/drm_encoder.c
165 :export:
166
Jani Nikula2fa91d12016-06-21 14:49:02 +0300167KMS Initialization and Cleanup
168==============================
169
170A KMS device is abstracted and exposed as a set of planes, CRTCs,
171encoders and connectors. KMS drivers must thus create and initialize all
172those objects at load time after initializing mode setting.
173
174CRTCs (:c:type:`struct drm_crtc <drm_crtc>`)
175--------------------------------------------
176
177A CRTC is an abstraction representing a part of the chip that contains a
178pointer to a scanout buffer. Therefore, the number of CRTCs available
179determines how many independent scanout buffers can be active at any
180given time. The CRTC structure contains several fields to support this:
181a pointer to some video memory (abstracted as a frame buffer object), a
182display mode, and an (x, y) offset into the video memory to support
183panning or configurations where one piece of video memory spans multiple
184CRTCs.
185
186CRTC Initialization
187~~~~~~~~~~~~~~~~~~~
188
189A KMS device must create and register at least one struct
190:c:type:`struct drm_crtc <drm_crtc>` instance. The instance is
191allocated and zeroed by the driver, possibly as part of a larger
192structure, and registered with a call to :c:func:`drm_crtc_init()`
193with a pointer to CRTC functions.
194
Jani Nikula2fa91d12016-06-21 14:49:02 +0300195
Jani Nikula2fa91d12016-06-21 14:49:02 +0300196Cleanup
197-------
198
199The DRM core manages its objects' lifetime. When an object is not needed
200anymore the core calls its destroy function, which must clean up and
201free every resource allocated for the object. Every
202:c:func:`drm_\*_init()` call must be matched with a corresponding
203:c:func:`drm_\*_cleanup()` call to cleanup CRTCs
204(:c:func:`drm_crtc_cleanup()`), planes
205(:c:func:`drm_plane_cleanup()`), encoders
206(:c:func:`drm_encoder_cleanup()`) and connectors
207(:c:func:`drm_connector_cleanup()`). Furthermore, connectors that
208have been added to sysfs must be removed by a call to
209:c:func:`drm_connector_unregister()` before calling
210:c:func:`drm_connector_cleanup()`.
211
212Connectors state change detection must be cleanup up with a call to
213:c:func:`drm_kms_helper_poll_fini()`.
214
215Output discovery and initialization example
216-------------------------------------------
217
218::
219
220 void intel_crt_init(struct drm_device *dev)
221 {
222 struct drm_connector *connector;
223 struct intel_output *intel_output;
224
225 intel_output = kzalloc(sizeof(struct intel_output), GFP_KERNEL);
226 if (!intel_output)
227 return;
228
229 connector = &intel_output->base;
230 drm_connector_init(dev, &intel_output->base,
231 &intel_crt_connector_funcs, DRM_MODE_CONNECTOR_VGA);
232
233 drm_encoder_init(dev, &intel_output->enc, &intel_crt_enc_funcs,
234 DRM_MODE_ENCODER_DAC);
235
236 drm_mode_connector_attach_encoder(&intel_output->base,
237 &intel_output->enc);
238
239 /* Set up the DDC bus. */
240 intel_output->ddc_bus = intel_i2c_create(dev, GPIOA, "CRTDDC_A");
241 if (!intel_output->ddc_bus) {
242 dev_printk(KERN_ERR, &dev->pdev->dev, "DDC bus registration "
243 "failed.\n");
244 return;
245 }
246
247 intel_output->type = INTEL_OUTPUT_ANALOG;
248 connector->interlace_allowed = 0;
249 connector->doublescan_allowed = 0;
250
251 drm_encoder_helper_add(&intel_output->enc, &intel_crt_helper_funcs);
252 drm_connector_helper_add(connector, &intel_crt_connector_helper_funcs);
253
254 drm_connector_register(connector);
255 }
256
257In the example above (taken from the i915 driver), a CRTC, connector and
258encoder combination is created. A device-specific i2c bus is also
259created for fetching EDID data and performing monitor detection. Once
260the process is complete, the new connector is registered with sysfs to
261make its properties available to applications.
262
Jani Nikula2fa91d12016-06-21 14:49:02 +0300263KMS Locking
Daniel Vetter311b62d2016-08-12 22:48:41 +0200264===========
Jani Nikula2fa91d12016-06-21 14:49:02 +0300265
266.. kernel-doc:: drivers/gpu/drm/drm_modeset_lock.c
267 :doc: kms locking
268
269.. kernel-doc:: include/drm/drm_modeset_lock.h
270 :internal:
271
272.. kernel-doc:: drivers/gpu/drm/drm_modeset_lock.c
273 :export:
274
275KMS Properties
276==============
277
Daniel Vetter59e71ee2016-08-29 10:27:55 +0200278Property Types and Blob Property Support
279----------------------------------------
280
Daniel Vetterc8458c72016-08-29 10:27:57 +0200281.. kernel-doc:: drivers/gpu/drm/drm_property.c
282 :doc: overview
283
Daniel Vetter59e71ee2016-08-29 10:27:55 +0200284.. kernel-doc:: include/drm/drm_property.h
285 :internal:
286
287.. kernel-doc:: drivers/gpu/drm/drm_property.c
288 :export:
289
Daniel Vetter1e4d84c2016-09-21 10:59:27 +0200290Plane Composition Properties
291----------------------------
292
293.. kernel-doc:: drivers/gpu/drm/drm_blend.c
294 :doc: overview
Daniel Vetter52a9fcd2016-08-12 22:48:51 +0200295
296.. kernel-doc:: drivers/gpu/drm/drm_blend.c
297 :export:
298
Daniel Vettera6acccf2016-09-21 10:59:29 +0200299Color Management Properties
300---------------------------
301
302.. kernel-doc:: drivers/gpu/drm/drm_color_mgmt.c
303 :doc: overview
304
305.. kernel-doc:: include/drm/drm_color_mgmt.h
306 :internal:
307
308.. kernel-doc:: drivers/gpu/drm/drm_color_mgmt.c
309 :export:
310
Jani Nikula2fa91d12016-06-21 14:49:02 +0300311Existing KMS Properties
312-----------------------
313
314The following table gives description of drm properties exposed by
315various modules/drivers.
316
317.. csv-table::
318 :header-rows: 1
319 :file: kms-properties.csv
320
321Vertical Blanking
322=================
323
324Vertical blanking plays a major role in graphics rendering. To achieve
325tear-free display, users must synchronize page flips and/or rendering to
326vertical blanking. The DRM API offers ioctls to perform page flips
327synchronized to vertical blanking and wait for vertical blanking.
328
329The DRM core handles most of the vertical blanking management logic,
330which involves filtering out spurious interrupts, keeping race-free
331blanking counters, coping with counter wrap-around and resets and
332keeping use counts. It relies on the driver to generate vertical
333blanking interrupts and optionally provide a hardware vertical blanking
334counter. Drivers must implement the following operations.
335
336- int (\*enable_vblank) (struct drm_device \*dev, int crtc); void
337 (\*disable_vblank) (struct drm_device \*dev, int crtc);
338 Enable or disable vertical blanking interrupts for the given CRTC.
339
340- u32 (\*get_vblank_counter) (struct drm_device \*dev, int crtc);
341 Retrieve the value of the vertical blanking counter for the given
342 CRTC. If the hardware maintains a vertical blanking counter its value
343 should be returned. Otherwise drivers can use the
344 :c:func:`drm_vblank_count()` helper function to handle this
345 operation.
346
347Drivers must initialize the vertical blanking handling core with a call
348to :c:func:`drm_vblank_init()` in their load operation.
349
350Vertical blanking interrupts can be enabled by the DRM core or by
351drivers themselves (for instance to handle page flipping operations).
352The DRM core maintains a vertical blanking use count to ensure that the
353interrupts are not disabled while a user still needs them. To increment
354the use count, drivers call :c:func:`drm_vblank_get()`. Upon
355return vertical blanking interrupts are guaranteed to be enabled.
356
357To decrement the use count drivers call
358:c:func:`drm_vblank_put()`. Only when the use count drops to zero
359will the DRM core disable the vertical blanking interrupts after a delay
360by scheduling a timer. The delay is accessible through the
361vblankoffdelay module parameter or the ``drm_vblank_offdelay`` global
362variable and expressed in milliseconds. Its default value is 5000 ms.
363Zero means never disable, and a negative value means disable
364immediately. Drivers may override the behaviour by setting the
365:c:type:`struct drm_device <drm_device>`
366vblank_disable_immediate flag, which when set causes vblank interrupts
367to be disabled immediately regardless of the drm_vblank_offdelay
368value. The flag should only be set if there's a properly working
369hardware vblank counter present.
370
371When a vertical blanking interrupt occurs drivers only need to call the
372:c:func:`drm_handle_vblank()` function to account for the
373interrupt.
374
375Resources allocated by :c:func:`drm_vblank_init()` must be freed
376with a call to :c:func:`drm_vblank_cleanup()` in the driver unload
377operation handler.
378
379Vertical Blanking and Interrupt Handling Functions Reference
380------------------------------------------------------------
381
382.. kernel-doc:: drivers/gpu/drm/drm_irq.c
383 :export:
384
Daniel Vetter34a67dd2016-07-15 21:48:01 +0200385.. kernel-doc:: include/drm/drm_irq.h
386 :internal: