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2fa91d15 JN |
1 | ========================= |
2 | Kernel Mode Setting (KMS) | |
3 | ========================= | |
4 | ||
2fa91d15 JN |
5 | Drivers must initialize the mode setting core by calling |
6 | :c:func:`drm_mode_config_init()` on the DRM device. The function | |
7 | initializes the :c:type:`struct drm_device <drm_device>` | |
8 | mode_config field and never fails. Once done, mode configuration must | |
9 | be 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 | ||
949619f3 DV |
18 | Modeset 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 | ||
311b62d9 DV |
27 | KMS Data Structures |
28 | =================== | |
2fa91d15 | 29 | |
311b62d9 | 30 | .. kernel-doc:: include/drm/drm_crtc.h |
2fa91d15 JN |
31 | :internal: |
32 | ||
311b62d9 DV |
33 | KMS API Functions |
34 | ================= | |
35 | ||
36 | .. kernel-doc:: drivers/gpu/drm/drm_crtc.c | |
2fa91d15 JN |
37 | :export: |
38 | ||
39 | Atomic Mode Setting Function Reference | |
311b62d9 | 40 | ====================================== |
2fa91d15 JN |
41 | |
42 | .. kernel-doc:: drivers/gpu/drm/drm_atomic.c | |
43 | :export: | |
44 | ||
5d070be6 | 45 | .. kernel-doc:: include/drm/drm_atomic.h |
2fa91d15 JN |
46 | :internal: |
47 | ||
48 | Frame Buffer Abstraction | |
311b62d9 | 49 | ======================== |
2fa91d15 | 50 | |
750fb8c4 DV |
51 | .. kernel-doc:: drivers/gpu/drm/drm_framebuffer.c |
52 | :doc: overview | |
2fa91d15 | 53 | |
7520a277 DV |
54 | Frame 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 | ||
2fa91d15 | 63 | DRM Format Handling |
311b62d9 | 64 | =================== |
2fa91d15 | 65 | |
84770cc2 LP |
66 | .. kernel-doc:: include/drm/drm_fourcc.h |
67 | :internal: | |
68 | ||
2fa91d15 JN |
69 | .. kernel-doc:: drivers/gpu/drm/drm_fourcc.c |
70 | :export: | |
71 | ||
72 | Dumb Buffer Objects | |
311b62d9 | 73 | =================== |
2fa91d15 JN |
74 | |
75 | The KMS API doesn't standardize backing storage object creation and | |
76 | leaves it to driver-specific ioctls. Furthermore actually creating a | |
77 | buffer object even for GEM-based drivers is done through a | |
78 | driver-specific ioctl - GEM only has a common userspace interface for | |
79 | sharing and destroying objects. While not an issue for full-fledged | |
80 | graphics stacks that include device-specific userspace components (in | |
81 | libdrm for instance), this limit makes DRM-based early boot graphics | |
82 | unnecessarily complex. | |
83 | ||
84 | Dumb objects partly alleviate the problem by providing a standard API to | |
85 | create dumb buffers suitable for scanout, which can then be used to | |
86 | create KMS frame buffers. | |
87 | ||
88 | To support dumb objects drivers must implement the dumb_create, | |
89 | dumb_destroy and dumb_map_offset operations. | |
90 | ||
91 | - int (\*dumb_create)(struct drm_file \*file_priv, struct | |
92 | drm_device \*dev, struct drm_mode_create_dumb \*args); | |
93 | The dumb_create operation creates a driver object (GEM or TTM | |
94 | handle) suitable for scanout based on the width, height and depth | |
95 | from the struct :c:type:`struct drm_mode_create_dumb | |
96 | <drm_mode_create_dumb>` argument. It fills the argument's | |
97 | handle, pitch and size fields with a handle for the newly created | |
98 | object and its line pitch and size in bytes. | |
99 | ||
100 | - int (\*dumb_destroy)(struct drm_file \*file_priv, struct | |
101 | drm_device \*dev, uint32_t handle); | |
102 | The dumb_destroy operation destroys a dumb object created by | |
103 | dumb_create. | |
104 | ||
105 | - int (\*dumb_map_offset)(struct drm_file \*file_priv, struct | |
106 | drm_device \*dev, uint32_t handle, uint64_t \*offset); | |
107 | The dumb_map_offset operation associates an mmap fake offset with | |
108 | the object given by the handle and returns it. Drivers must use the | |
109 | :c:func:`drm_gem_create_mmap_offset()` function to associate | |
110 | the fake offset as described in ?. | |
111 | ||
112 | Note that dumb objects may not be used for gpu acceleration, as has been | |
113 | attempted on some ARM embedded platforms. Such drivers really must have | |
114 | a hardware-specific ioctl to allocate suitable buffer objects. | |
115 | ||
43968d7b DV |
116 | Plane Abstraction |
117 | ================= | |
118 | ||
532b3671 DV |
119 | .. kernel-doc:: drivers/gpu/drm/drm_plane.c |
120 | :doc: overview | |
121 | ||
43968d7b DV |
122 | Plane Functions Reference |
123 | ------------------------- | |
124 | ||
125 | .. kernel-doc:: include/drm/drm_plane.h | |
126 | :internal: | |
127 | ||
128 | .. kernel-doc:: drivers/gpu/drm/drm_plane.c | |
129 | :export: | |
130 | ||
311b62d9 DV |
131 | Display Modes Function Reference |
132 | ================================ | |
2fa91d15 | 133 | |
311b62d9 DV |
134 | .. kernel-doc:: include/drm/drm_modes.h |
135 | :internal: | |
136 | ||
137 | .. kernel-doc:: drivers/gpu/drm/drm_modes.c | |
138 | :export: | |
2fa91d15 | 139 | |
ae2a6da8 DV |
140 | Connector Abstraction |
141 | ===================== | |
142 | ||
143 | .. kernel-doc:: drivers/gpu/drm/drm_connector.c | |
144 | :doc: overview | |
145 | ||
146 | Connector Functions Reference | |
147 | ----------------------------- | |
52217195 DV |
148 | |
149 | .. kernel-doc:: include/drm/drm_connector.h | |
150 | :internal: | |
151 | ||
152 | .. kernel-doc:: drivers/gpu/drm/drm_connector.c | |
153 | :export: | |
154 | ||
321a95ae DV |
155 | Encoder Abstraction |
156 | =================== | |
157 | ||
e03e6de0 DV |
158 | .. kernel-doc:: drivers/gpu/drm/drm_encoder.c |
159 | :doc: overview | |
160 | ||
161 | Encoder Functions Reference | |
162 | --------------------------- | |
163 | ||
321a95ae DV |
164 | .. kernel-doc:: include/drm/drm_encoder.h |
165 | :internal: | |
166 | ||
167 | .. kernel-doc:: drivers/gpu/drm/drm_encoder.c | |
168 | :export: | |
169 | ||
2fa91d15 JN |
170 | KMS Initialization and Cleanup |
171 | ============================== | |
172 | ||
173 | A KMS device is abstracted and exposed as a set of planes, CRTCs, | |
174 | encoders and connectors. KMS drivers must thus create and initialize all | |
175 | those objects at load time after initializing mode setting. | |
176 | ||
177 | CRTCs (:c:type:`struct drm_crtc <drm_crtc>`) | |
178 | -------------------------------------------- | |
179 | ||
180 | A CRTC is an abstraction representing a part of the chip that contains a | |
181 | pointer to a scanout buffer. Therefore, the number of CRTCs available | |
182 | determines how many independent scanout buffers can be active at any | |
183 | given time. The CRTC structure contains several fields to support this: | |
184 | a pointer to some video memory (abstracted as a frame buffer object), a | |
185 | display mode, and an (x, y) offset into the video memory to support | |
186 | panning or configurations where one piece of video memory spans multiple | |
187 | CRTCs. | |
188 | ||
189 | CRTC Initialization | |
190 | ~~~~~~~~~~~~~~~~~~~ | |
191 | ||
192 | A KMS device must create and register at least one struct | |
193 | :c:type:`struct drm_crtc <drm_crtc>` instance. The instance is | |
194 | allocated and zeroed by the driver, possibly as part of a larger | |
195 | structure, and registered with a call to :c:func:`drm_crtc_init()` | |
196 | with a pointer to CRTC functions. | |
197 | ||
2fa91d15 | 198 | |
2fa91d15 JN |
199 | Cleanup |
200 | ------- | |
201 | ||
202 | The DRM core manages its objects' lifetime. When an object is not needed | |
203 | anymore the core calls its destroy function, which must clean up and | |
204 | free every resource allocated for the object. Every | |
205 | :c:func:`drm_\*_init()` call must be matched with a corresponding | |
206 | :c:func:`drm_\*_cleanup()` call to cleanup CRTCs | |
207 | (:c:func:`drm_crtc_cleanup()`), planes | |
208 | (:c:func:`drm_plane_cleanup()`), encoders | |
209 | (:c:func:`drm_encoder_cleanup()`) and connectors | |
210 | (:c:func:`drm_connector_cleanup()`). Furthermore, connectors that | |
211 | have been added to sysfs must be removed by a call to | |
212 | :c:func:`drm_connector_unregister()` before calling | |
213 | :c:func:`drm_connector_cleanup()`. | |
214 | ||
215 | Connectors state change detection must be cleanup up with a call to | |
216 | :c:func:`drm_kms_helper_poll_fini()`. | |
217 | ||
218 | Output discovery and initialization example | |
219 | ------------------------------------------- | |
220 | ||
221 | :: | |
222 | ||
223 | void intel_crt_init(struct drm_device *dev) | |
224 | { | |
225 | struct drm_connector *connector; | |
226 | struct intel_output *intel_output; | |
227 | ||
228 | intel_output = kzalloc(sizeof(struct intel_output), GFP_KERNEL); | |
229 | if (!intel_output) | |
230 | return; | |
231 | ||
232 | connector = &intel_output->base; | |
233 | drm_connector_init(dev, &intel_output->base, | |
234 | &intel_crt_connector_funcs, DRM_MODE_CONNECTOR_VGA); | |
235 | ||
236 | drm_encoder_init(dev, &intel_output->enc, &intel_crt_enc_funcs, | |
237 | DRM_MODE_ENCODER_DAC); | |
238 | ||
239 | drm_mode_connector_attach_encoder(&intel_output->base, | |
240 | &intel_output->enc); | |
241 | ||
242 | /* Set up the DDC bus. */ | |
243 | intel_output->ddc_bus = intel_i2c_create(dev, GPIOA, "CRTDDC_A"); | |
244 | if (!intel_output->ddc_bus) { | |
245 | dev_printk(KERN_ERR, &dev->pdev->dev, "DDC bus registration " | |
246 | "failed.\n"); | |
247 | return; | |
248 | } | |
249 | ||
250 | intel_output->type = INTEL_OUTPUT_ANALOG; | |
251 | connector->interlace_allowed = 0; | |
252 | connector->doublescan_allowed = 0; | |
253 | ||
254 | drm_encoder_helper_add(&intel_output->enc, &intel_crt_helper_funcs); | |
255 | drm_connector_helper_add(connector, &intel_crt_connector_helper_funcs); | |
256 | ||
257 | drm_connector_register(connector); | |
258 | } | |
259 | ||
260 | In the example above (taken from the i915 driver), a CRTC, connector and | |
261 | encoder combination is created. A device-specific i2c bus is also | |
262 | created for fetching EDID data and performing monitor detection. Once | |
263 | the process is complete, the new connector is registered with sysfs to | |
264 | make its properties available to applications. | |
265 | ||
2fa91d15 | 266 | KMS Locking |
311b62d9 | 267 | =========== |
2fa91d15 JN |
268 | |
269 | .. kernel-doc:: drivers/gpu/drm/drm_modeset_lock.c | |
270 | :doc: kms locking | |
271 | ||
272 | .. kernel-doc:: include/drm/drm_modeset_lock.h | |
273 | :internal: | |
274 | ||
275 | .. kernel-doc:: drivers/gpu/drm/drm_modeset_lock.c | |
276 | :export: | |
277 | ||
278 | KMS Properties | |
279 | ============== | |
280 | ||
59e71ee7 DV |
281 | Property Types and Blob Property Support |
282 | ---------------------------------------- | |
283 | ||
c8458c7e DV |
284 | .. kernel-doc:: drivers/gpu/drm/drm_property.c |
285 | :doc: overview | |
286 | ||
59e71ee7 DV |
287 | .. kernel-doc:: include/drm/drm_property.h |
288 | :internal: | |
289 | ||
290 | .. kernel-doc:: drivers/gpu/drm/drm_property.c | |
291 | :export: | |
292 | ||
1e4d84c6 DV |
293 | Plane Composition Properties |
294 | ---------------------------- | |
295 | ||
296 | .. kernel-doc:: drivers/gpu/drm/drm_blend.c | |
297 | :doc: overview | |
52a9fcda DV |
298 | |
299 | .. kernel-doc:: drivers/gpu/drm/drm_blend.c | |
300 | :export: | |
301 | ||
a6acccf8 DV |
302 | Color Management Properties |
303 | --------------------------- | |
304 | ||
305 | .. kernel-doc:: drivers/gpu/drm/drm_color_mgmt.c | |
306 | :doc: overview | |
307 | ||
308 | .. kernel-doc:: include/drm/drm_color_mgmt.h | |
309 | :internal: | |
310 | ||
311 | .. kernel-doc:: drivers/gpu/drm/drm_color_mgmt.c | |
312 | :export: | |
313 | ||
2fa91d15 JN |
314 | Existing KMS Properties |
315 | ----------------------- | |
316 | ||
317 | The following table gives description of drm properties exposed by | |
318 | various modules/drivers. | |
319 | ||
320 | .. csv-table:: | |
321 | :header-rows: 1 | |
322 | :file: kms-properties.csv | |
323 | ||
324 | Vertical Blanking | |
325 | ================= | |
326 | ||
327 | Vertical blanking plays a major role in graphics rendering. To achieve | |
328 | tear-free display, users must synchronize page flips and/or rendering to | |
329 | vertical blanking. The DRM API offers ioctls to perform page flips | |
330 | synchronized to vertical blanking and wait for vertical blanking. | |
331 | ||
332 | The DRM core handles most of the vertical blanking management logic, | |
333 | which involves filtering out spurious interrupts, keeping race-free | |
334 | blanking counters, coping with counter wrap-around and resets and | |
335 | keeping use counts. It relies on the driver to generate vertical | |
336 | blanking interrupts and optionally provide a hardware vertical blanking | |
337 | counter. Drivers must implement the following operations. | |
338 | ||
339 | - int (\*enable_vblank) (struct drm_device \*dev, int crtc); void | |
340 | (\*disable_vblank) (struct drm_device \*dev, int crtc); | |
341 | Enable or disable vertical blanking interrupts for the given CRTC. | |
342 | ||
343 | - u32 (\*get_vblank_counter) (struct drm_device \*dev, int crtc); | |
344 | Retrieve the value of the vertical blanking counter for the given | |
345 | CRTC. If the hardware maintains a vertical blanking counter its value | |
346 | should be returned. Otherwise drivers can use the | |
347 | :c:func:`drm_vblank_count()` helper function to handle this | |
348 | operation. | |
349 | ||
350 | Drivers must initialize the vertical blanking handling core with a call | |
351 | to :c:func:`drm_vblank_init()` in their load operation. | |
352 | ||
353 | Vertical blanking interrupts can be enabled by the DRM core or by | |
354 | drivers themselves (for instance to handle page flipping operations). | |
355 | The DRM core maintains a vertical blanking use count to ensure that the | |
356 | interrupts are not disabled while a user still needs them. To increment | |
357 | the use count, drivers call :c:func:`drm_vblank_get()`. Upon | |
358 | return vertical blanking interrupts are guaranteed to be enabled. | |
359 | ||
360 | To decrement the use count drivers call | |
361 | :c:func:`drm_vblank_put()`. Only when the use count drops to zero | |
362 | will the DRM core disable the vertical blanking interrupts after a delay | |
363 | by scheduling a timer. The delay is accessible through the | |
364 | vblankoffdelay module parameter or the ``drm_vblank_offdelay`` global | |
365 | variable and expressed in milliseconds. Its default value is 5000 ms. | |
366 | Zero means never disable, and a negative value means disable | |
367 | immediately. Drivers may override the behaviour by setting the | |
368 | :c:type:`struct drm_device <drm_device>` | |
369 | vblank_disable_immediate flag, which when set causes vblank interrupts | |
370 | to be disabled immediately regardless of the drm_vblank_offdelay | |
371 | value. The flag should only be set if there's a properly working | |
372 | hardware vblank counter present. | |
373 | ||
374 | When a vertical blanking interrupt occurs drivers only need to call the | |
375 | :c:func:`drm_handle_vblank()` function to account for the | |
376 | interrupt. | |
377 | ||
378 | Resources allocated by :c:func:`drm_vblank_init()` must be freed | |
379 | with a call to :c:func:`drm_vblank_cleanup()` in the driver unload | |
380 | operation handler. | |
381 | ||
382 | Vertical Blanking and Interrupt Handling Functions Reference | |
383 | ------------------------------------------------------------ | |
384 | ||
385 | .. kernel-doc:: drivers/gpu/drm/drm_irq.c | |
386 | :export: | |
387 | ||
34a67dd7 DV |
388 | .. kernel-doc:: include/drm/drm_irq.h |
389 | :internal: |