1 =============
2 DRM Internals
3 =============
4
5 This chapter documents DRM internals relevant
6 developers working to add support for the late
7 drivers.
8
9 First, we go over some typical driver initiali
10 setting up command buffers, creating an initia
11 and initializing core services. Subsequent sec
12 in more detail, providing implementation notes
13
14 The DRM layer provides several services to gra
15 them driven by the application interfaces it p
16 the library that wraps most of the DRM ioctls.
17 event handling, memory management, output mana
18 management, command submission & fencing, susp
19 DMA services.
20
21 Driver Initialization
22 =====================
23
24 At the core of every DRM driver is a :c:type:`
25 <drm_driver>` structure. Drivers typically sta
26 a drm_driver structure, and then pass it to
27 drm_dev_alloc() to allocate a device instance.
28 device instance is fully initialized it can be
29 it accessible from userspace) using drm_dev_re
30
31 The :c:type:`struct drm_driver <drm_driver>` s
32 contains static information that describes the
33 supports, and pointers to methods that the DRM
34 implement the DRM API. We will first go throug
35 drm_driver <drm_driver>` static information fi
36 then describe individual operations in details
37 sections.
38
39 Driver Information
40 ------------------
41
42 Major, Minor and Patchlevel
43 ~~~~~~~~~~~~~~~~~~~~~~~~~~~
44
45 int major; int minor; int patchlevel;
46 The DRM core identifies driver versions by a m
47 level triplet. The information is printed to t
48 initialization time and passed to userspace th
49 DRM_IOCTL_VERSION ioctl.
50
51 The major and minor numbers are also used to v
52 API version passed to DRM_IOCTL_SET_VERSION. W
53 changes between minor versions, applications c
54 DRM_IOCTL_SET_VERSION to select a specific ver
55 requested major isn't equal to the driver majo
56 is larger than the driver minor, the DRM_IOCTL
57 return an error. Otherwise the driver's set_ve
58 called with the requested version.
59
60 Name and Description
61 ~~~~~~~~~~~~~~~~~~~~
62
63 char \*name; char \*desc; char \*date;
64 The driver name is printed to the kernel log a
65 used for IRQ registration and passed to usersp
66 DRM_IOCTL_VERSION.
67
68 The driver description is a purely informative
69 userspace through the DRM_IOCTL_VERSION ioctl
70 the kernel.
71
72 Module Initialization
73 ---------------------
74
75 .. kernel-doc:: include/drm/drm_module.h
76 :doc: overview
77
78 Managing Ownership of the Framebuffer Aperture
79 ----------------------------------------------
80
81 .. kernel-doc:: drivers/gpu/drm/drm_aperture.c
82 :doc: overview
83
84 .. kernel-doc:: include/drm/drm_aperture.h
85 :internal:
86
87 .. kernel-doc:: drivers/gpu/drm/drm_aperture.c
88 :export:
89
90 Device Instance and Driver Handling
91 -----------------------------------
92
93 .. kernel-doc:: drivers/gpu/drm/drm_drv.c
94 :doc: driver instance overview
95
96 .. kernel-doc:: include/drm/drm_device.h
97 :internal:
98
99 .. kernel-doc:: include/drm/drm_drv.h
100 :internal:
101
102 .. kernel-doc:: drivers/gpu/drm/drm_drv.c
103 :export:
104
105 Driver Load
106 -----------
107
108 Component Helper Usage
109 ~~~~~~~~~~~~~~~~~~~~~~
110
111 .. kernel-doc:: drivers/gpu/drm/drm_drv.c
112 :doc: component helper usage recommendation
113
114 Memory Manager Initialization
115 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
116
117 Every DRM driver requires a memory manager whi
118 load time. DRM currently contains two memory m
119 Table Manager (TTM) and the Graphics Execution
120 document describes the use of the GEM memory m
121 details.
122
123 Miscellaneous Device Configuration
124 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
125
126 Another task that may be necessary for PCI dev
127 is mapping the video BIOS. On many devices, th
128 configuration, LCD panel timings (if any), and
129 device state. Mapping the BIOS can be done usi
130 call, a convenience function that takes care o
131 whether it has been shadowed into memory (typi
132 or exists on the PCI device in the ROM BAR. No
133 been mapped and any necessary information has
134 be unmapped; on many devices, the ROM address
135 other BARs, so leaving it mapped could cause u
136 hangs or memory corruption.
137
138 Managed Resources
139 -----------------
140
141 .. kernel-doc:: drivers/gpu/drm/drm_managed.c
142 :doc: managed resources
143
144 .. kernel-doc:: drivers/gpu/drm/drm_managed.c
145 :export:
146
147 .. kernel-doc:: include/drm/drm_managed.h
148 :internal:
149
150 Open/Close, File Operations and IOCTLs
151 ======================================
152
153 .. _drm_driver_fops:
154
155 File Operations
156 ---------------
157
158 .. kernel-doc:: drivers/gpu/drm/drm_file.c
159 :doc: file operations
160
161 .. kernel-doc:: include/drm/drm_file.h
162 :internal:
163
164 .. kernel-doc:: drivers/gpu/drm/drm_file.c
165 :export:
166
167 Misc Utilities
168 ==============
169
170 Printer
171 -------
172
173 .. kernel-doc:: include/drm/drm_print.h
174 :doc: print
175
176 .. kernel-doc:: include/drm/drm_print.h
177 :internal:
178
179 .. kernel-doc:: drivers/gpu/drm/drm_print.c
180 :export:
181
182 Utilities
183 ---------
184
185 .. kernel-doc:: include/drm/drm_util.h
186 :doc: drm utils
187
188 .. kernel-doc:: include/drm/drm_util.h
189 :internal:
190
191
192 Unit testing
193 ============
194
195 KUnit
196 -----
197
198 KUnit (Kernel unit testing framework) provides
199 within the Linux kernel.
200
201 This section covers the specifics for the DRM
202 about KUnit, please refer to Documentation/dev
203
204 How to run the tests?
205 ~~~~~~~~~~~~~~~~~~~~~
206
207 In order to facilitate running the test suite,
208 in ``drivers/gpu/drm/tests/.kunitconfig``. It
209 follows:
210
211 .. code-block:: bash
212
213 $ ./tools/testing/kunit/kunit.py run -
214 --kconfig_add CONFIG_VIRTIO_UM
215 --kconfig_add CONFIG_UML_PCI_O
216
217 .. note::
218 The configuration included in ``.kunit
219 possible.
220 ``CONFIG_VIRTIO_UML`` and ``CONFIG_UML
221 included in it because they are only r
222
223
224 Legacy Support Code
225 ===================
226
227 The section very briefly covers some of the ol
228 which is only used by old DRM drivers which ha
229 shadow-attach to the underlying device instead
230 driver. This also includes some of the old gen
231 command submission code. Do not use any of thi
232 drivers.
233
234 Legacy Suspend/Resume
235 ---------------------
236
237 The DRM core provides some suspend/resume code
238 suspend/resume support should provide save() a
239 These are called at suspend, hibernate, or res
240 perform any state save or restore required by
241 or hibernate states.
242
243 int (\*suspend) (struct drm_device \*, pm_mess
244 (\*resume) (struct drm_device \*);
245 Those are legacy suspend and resume methods wh
246 legacy shadow-attach driver registration funct
247 use the power management interface provided by
248 through the :c:type:`struct device_driver <dev
249 dev_pm_ops) and set these methods to NULL.
250
251 Legacy DMA Services
252 -------------------
253
254 This should cover how DMA mapping etc. is supp
255 functions are deprecated and should not be use
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