Commit | Line | Data |
---|---|---|
22554020 | 1 | ============= |
ca00c2b9 JN |
2 | DRM Internals |
3 | ============= | |
4 | ||
5 | This chapter documents DRM internals relevant to driver authors and | |
6 | developers working to add support for the latest features to existing | |
7 | drivers. | |
8 | ||
9 | First, we go over some typical driver initialization requirements, like | |
10 | setting up command buffers, creating an initial output configuration, | |
11 | and initializing core services. Subsequent sections cover core internals | |
12 | in more detail, providing implementation notes and examples. | |
13 | ||
14 | The DRM layer provides several services to graphics drivers, many of | |
15 | them driven by the application interfaces it provides through libdrm, | |
16 | the library that wraps most of the DRM ioctls. These include vblank | |
17 | event handling, memory management, output management, framebuffer | |
18 | management, command submission & fencing, suspend/resume support, and | |
19 | DMA services. | |
20 | ||
21 | Driver Initialization | |
22554020 | 22 | ===================== |
ca00c2b9 JN |
23 | |
24 | At the core of every DRM driver is a :c:type:`struct drm_driver | |
25 | <drm_driver>` structure. Drivers typically statically initialize | |
26 | a drm_driver structure, and then pass it to | |
27 | :c:func:`drm_dev_alloc()` to allocate a device instance. After the | |
28 | device instance is fully initialized it can be registered (which makes | |
29 | it accessible from userspace) using :c:func:`drm_dev_register()`. | |
30 | ||
31 | The :c:type:`struct drm_driver <drm_driver>` structure | |
32 | contains static information that describes the driver and features it | |
33 | supports, and pointers to methods that the DRM core will call to | |
34 | implement the DRM API. We will first go through the :c:type:`struct | |
35 | drm_driver <drm_driver>` static information fields, and will | |
36 | then describe individual operations in details as they get used in later | |
37 | sections. | |
38 | ||
39 | Driver Information | |
22554020 | 40 | ------------------ |
ca00c2b9 JN |
41 | |
42 | Driver Features | |
2fa91d15 | 43 | ~~~~~~~~~~~~~~~ |
ca00c2b9 JN |
44 | |
45 | Drivers inform the DRM core about their requirements and supported | |
46 | features by setting appropriate flags in the driver_features field. | |
47 | Since those flags influence the DRM core behaviour since registration | |
48 | time, most of them must be set to registering the :c:type:`struct | |
49 | drm_driver <drm_driver>` instance. | |
50 | ||
51 | u32 driver_features; | |
52 | ||
53 | DRIVER_USE_AGP | |
54 | Driver uses AGP interface, the DRM core will manage AGP resources. | |
55 | ||
3cbf6a5d DV |
56 | DRIVER_LEGACY |
57 | Denote a legacy driver using shadow attach. Don't use. | |
58 | ||
59 | DRIVER_KMS_LEGACY_CONTEXT | |
60 | Used only by nouveau for backwards compatibility with existing userspace. | |
61 | Don't use. | |
ca00c2b9 JN |
62 | |
63 | DRIVER_PCI_DMA | |
64 | Driver is capable of PCI DMA, mapping of PCI DMA buffers to | |
65 | userspace will be enabled. Deprecated. | |
66 | ||
67 | DRIVER_SG | |
68 | Driver can perform scatter/gather DMA, allocation and mapping of | |
69 | scatter/gather buffers will be enabled. Deprecated. | |
70 | ||
71 | DRIVER_HAVE_DMA | |
72 | Driver supports DMA, the userspace DMA API will be supported. | |
73 | Deprecated. | |
74 | ||
75 | DRIVER_HAVE_IRQ; DRIVER_IRQ_SHARED | |
76 | DRIVER_HAVE_IRQ indicates whether the driver has an IRQ handler | |
77 | managed by the DRM Core. The core will support simple IRQ handler | |
78 | installation when the flag is set. The installation process is | |
79 | described in ?. | |
80 | ||
81 | DRIVER_IRQ_SHARED indicates whether the device & handler support | |
82 | shared IRQs (note that this is required of PCI drivers). | |
83 | ||
84 | DRIVER_GEM | |
85 | Driver use the GEM memory manager. | |
86 | ||
87 | DRIVER_MODESET | |
88 | Driver supports mode setting interfaces (KMS). | |
89 | ||
90 | DRIVER_PRIME | |
91 | Driver implements DRM PRIME buffer sharing. | |
92 | ||
93 | DRIVER_RENDER | |
94 | Driver supports dedicated render nodes. | |
95 | ||
96 | DRIVER_ATOMIC | |
97 | Driver supports atomic properties. In this case the driver must | |
98 | implement appropriate obj->atomic_get_property() vfuncs for any | |
99 | modeset objects with driver specific properties. | |
100 | ||
e9083420 DA |
101 | DRIVER_SYNCOBJ |
102 | Driver support drm sync objects. | |
103 | ||
ca00c2b9 | 104 | Major, Minor and Patchlevel |
2fa91d15 | 105 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
ca00c2b9 JN |
106 | |
107 | int major; int minor; int patchlevel; | |
108 | The DRM core identifies driver versions by a major, minor and patch | |
109 | level triplet. The information is printed to the kernel log at | |
110 | initialization time and passed to userspace through the | |
111 | DRM_IOCTL_VERSION ioctl. | |
112 | ||
113 | The major and minor numbers are also used to verify the requested driver | |
114 | API version passed to DRM_IOCTL_SET_VERSION. When the driver API | |
115 | changes between minor versions, applications can call | |
116 | DRM_IOCTL_SET_VERSION to select a specific version of the API. If the | |
117 | requested major isn't equal to the driver major, or the requested minor | |
118 | is larger than the driver minor, the DRM_IOCTL_SET_VERSION call will | |
119 | return an error. Otherwise the driver's set_version() method will be | |
120 | called with the requested version. | |
121 | ||
122 | Name, Description and Date | |
2fa91d15 | 123 | ~~~~~~~~~~~~~~~~~~~~~~~~~~ |
ca00c2b9 JN |
124 | |
125 | char \*name; char \*desc; char \*date; | |
126 | The driver name is printed to the kernel log at initialization time, | |
127 | used for IRQ registration and passed to userspace through | |
128 | DRM_IOCTL_VERSION. | |
129 | ||
130 | The driver description is a purely informative string passed to | |
131 | userspace through the DRM_IOCTL_VERSION ioctl and otherwise unused by | |
132 | the kernel. | |
133 | ||
134 | The driver date, formatted as YYYYMMDD, is meant to identify the date of | |
135 | the latest modification to the driver. However, as most drivers fail to | |
136 | update it, its value is mostly useless. The DRM core prints it to the | |
137 | kernel log at initialization time and passes it to userspace through the | |
138 | DRM_IOCTL_VERSION ioctl. | |
139 | ||
140 | Device Instance and Driver Handling | |
22554020 | 141 | ----------------------------------- |
ca00c2b9 JN |
142 | |
143 | .. kernel-doc:: drivers/gpu/drm/drm_drv.c | |
144 | :doc: driver instance overview | |
145 | ||
6c4789ed DV |
146 | .. kernel-doc:: include/drm/drm_drv.h |
147 | :internal: | |
148 | ||
1ea35768 DV |
149 | .. kernel-doc:: drivers/gpu/drm/drm_drv.c |
150 | :export: | |
151 | ||
ca00c2b9 | 152 | Driver Load |
22554020 | 153 | ----------- |
ca00c2b9 | 154 | |
ca00c2b9 | 155 | |
3ed4351a DV |
156 | IRQ Helper Library |
157 | ~~~~~~~~~~~~~~~~~~ | |
158 | ||
159 | .. kernel-doc:: drivers/gpu/drm/drm_irq.c | |
160 | :doc: irq helpers | |
161 | ||
162 | .. kernel-doc:: drivers/gpu/drm/drm_irq.c | |
163 | :export: | |
164 | ||
ca00c2b9 | 165 | Memory Manager Initialization |
2fa91d15 | 166 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
ca00c2b9 JN |
167 | |
168 | Every DRM driver requires a memory manager which must be initialized at | |
169 | load time. DRM currently contains two memory managers, the Translation | |
170 | Table Manager (TTM) and the Graphics Execution Manager (GEM). This | |
171 | document describes the use of the GEM memory manager only. See ? for | |
172 | details. | |
173 | ||
174 | Miscellaneous Device Configuration | |
2fa91d15 | 175 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
ca00c2b9 JN |
176 | |
177 | Another task that may be necessary for PCI devices during configuration | |
178 | is mapping the video BIOS. On many devices, the VBIOS describes device | |
179 | configuration, LCD panel timings (if any), and contains flags indicating | |
180 | device state. Mapping the BIOS can be done using the pci_map_rom() | |
181 | call, a convenience function that takes care of mapping the actual ROM, | |
182 | whether it has been shadowed into memory (typically at address 0xc0000) | |
183 | or exists on the PCI device in the ROM BAR. Note that after the ROM has | |
184 | been mapped and any necessary information has been extracted, it should | |
185 | be unmapped; on many devices, the ROM address decoder is shared with | |
186 | other BARs, so leaving it mapped could cause undesired behaviour like | |
187 | hangs or memory corruption. | |
188 | ||
189 | Bus-specific Device Registration and PCI Support | |
22554020 | 190 | ------------------------------------------------ |
ca00c2b9 JN |
191 | |
192 | A number of functions are provided to help with device registration. The | |
193 | functions deal with PCI and platform devices respectively and are only | |
194 | provided for historical reasons. These are all deprecated and shouldn't | |
195 | be used in new drivers. Besides that there's a few helpers for pci | |
196 | drivers. | |
197 | ||
198 | .. kernel-doc:: drivers/gpu/drm/drm_pci.c | |
199 | :export: | |
200 | ||
ca00c2b9 | 201 | Open/Close, File Operations and IOCTLs |
22554020 | 202 | ====================================== |
ca00c2b9 | 203 | |
bb2eaba6 DV |
204 | .. _drm_driver_fops: |
205 | ||
ca00c2b9 | 206 | File Operations |
22554020 | 207 | --------------- |
ca00c2b9 | 208 | |
9acdac68 | 209 | .. kernel-doc:: drivers/gpu/drm/drm_file.c |
ca00c2b9 JN |
210 | :doc: file operations |
211 | ||
b93658f8 DV |
212 | .. kernel-doc:: include/drm/drm_file.h |
213 | :internal: | |
214 | ||
9acdac68 | 215 | .. kernel-doc:: drivers/gpu/drm/drm_file.c |
ca00c2b9 JN |
216 | :export: |
217 | ||
d8187177 RC |
218 | Misc Utilities |
219 | ============== | |
220 | ||
221 | Printer | |
222 | ------- | |
223 | ||
224 | .. kernel-doc:: include/drm/drm_print.h | |
225 | :doc: print | |
226 | ||
227 | .. kernel-doc:: include/drm/drm_print.h | |
228 | :internal: | |
229 | ||
2d5e836d | 230 | .. kernel-doc:: drivers/gpu/drm/drm_print.c |
d8187177 RC |
231 | :export: |
232 | ||
233 | ||
ca00c2b9 | 234 | Legacy Support Code |
22554020 | 235 | =================== |
ca00c2b9 JN |
236 | |
237 | The section very briefly covers some of the old legacy support code | |
238 | which is only used by old DRM drivers which have done a so-called | |
239 | shadow-attach to the underlying device instead of registering as a real | |
240 | driver. This also includes some of the old generic buffer management and | |
241 | command submission code. Do not use any of this in new and modern | |
242 | drivers. | |
243 | ||
244 | Legacy Suspend/Resume | |
22554020 | 245 | --------------------- |
ca00c2b9 JN |
246 | |
247 | The DRM core provides some suspend/resume code, but drivers wanting full | |
248 | suspend/resume support should provide save() and restore() functions. | |
249 | These are called at suspend, hibernate, or resume time, and should | |
250 | perform any state save or restore required by your device across suspend | |
251 | or hibernate states. | |
252 | ||
253 | int (\*suspend) (struct drm_device \*, pm_message_t state); int | |
254 | (\*resume) (struct drm_device \*); | |
255 | Those are legacy suspend and resume methods which *only* work with the | |
256 | legacy shadow-attach driver registration functions. New driver should | |
257 | use the power management interface provided by their bus type (usually | |
258 | through the :c:type:`struct device_driver <device_driver>` | |
259 | dev_pm_ops) and set these methods to NULL. | |
260 | ||
261 | Legacy DMA Services | |
22554020 | 262 | ------------------- |
ca00c2b9 JN |
263 | |
264 | This should cover how DMA mapping etc. is supported by the core. These | |
265 | functions are deprecated and should not be used. |