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Kernel Recipes 2013 - Overview display in the Linux kernel
The document discusses the issues and architecture surrounding display and graphic systems, highlighting challenges in processing such as rotation, scaling, and composition across various APIs like X11, Wayland, and DRM. It provides an overview of the history and evolution of display systems and their interfaces, along with a detailed examination of different memory management techniques, device models, and API documentation. Additionally, it analyzes cumulative changes in the API and drivers, presenting use cases for framebuffer devices and DRM/KMS frameworks.
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Kernel Recipes 2013 - Overview display in the Linux kernel
- 1. Display and Kernel Reviewand Future Kernel Recipes 2013 Paris Laurent Pinchart laurent.pinchart@ideasonboard.com
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- 7. Problem - Purpose display/ graphics / video
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- 11. Problem - Source format memory/ deep pipeline device / CPU
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- 27. Display – Scanout FrameBuffer
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- 35. Origins – FBDEV FBD EV,Linux 1.3.94 19962012 4C C Form ats 2000 Blanking
- 36. Origins – V4L2 V4L,Linux 2.2.0 19992002 2006 V4L2,Linux 2.4.0 V4L deprecated 2008 V4L2 subdev 2011 M edia controller videobuf2 2012 D M ABU F
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- 39. Memory Management DRM FBV4L2 Dynamic Allocation Yes No Yes Multiple Buffers Yes panning Yes Import dmabuf No userptr Export dmabuf mmap mmap mmap
- 40. Mode Setting DRM FBV4L2 Formats 4CC RGB 4CC 4CC Enumeration Planes No Yes Negotiation No No Yes Atomicity Yes No No
- 41. Transformations DRM FB V4L2 OverlaysYes No Yes Rotation Yes No Yes Scaling Yes No Yes Cropping/Panning Yes Yes Yes
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- 43. DRM API Documentation TheDRM core exports several interfaces to applications, generally intended to be used through corresponding libdrm wrapper functions. In addition, drivers export device-specific interfaces for use by userspace drivers & device-aware applications through ioctls and sysfs files. External interfaces include: memory mapping, context management, DMA operations, AGP management, vblank control, fence management, memory management, and output management. Cover generic ioctls and sysfs layout here. We only need high- level info, since man pages should cover the rest. “ „
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- 45. Code Size api coredrivers drm fb v4l2
- 46. Cumulative Changes -API 0 1000 2000 3000 4000 5000 6000 drm fb v4l2 drm fb v4l2
- 47. Cumulative Changes -Core 0 5000 10000 15000 20000 25000 30000 35000 40000 45000 50000 drm fb v4l2 drm fb v4l2
- 48. Cumulative Changes -Drivers 0 200000 400000 600000 800000 1000000 1200000 1400000 1600000 1800000 drm fb v4l2 drm fb v4l2
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- 50. Device Model –FBDEV Frame Buffer (memory) Display Device
- 51. Device Model –DRM/KMS Frame Buffer (memory) CRTC Encoder Connector Planes (memory) Encoder Connector Connector
- 52. Device Model –V4L2 Buffers (memory) Display Device Connector
- 53. Device Model –V4L2/MC V4L2 subdev 0 1 2 V4L2 subdev 0 1 V4L2 queue 0
- 54. Device Model –V4L2/MC
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- 56. Use Cases -FBDEV
- 57. Use Cases -FBDEV (that's it...)
- 58. Use Cases -V4L2 Video
- 59. Use Cases –DRM/KMS Everything else
- 60. FB vs. DRM- sloccount fbdev 0 500 1000 1500 2000 2500 2370
- 61. FB vs. DRM- sloccount fbdev drm 0 500 1000 1500 2000 2500 2370 1659
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- 63. KMS - DeviceModel Frame Buffer (memory) CRTC Encoder Connector Plane (memory) SoCMemory Off-Chip Encoder Connector
- 64. KMS – FrameBuffer CRTC Frame Buffer GEM Object(s) Memory ● width ● height ● format ● pitches ● offsets Properties
- 65. DRM/KMS – GEMObject CRTC Frame Buffer GEM Object ● width ● height ● bpp ● pitch ● size Properties Memory
- 66. DRM – Handles ProcessA Local Handle GEM Object Process B Send FD SCM_RIGHTS Global FD 1 2 Global FD 4 Local Handle 3
- 67. Active Area KMS – Modes(1/2) sync back porch front porch active area
- 68. Active Area KMS – Modes(2/2) sync back porch front porch active area hdisplay hsync_start htotal hsync_end
- 69. KMS – ModeSetting crtc fb Active Area x y mode.hdisplay mode.vdisplay *connectors num_connectors mode struct drm_mode_set { struct drm_framebuffer *fb; struct drm_crtc *crtc; struct drm_display_mode *mode; uint32_t x; uint32_t y; struct drm_connector **connectors; size_t num_connectors; };
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- 71. WIP – DisplayFramework Common Display Framework http://lwn.net/Articles/512363/
- 72. Entity Entity Link Port CDF -Entity Model
- 73. CDF - DeviceTree hdmi_encoder { ports { #address-cells = <1>; #size-cells = <0>; port@0 { hdmi_input: endpoint@0 { remote = <&display_output>; }; }; port@1 { endpoint@0 { ... }; endpoint@1 { ... }; }; }; };
- 74. Display Controller Video Entity Pipeline Controller controlcontrol Entity Entity CDF- Configuration Model
- 75. Display Controller Video Entity streaming control streaming control EntityEntity CDF - Streaming Control
- 76. CDF - Integration Display Controller Driver ControlBus API FBDEV DRM SPI/I2C Mem Map Panel Driver DT pdata DSI
- 77. • dri-devel@listsfreedesktop.org • linux-fbdev@vger.kernel.org •linux-media@vger.kernel.org • laurent.pinchart@ideasonboard.com Contact
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