drm/kms, fb and v4l2: how to select a graphics and video api · how to select a graphics and video...
TRANSCRIPT
DRM/KMS, FB and V4L2:How to Select a Graphics and
Video API
Embedded Linux Conference Europe 2012
Laurent [email protected]
Disclaimer
Personal opinion
Flame war possibleHandle with care
Problem Definition
Problem Definition
Problem - Purpose
display / graphics / video
Problem - Source
formatmemory / deep pipeline
device / CPU
Problem - Processing
rotationscaling
composing
Problem - Stack
X11WaylandDirectFBRaw API
Problem - API
DRMFBDEVV4L2
Origins
Origins – DRM/KMS
2000
DRM, L
inux 2
.2.1
8
2009
KMS, T
TM
2008
GEMPlan
es, D
MABUF
2011 2012
Dumb
Buffe
rs
Origins – V4L2
V4L, L
inux 2
.2.0
1999 2002 2006
V4L2,
Linu
x 2.4
.0
V4L d
epre
cate
d
2008
V4L2
subd
ev
2011
Med
ia co
ntro
ller
video
buf2
2012
DMABUF(?
)
Origins – FBDEV
FBDEV, L
inux 1
.3.9
4
1996 2012
4CC F
orm
ats
2000
Blankin
g
Features
Memory Management
DRM FB V4L2
Dynamic Allocation Yes No Yes
Multiple Buffers Yes panning Yes
Import dmabuf No userptr
Exportdmabufmmap
mmap mmap
Mode Setting
DRM FB V4L2
Formats 4CCRGB4CC
4CC
Enumeration Planes No Yes
Negotiation No No Yes
Atomicity Yes No No
Transformations
DRM FB V4L2
Overlays Yes No Yes
Rotation Yes No Yes
Scaling Yes No Yes
Cropping/Panning Yes Yes Yes
Documentation
api core drivers
drmfbv4l2
DRM API Documentation
The DRM 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.
“
„
Documentation
api core drivers
drmfbv4l2
Code Size
api core drivers
drmfbv4l2
Cumulative Changes - API
v2.6.12v2.6.14
v2.6.16v2.6.18
v2.6.20v2.6.22
v2.6.24v2.6.26
v2.6.28v2.6.30
v2.6.32v2.6.34
v2.6.36v2.6.38
v3.0v3.2
v3.4v3.6-rc3
0
500
1000
1500
2000
2500
3000
3500
4000
drm
fb
v4l2
drmfbv4l2
Cumulative Changes - Core
v2.6.12v2.6.14
v2.6.16v2.6.18
v2.6.20v2.6.22
v2.6.24v2.6.26
v2.6.28v2.6.30
v2.6.32v2.6.34
v2.6.36v2.6.38
v3.0v3.2
v3.4v3.6-rc3
0
5000
10000
15000
20000
25000
30000
35000
40000
45000
drm
fb
v4l2
drmfbv4l2
Cumulative Changes - Drivers
v2.6.12v2.6.14
v2.6.16v2.6.18
v2.6.20v2.6.22
v2.6.24v2.6.26
v2.6.28v2.6.30
v2.6.32v2.6.34
v2.6.36v2.6.38
v3.0v3.2
v3.4v3.6-rc3
0
100000
200000
300000
400000
500000
600000
700000
800000
900000
1000000
drm
fb
v4l2
drmfbv4l2
Mailing List Traffic
2009-112010-01
2010-032010-05
2010-072010-09
2010-112011-01
2011-032011-05
2011-072011-09
2011-112012-01
2012-032012-05
2012-07
0
200
400
600
800
1000
1200
1400
1600
drmfbv4l2drm+bug
Device Model – FBDEV
Frame Buffer(memory)
DisplayDevice
Device Model – DRM/KMS
Frame Buffer(memory) CRTC Encoder Connector
Plane(memory)
Device Model – V4L2
Buffers(memory)
DisplayDevice
Connector
Device Model – V4L2/MC
V4L2subdev
0
1
2V4L2
subdev0 1
V4L2queue
0
Device Model – V4L2/MC
Use Cases
FB vs. DRM - sloccount
fbdev0
500
1000
1500
2000
2500
2370
FB vs. DRM - sloccount
fbdev drm0
500
1000
1500
2000
2500
2370
1659
Use Cases - FBDEV
Use Cases - FBDEV
(that's it...)
Use Cases - V4L2
Video
Use Cases – DRM/KMS
Everything else
KMS – Device Model
Frame Buffer(memory) CRTC Encoder Connector
Plane(memory)
SoCMemory Off-Chip
KMS – Frame Buffer
CRTC
Frame Buffer
GEMObject(s)
Memory
● width● height● format● pitches● offsets
Properties
DRM/KMS – GEM Object
CRTC
Frame Buffer
GEM Object
● width● height● bpp● pitch● size
Properties
Memory
DRM – Handles
Process A
LocalHandle
GEMObject
Process B
Send FDSCM_RIGHTS
GlobalFD
1 2Global
FD4
LocalHandle
3
Source: http://www.flickr.com/photos/buckaroobay/3721809183/
Work In Progress
panel & backlighthttp://lwn.net/Articles/512363/
WIP – Display Framework
DPI/LVDSDISPC PanelDSI/LVDS
Panel Module
PanelController
Transmitter
? !
thx.