Devdualcpu
From wiki.gp2x.org
This page is very (possibly extremely) old. If new information is available on this subject, then please add it to the wiki. However, this article may discuss a utility, game, emulator, development topic, or other subject that is no longer available, in development, applicable or useful to the wiki. If the subject of this article is still available or applicable, then please remove this notice. On the other hand, this page may be submitted for Proposed Deletion if this notice is not taken down by another user.
Additional notes may be shown below. Please discuss this message on the article's Talk Page.
Additional notes may be shown below. Please discuss this message on the article's Talk Page.
Contents |
Introduction
The /dev/dualcpu character device is the official way of interacting with the 940t. It only provides video decoding functions. It is not a general purpose interface. At present it seems only MPEG4 decoding functions are provided, with provision for H263, MJPEG and MPEG2 decoding, as well as MPEG4 encoding.
Communication is achieved through a serials of ioctl calls to the device. Reading from the device gives it's status as a single byte.
Documentation
The only current documentation is in the form of the source release from November, 2005.
The relevent files are:
drivers/char/dualcpu.h drivers/char/dualcpu.c drivers/char/vpp.h drivers/char/vpp.c
You can view them in the cvs repository by going to http://cvs.sourceforge.net/viewcvs.py/open2x/linux-mmsp2/drivers/char/#dirlist
Call Sequence
This information is derived from the strace below.
open /dev/dualcpu as dualcpu ioctl dualcpu IOCTL_DUALCPU_MP4D_INIT ioctl dualcpu IOCTL_DUALCPU_MP4D_INIT_BUF times 6
while playing video:
ioctl dualcpu IOCTL_DUALCPU_MP4D_RUN
read status
if status == 21:
draw frame
end if
end while
strace
The following seems to be the call sequence that mplayer in firmware 1.1 makes to /dev/dualcpu
fd 13 is /dev/dualcpu fd 14 is /dev/vpp - video post processor
Intialization
open("/dev/dualcpu", O_RDWR) = 13
open("/dev/vpp", O_RDWR) = 14
ioctl(14, 0x7630, 0) = 0 --- this one appears to be undocumented
ioctl(13, IOCTL_DUALCPU_MP4D_INIT, 0x157bf4) = 1
read(13, "\5", 32) = 1
ioctl(13, IOCTL_DUALCPU_MP4D_INIT_BUF, 0x157c14) = 1
read(13, "\5", 32) = 1
ioctl(13, IOCTL_DUALCPU_MP4D_INIT_BUF, 0x157c14) = 1
read(13, "\5", 32) = 1
ioctl(13, IOCTL_DUALCPU_MP4D_INIT_BUF, 0x157c14) = 1
read(13, "\5", 32) = 1
ioctl(13, IOCTL_DUALCPU_MP4D_INIT_BUF, 0x157c14) = 1
read(13, "\5", 32) = 1
ioctl(13, IOCTL_DUALCPU_MP4D_INIT_BUF, 0x157c14) = 1
read(13, "\5", 32) = 1
ioctl(13, IOCTL_DUALCPU_MP4D_INIT_BUF, 0x157c14) = 1
read(13, "\5", 32) = 1 --- how does it know when to stop buffering ?
ioctl(14, OCTL_MMSP2_SET_FDC, 0x157c58) = 0
ioctl(14, IOCTL_MMSP2_SET_SC, 0x157ca0) = 0
ioctl(14, IOCTL_MMSP2_SET_YUVA, 0x157c74) = 0
ioctl(14, IOCTL_MMSP2_YUVA_OFF, 0) = 0
ioctl(14, IOCTL_MMSP2_YUVB_OFF, 0) = 0
Video Decoding
ioctl(13, IOCTL_DUALCPU_MP4D_RUN, 0x157c20) = 1 read(13, "\2", 32) = 1 ioctl(13, IOCTL_DUALCPU_MP4D_RUN, 0x157c20) = 1 read(13, "\2", 32) = 1 ioctl(13, IOCTL_DUALCPU_MP4D_RUN, 0x157c20) = 1 read(13, "\2", 32) = 1 ioctl(13, IOCTL_DUALCPU_MP4D_RUN, 0x157c20) = 1 read(13, "\21", 32) = 1 ioctl(13, IOCTL_DUALCPU_MP4D_RUN, 0x157c20) = 1 read(13, "\2", 32) = 1 ioctl(13, IOCTL_DUALCPU_MP4D_RUN, 0x157c20) = 1 read(13, "\2", 32) = 1 ioctl(13, IOCTL_DUALCPU_MP4D_RUN, 0x157c20) = 1 read(13, "\2", 32) = 1 ioctl(13, IOCTL_DUALCPU_MP4D_RUN, 0x157c20) = 1 read(13, "\21", 32) = 1 ioctl(14, IOCTL_MMSP2_START_FDC, 0x15b308) = 0 ioctl(14, IOCTL_MMSP2_START_SC, 0x2) = 0 ioctl(14, IOCTL_MMSP2_SC_BUSY, 0) = 0 ioctl(13, IOCTL_DUALCPU_MP4D_RUN, 0x157c20) = 1 read(13, "\2", 32) = 1 ioctl(13, IOCTL_DUALCPU_MP4D_RUN, 0x157c20) = 1 read(13, "\2", 32) = 1 ioctl(13, IOCTL_DUALCPU_MP4D_RUN, 0x157c20) = 1 read(13, "\2", 32) = 1 ioctl(13, IOCTL_DUALCPU_MP4D_RUN, 0x157c20) = 1 read(13, "\2", 32) = 1 ioctl(13, IOCTL_DUALCPU_MP4D_RUN, 0x157c20) = 1 read(13, "\2", 32) = 1 ioctl(13, IOCTL_DUALCPU_MP4D_RUN, 0x157c20) = 1 read(13, "\21", 32) = 1 ioctl(14, IOCTL_MMSP2_START_FDC, 0x15b308) = 0 ioctl(14, IOCTL_MMSP2_START_SC, 0x2) = 0 ioctl(14, IOCTL_MMSP2_SC_BUSY, 0) = 0 ioctl(13, IOCTL_DUALCPU_MP4D_RUN, 0x157c20) = 1 read(13, "\2", 32) = 1 ioctl(13, IOCTL_DUALCPU_MP4D_RUN, 0x157c20) = 1 read(13, "\2", 32) = 1 ioctl(13, IOCTL_DUALCPU_MP4D_RUN, 0x157c20) = 1 read(13, "\21", 32) = 1 ioctl(14, IOCTL_MMSP2_START_FDC, 0x15b308) = 0 ioctl(14, IOCTL_MMSP2_START_SC, 0x2) = 0 ioctl(14, IOCTL_MMSP2_SC_BUSY, 0) = 0 ioctl(14, VIDIOCSYNC, 0) = 0 ioctl(13, IOCTL_DUALCPU_MP4D_RUN, 0x157c20) = 1 read(13, "\2", 32) = 1 ioctl(13, IOCTL_DUALCPU_MP4D_RUN, 0x157c20) = 1 read(13, "\2", 32) = 1 ioctl(13, IOCTL_DUALCPU_MP4D_RUN, 0x157c20) = 1 read(13, "\21", 32) = 1 ioctl(14, IOCTL_MMSP2_START_FDC, 0x15b308) = 0 ioctl(14, IOCTL_MMSP2_START_SC, 0x2) = 0 ioctl(14, IOCTL_MMSP2_SC_BUSY, 0) = 0 ioctl(13, IOCTL_DUALCPU_MP4D_RUN, 0x157c20) = 1 read(13, "\21", 32) = 1 ioctl(14, IOCTL_MMSP2_START_FDC, 0x15b308) = 0 ioctl(14, IOCTL_MMSP2_START_SC, 0x2) = 0 ioctl(14, IOCTL_MMSP2_SC_BUSY, 0) = 0 ioctl(13, IOCTL_DUALCPU_MP4D_RUN, 0x157c20) = 1 read(13, "\2", 32) = 1 ioctl(13, IOCTL_DUALCPU_MP4D_RUN, 0x157c20) = 1 read(13, "\2", 32) = 1 ioctl(13, IOCTL_DUALCPU_MP4D_RUN, 0x157c20) = 1 read(13, "\2", 32) = 1 ioctl(13, IOCTL_DUALCPU_MP4D_RUN, 0x157c20) = 1 read(13, "\21", 32) = 1 ioctl(14, IOCTL_MMSP2_START_FDC, 0x15b308) = 0 ioctl(14, IOCTL_MMSP2_START_SC, 0x2) = 0 ioctl(14, IOCTL_MMSP2_SC_BUSY, 0) = 0 ioctl(13, IOCTL_DUALCPU_MP4D_RUN, 0x157c20) = 1 read(13, "\21", 32) = 1 ioctl(14, IOCTL_MMSP2_START_FDC, 0x15b308) = 0 ioctl(14, IOCTL_MMSP2_START_SC, 0x2) = 0 ioctl(14, IOCTL_MMSP2_SC_BUSY, 0) = 0 ioctl(13, IOCTL_DUALCPU_MP4D_RUN, 0x157c20) = 1 read(13, "\2", 32) = 1
