Testing of the Raspberry Pi graphic support

[Pavel Pisa]

Hello Qiao Yang,

On Thursday 02 of July 2015 01:23:24 桥 杨 wrote:
> >
> > The final - RTEMS-4.11 intended option for i386 is named video
> >
> >  --video=auto|off|1024x768-32
> >
> > console selection is controlled by option
> >
> >  --console=com1
>
>  I tried to retrieve ATAG cmdline by mailbox property tag  channel, but
> failed as it cannot asure the string is terminated by certain
> character('/0') and I didn't fix the implementation of tag structure at
> that moment. It reminds me that I should take some time back to it, and
> maybe the freebsd, rasbian's source code can do help. I've just found some
> posts on arm atags . I'll look into the detail and try to implement it this
> weekend.

The access to ATAGs should be solved directly from RTEMS.
ATAGs. The structure is directly pointed by r2 register
when loader jumps to RTEMS for legacy boot. FDT address
is passed to the kernel in r2 for device tree case and command
line is filled to FDT in this case.

So r2 value should be preserved after enter to RTEMS
binary and pinted memory analyzed later.

See

4a. Setup the kernel tagged list

https://www.kernel.org/doc/Documentation/arm/Booting

Linux kernel ATAGs cmdline parsing is implemented in

http://lxr.free-electrons.com/source/arch/arm/include/uapi/asm/setup.h
http://lxr.free-electrons.com/source/arch/avr32/kernel/setup.c#L381

If r2 points to 0xd00dfeed (FDT_MAGIC) then FDT data are pointed by r2.
Format 

http://lxr.free-electrons.com/source/scripts/dtc/libfdt/fdt.h#L44

parsing

http://lxr.free-electrons.com/source/scripts/dtc/libfdt/fdt.c#L60

Best wishes,

             Pavel