Re: Using framebuffer device under Linux

[Lawrence <lawrencio@hotpop.com>]

Hi Frederic,

Thanks for your reply. I did some more research after my post, and 
finally I can initialise the framebuffer under Red Hat 9.

I must pass something like "vga=788" as the kernel parameter to grub so 
that it will use /dev/fb0, "vga=ask" will change the mode you gave after 
boot up, but will immedately shift back to text mode when initialization 
script start.

Hoever, the asm program 'fb' still doesn't work...

Anyway, I'll try to consult the kernel doc you've mentioned.

Thanks again,
Lawrence

Frederic Marmond ??:

> (re)Hi Lawrence! ;)
>
> I don't know about the FB managment in linuxassembly, but here is some 
> points you can have a look regarding FB:
> - kernel may have support for FB already compiled in (see the kernel 
> .config, and check that FB_ options are correctly setted)
> - if kernel has the FB support, have a look at the kernel parameters 
> (append="video=something" in your lilo.conf)
> - you can also have a look at /var/log/messages
> - to see if FB is already working, have a look at the '/proc' (mount 
> /proc;cat /proc/fb)
> - to access FB, open/write to /dev/fb0
> - to use kernel driver fb routines, use ioctl to /dev/fb0
> - read documentation about the driver in /usr/src/linux/Documentation 
> (if the kernel sources are installed, and if the kernel you run was 
> compiled there)
> - you can use the VESA driver (less optimised than a specific FB 
> driver, but often work). Use the "vga=mode" parameter in your lilo to 
> activate it.
>
>
> To access the frame buffer as a large memory, you must use *mmap* in 
> C. I don't know how it may be called in assembly under Linux, but this 
> may be a start for you.
> mmap will be used to map the device /dev/fb0 into memory. So, you may 
> access the FB with assembly mov, very easily, as a 'standard' memory 
> region.
>
>
> Regards,
> Fred
>
>
> Lawrence wrote:
>
>> Hi All,
>>
>> I am planning to do graphic with asm under Linux without X11. I am try
>> to use framebuffer as the "drawing plane".
>>
>> I've reached the article entitled "Using the framebuffer device under
>> Linux" within http://linuxassembly.org and I've extracted and compiled
>> fb.n according to the instruction. However, when I run "fb" under the
>> console in RH9, I only got a refresh and then back to the text console.
>>
>> I've tried fb under the installation environment of Debian 3.0, with I
>> thought it is already in framebuffer mode, but still got a failure.
>>
>>
>> I've tried ald fb, but when it is going to switch to framebuffer mode,
>> Linux squeeze and I have to telnet into my linux box using another
>> machine and issue a reboot...
>>
>> I can successfully run "leaves" under a-linux however, but I don't know
>> how to put fb under a-linux so as to see if it works, as there seems no
>> way to mount a floppy or access ethernet under a-linux.
>>
>> Would anyone be so kind as to tell me how could I access linux
>> framebuffer correcely using assembly, or point me out the forgettable
>> steps in order to run 'fb' successfully?
>>
>> my 'nasm -r' command spit out:
>>
>> NASM version 0.98.22 compiled on Sep 19 2003
>>
>> Thanks
>> Lawrence
>>
>>
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