Linking Linux with root FS with OS loader - then transfer to FLASH

[jfs]

Posted on July 09, 2003 at 08:08

Linking Linux with root FS with OS loader - then transfer to FLASH

[jfs]

Posted on May 30, 2003 at 09:05

Hi,

We want to use the STPC elite booting Linux and the root FS out of FLASH. No BIOS, no disk. During boot time, Linux + root FS are transferred into RAM, then the FLASH is no longer used till next reboot.

Since BIOS is not used, we plan to use the provided OS loader. We will also get one STPC eval board, to developp the sw, while the actual HW design is worked on.

I am still not clear on:

1- On the Linux host system: How to link the Linux kernel (reCC'ed with 486 option) and the root FS with the provided OS loader.

2- How to transfer that image on the STPC eval board FLASH from the host

3- Linux is making BIOS calls during boot. Who will take care of that, since we dont want to use standard BIOS? Is that taken care of by your OS loader?

Could you point me to the right doc? I havent found it if it exists, sorry.

Are there any 3rd party BSPs? If so what are they?

Thanks a lot,

-jfsimon

[thierry239955_st]

Posted on June 03, 2003 at 15:20

3 - BIOS calls are not done by the Linux kernel or Linux applications but by the loader, LILO or GRUB, before to start the kernel. There is a good reason for this. At the very beginning of the kernel, the CPU switch from real to protected mode and is no more able to access the BIOS.

The only exception is VESA BIOS which include some functions designed for protected mode. This is used by VESA frame buffer device or XFree86 VESA driver for example. You won't be able to use all this graphics library if you use the STPC loader.

Farfalla

[thierry239955_st]

Posted on July 09, 2003 at 07:32

2 - for the loader debug phase, the best is to use an EPROM emulator you will connect in place of your flash. You download your code into the emulator from your host platform through parallel port, USB or ethernet.

You can take a look on Grammar Engine PromICE web-site (http://www.promice.com), for example.

Farfalla

[thierry239955_st]

Posted on July 09, 2003 at 08:08

1 - The access to the root FS is not a matter of the loader. The loader provide to the kernel the 'root=/dev/...' parameter on the command line then the kernel have to be well configured to be able to access the concerned device and file system.

In the example of the STPC Development Kit, the command is 'root=/dev/hdc4'. You need to have integrated into the kernel the ATAPI driver to be able to access the hard-disk and the ext2 file system to be able to understand the file system.

If you want to replace by NFS, for example, to get the FS through the network, you need to integrate the right network card drivers and NFS options then modify the command line in consequence.

I suggest you first verify your kernel is booting correctly with LILO or Grub before to test the new file system with the loader.

Farfalla