On Wednesday 23 May 2007, Linux OneAccess wrote:
I was figuring out how to pass board info from U-Boot to Linux and I saw that Linux references the bd_info structure.
I'm not sure, however, which definition to use: In U-Boot, struct bd_info is defined in include/asm/u-boot.h In Linux, it's defined in include/asm-ppc/ppcboot.h.
These two are somewhat different (different #ifdefs) which means the first few members (RAM size and such) are the same, but from then on it can diverge.
Yes, this is quite a mess. One of the reasons that this bd_info structure will "die" with the end of the arch/ppc support in the Linux kernel (I assume you know of the arch/ppc -> arch/powerpc merge). In arch/powerpc another mechanism is used to pass information from the bootloader to the linux kernel.
Furthermore, in Linux there are several boards that define their own structure for this. Should we use the ppcboot.h definition, or is it there an intention to push the u-boot.h to the Linux tree one day?
This depends on the PPC platform you are using. What PPC platform are you talking about? MPC8xx, PPC4xx? MPC8xxx is quite dead in arch/ppc already for example and you should start your board port in arch/powerpc. If it's PPC4xx, then you should probably still use bd_info in arch/ppc, and it really doesn't matter how you hack the bd_info in the kernel, since it has to be moved to arch/powerpc in the future anyway. I would suggest to define a "own" board specific bd_info for now, to not pollute the asm-ppc/ppcboot.h with further #ifdefs.
Hope this helps.
Best regards, Stefan
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