[U-Boot] CONFIG_MIPS_BOOT_CMDLINE_LEGACY usage ?

[Daniel Schwierzeck]

Hi Stefan,

On 15.08.2018 10:23, Stefan Roese wrote:
> Hi Daniel,
> 
> I'm wondering about the CONFIG_MIPS_BOOT_CMDLINE_LEGACY Kconfig
> option in MIPS. Why is this one called "legacy" and what should
> be used instead to pass the U-Boot bootargs to the Linux kernel?
> 
> Thanks,
> Stefan

This interface was initially added to U-Boot with MIPS support and is
copied from the MIPS Yamon bootloader. Dependent on the platform and the
used bootloader there are more different boot interfaces.

The modern way to boot a kernel on MIPS would be to add a DTB to the
kernel FIT image and let U-Boot pass it over to the kernel
(CONFIG_MIPS_BOOT_FDT). All bootargs would then be added automatically
to the /chosen/bootargs node. This interface is conformant with the MIPS
UHI boot protocol. The kernel supports this in a generic way. The PROM
code of a platform only needs to evaluate the fw_passed_dtb variable for
a DTB address. In your case the Ralink platform supports this.

But you still have the flexibility to use a DTB built-in or appended to
the kernel and pass the bootargs in the traditional way. The kernel has
various config options to select the source of bootargs.

-- 
- Daniel

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