[U-Boot-Users] Re: FT u-boot shim

Kumar Gala galak at kernel.crashing.org
Thu Apr 27 21:40:42 CEST 2006

On Apr 27, 2006, at 2:30 PM, Rune Torgersen wrote:

> Would it be possible to have the kernel smart enough that if it gets
> passed a bd_t pointer, it updates the dts before booting fully.
> Newer u-boot versions that support dts then would pass a NULL bd_t
> pointer to a kernel that supports dts. Kernel would then not update  
> the
> dts, but use the one it gets handed.

What you are describing is the boot shim method.

U-boot is already capable of effectively doing this.  You can set a u- 
boot environment variable to make bootm do different things if you  
have flat device tree support built into u-boot.

> bootm should be able to see if the kernel has an attached dts,  
> update it
> with runtime parameters, and hand it off to the kernel. If it is an  
> old
> kernel, hand it the bd_t pointer.

We can do this w/o too much modification to what is happening in u- 
boot today.  I'd probably like to keep the ability to build a dev  
tree into the u-boot binary, but make the preferred means to pass a  
blob into the bootm command.

- kumar

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