[U-Boot-Users] Ideas on U-Boot configuration with FDT

Wolfgang Denk wd at denx.de
Sun May 20 11:33:35 CEST 2007

In message <46500875.6060706 at grandegger.com> you wrote:
> 	If defined, "fdt" is set to that address at compile time. The
>          FDT can be used from the early beginning of the boot.

Just nitpicking: maybe we should  call  this  CFG_FDT_ADDR_STATIC  or
CFG_FDT_ADDR_DEFAULT  or  CFG_FDT_ADDR_INIT  or  something like that.
Rationale: flash is just one of the  possible  storage  devies  -  it
could be ROM instead, or even RAM in certain configurations.

Also, while we are defining this, please keep in mind that sooner or
later someone will come up with the idea of storing the FDT in EEPROM,
so we might want to reserve such identifiers.

> 	If defined, the env variable "fdtaddr" is looked up early in the
>          boot and "fdt" is set accordingly. This allows to hold more than
>          one blob in FLASH and select one via env setting. This would
>          allow for _one_ combination of images of U-Boot + Linux + Blobs
>          for a _set_ of boards.

Traditionally, that should be named CFG_FDT_ADDR_IN_ENV

> 	If defined, the blob is moved to RAM after relocation for
>          further preparation or for performance reasons. "fdt" is re-set
>          accordingly. The blob is then ready and in place for booting
>          Linux. If CFG_FDT_ADDR_RAM is set to 0, the blob will be copied
> 	to a default location, e.g. before the initrd location.

I'm not sure I understand  this  -  will  CFG_FDT_ADDR_RAM  hold  the
*address*  in  RAM  where  the FDT gets copied to? That sounds pretty
static to me.

> A board-specific checkboad function is called as early as possible to 
> verify the FDT.

"checkboard()" is a name that can mean anything. If the  function  is
to  check  or  to  verify the FDT, the function name should represent
this, i. e. please  callit  checkfdt()  or  verifyfdt()  of  probably
fdtcheck() / fdtverify() or fdt_check() / fdt_verify().

Best regards,

Wolfgang Denk

DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
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Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
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