[U-Boot] style issue: ft_board_setup() versus ft_verify_fdt()?

[Robert P. J. Day <rpjday@crashcourse.ca>]

  curious about recommended coding style related to modifying and
verifying FDTs ... i'm perusing common/image-fdt.c and can see the
order of (possible) operations here in the function
image_setup_libfdt():

 * arch_fixup_fdt()
 * ft_board_setup()
 * ft_system_setup()
 * fdt_fixup_ethernet()
   ... etc etc ...
 * ft_verify_fdt()

where an earlier comment explains that last routine:

/*
 * Verify the device tree.
 *
 * This function is called after all device tree fix-ups have been enacted,
 * so that the final device tree can be verified.  The definition of "verified"
 * is up to the specific implementation.  However, it generally means that the
 * addresses of some of the devices in the device tree are compared with the
 * actual addresses at which U-Boot has placed them.
 *
 * Returns 1 on success, 0 on failure.  If 0 is returned, U-Boot will halt the
 * boot process.
 */
__weak int ft_verify_fdt(void *fdt)
{
        return 1;
}


  which seems reasonable ... after you've mangled your FDT in every
way you need, optionally supply a routine to make sure it looks sane.

  however, for the freescale board mpc8641hpcn.c, here's part of the
ft_board_setup() routine (actually, this is pretty much all that
function does):


        if (tmp) {
                u64 addr;

                if (addrcells == 1)
                        addr = *(u32 *)tmp;
                else
                        addr = *tmp;

                if (addr != CONFIG_SYS_CCSRBAR_PHYS)
                        printf("WARNING: The CCSRBAR address in your .dts "
                               "does not match the address of the CCSR "
                               "in u-boot.  This means your .dts might "
                               "be old.\n");
        }

so the board setup routine is doing some quick sanity checking, which
is perfectly fine, but seems to be exactly the sort of thing
ft_verify_fdt() was designed for.

  obviously, one can add sanity checking to any of those routines
depending on how early you want to notice stuff -- is there somewhere
a style guide that gives recommendations? just looking for "best
practices," thanks.

  i'm sure there will be more FDT-related questions coming ... thank
you for your patience.

rday

-- 

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Robert P. J. Day                                 Ottawa, Ontario, CANADA
                        http://crashcourse.ca

Twitter:                                       http://twitter.com/rpjday
LinkedIn:                               http://ca.linkedin.com/in/rpjday
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