[PATCH v3] docs: Correct FW_JUMP_FDT_ADDR calculation example

[Gabriel L. Somlo]

On Thu, Mar 30, 2023 at 10:15:59AM +0800, Xiang W wrote:
> 在 2023-03-24星期五的 08:07 -0400，Gabriel Somlo写道：
> > When using `PLATFORM=generic` defaults, the kernel is loaded at
> > `FW_JUMP_ADDR`, and the FDT is loaded at `FW_JUMP_FDT_ADDR.
> > 
> > Therefore, the maximum kernel size before `FW_JUMP_FDT_ADDR` must
> > be increased is `$(( FW_JUMP_FDT_ADDR - FW_JUMP_ADDR ))`.
> > 
> > The example calculation assumes `rv64`, and is wrong to boot
> > (off by 0x200000). Fix it and update it for the general case.
> > 
> > Signed-off-by: Gabriel Somlo <gsomlo at gmail.com>
> > ---
> >  docs/firmware/fw_jump.md | 16 ++++++++--------
> >  1 file changed, 8 insertions(+), 8 deletions(-)
> > 
> > diff --git a/docs/firmware/fw_jump.md b/docs/firmware/fw_jump.md
> > index 956897e..ed3a43e 100644
> > --- a/docs/firmware/fw_jump.md
> > +++ b/docs/firmware/fw_jump.md
> > @@ -46,15 +46,15 @@ follows:
> >    You can use the following method.
> >  
> >    ```
> > -  ${CROSS_COMPILE}objdump -h $KERNEL_ELF | sort -k 5,5 | awk -n '/^ +[0-9]+ /\
> > -  {addr="0x"$3; size="0x"$5; printf "0x""%x\n",addr+size}' \
> > -  | (( `tail -1` > 0x2200000 )) && echo fdt overlaps kernel,\
> > -  increase FW_JUMP_FDT_ADDR
> > +  ${CROSS_COMPILE}objdump -h $KERNEL_ELF | sort -k 5,5 | awk -n '
> > +  /^ +[0-9]+ / {addr="0x"$3; size="0x"$5; printf "0x""%x\n",addr+size}' |
> > +  (( `tail -1` > (FW_JUMP_FDT_ADDR - FW_JUMP_ADDR) )) &&
> FW_JUMP_FDT_ADDR and FW_JUMP_ADDR should be variables in the shell,
> and references need to use $ as the starting char.

AFAIK, "ARITHMETIC EVALUATION" rules in bash allow shell variables to
be referenced without the "parameter expansion syntax" (i.e., $FOO),
when they are within an expression (e.g., "(( FOO + BAR ))").

Thanks,
--Gabriel
 
> > +  echo fdt overlaps kernel, increase FW_JUMP_FDT_ADDR
> >  
> > -  ${LLVM}objdump -h --show-lma $KERNEL_ELF | sort -k 5,5 | \
> > -  awk -n '/^ +[0-9]+ / {addr="0x"$3; size="0x"$5; printf "0x""%x\n",addr+size}'\
> > -  | (( `tail -1` > 0x2200000 )) && echo fdt overlaps kernel,\
> > -  increase FW_JUMP_FDT_ADDR
> > +  ${LLVM}objdump -h --show-lma $KERNEL_ELF | sort -k 5,5 | awk -n '
> > +  /^ +[0-9]+ / {addr="0x"$3; size="0x"$5; printf "0x""%x\n",addr+size}' |
> > +  (( `tail -1` > (FW_JUMP_FDT_ADDR - FW_JUMP_ADDR) )) &&
> Same as above
> 
> Regards,
> Xiang W
> > +  echo fdt overlaps kernel, increase FW_JUMP_FDT_ADDR
> >    ```
> >  
> >  *FW_JUMP* Example
> > -- 
> > 2.39.2
> > 
> > 
>