[U-Boot] [PATCH/RFC] unify version_string

[Wolfgang Denk]

Dear =?UTF-8?q?Andreas=20Bie=C3=9Fmann?=,

In message <1308905261-3780-1-git-send-email-andreas.devel at googlemail.com> you wrote:
> This patch deletes the arch specific definitions of version_string in
> favour of a single one in cmd_version module (which is always compiled
> in).
> 
> Signed-off-by: Andreas Bießmann <andreas.devel at googlemail.com>
> CC: Mike Frysinger <vapier at gentoo.org>
> CC: Peter Pan <pppeterpppan at gmail.com>
> ---
> This is an RFC as discussed in
> http://mid.gmane.org/201106162022.09802.vapier@gentoo.org

Sorry, but NAK.  The idea is good, but the implementation is serioulsy
flawed.

...
> diff --git a/arch/powerpc/cpu/74xx_7xx/start.S b/arch/powerpc/cpu/74xx_7xx/start.S
> index f6011fc..5fea39d 100644
> --- a/arch/powerpc/cpu/74xx_7xx/start.S
> +++ b/arch/powerpc/cpu/74xx_7xx/start.S
...
>  	.text
>  	.long	0x27051956		/* U-Boot Magic Number		*/
> -	.globl	version_string
> -version_string:
> -	.ascii	U_BOOT_VERSION
> -	.ascii	" (", U_BOOT_DATE, " - ", U_BOOT_TIME, ")"
> -	.ascii	CONFIG_IDENT_STRING, "\0"

On PowerPC systems, the core is carefully consructed such that the
U-Boot image starts with the magic number, followed immediately by
the version string. That means, you can trivially identify any binary
image, be it as file on the host or on the target, or programmed into
flash, but just dumping the first bytes of it, for example:

On the host:

-> xd /tftpboot/tqm8560/u-boot.bin | head -5
       0  27051956 552d426f  6f742032 3031302e  |'  VU-Boot 2010.|
      10  31322d30 30313439  2d673662 31656632  |12-00149-g6b1ef2|
      20  612d6469 72747920  284d6179 20303420  |a-dirty (May 04 |
      30  32303131 202d2032  333a3439 3a343929  |2011 - 23:49:49)|
      40  00000000 00000000  00000000 00000000  |                |

On the target:

=> md FFFC0000 14
fffc0000: 27051956 552d426f 6f742032 3031302e    '..VU-Boot 2010.
fffc0010: 31322d30 30313439 2d673662 31656632    12-00149-g6b1ef2
fffc0020: 612d6469 72747920 284d6179 20303420    a-dirty (May 04 
fffc0030: 32303131 202d2032 333a3439 3a343929    2011 - 23:49:49)
fffc0040: 00000000 00000000 00000000 00000000    ................


I consider this a very useful property and am not willing to give it
up.

Best regards,

Wolfgang Denk

-- 
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