[U-Boot] bootstopkey reason behind it

[Wolfgang Denk]

Dear Paavaanan_T_N at Dell.com,

In message <D5A6F3355F664C40AFB65BB1277D8D450193B22639 at MAAX7MCDC101.APAC.DELL.COM> you wrote:
>
> To stop autoboot we have 2 ifdef (CONFIG_AUTOBOOT_STOP_ [STR2 ||
> STR1] ). Which is very easy and straightforward to implement. Halting
> a boot with single "Keystroke" is having its own advantages to the
> user. But, why multiple key support is ignored say like [ctrl +
> anykey ] combination. Especially, BIOS vendors prefer at least
> simultaneous pressing of 2 or more keys to halt the boot. Any
> specific reasons to avoid this. Other than simplicity is there any
> specific reason to stick on this.

BIOSes and BIOS compatible extension cards (say, PCI controllers) are
usually a major PITA when you are not working in an environment where
you have a real keyboard attached.  We're dealing with embedded
devices here, and often we have only communication paths like a serial
port (eventually even over a modem line), or netconsole.

Have you ever tried to transmit some "ALT + some_key" control
sequences over a serial port?

> I mean why simultaneous two key press support is avoided and
> implemented a secondary bootstopkey to halt the boot say like
> CONFIG_AUTOBOOT_STOP_STR2.

This is done because usually we do not have a real keyboard.  So
anything that cannot be mapped into the standard ASCII character set
cannot be used here.

Best regards,

Wolfgang Denk

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