how to choice fallback or normal image?

[Terry B. Chen]

I read the code in cmos_failover.inc
But I don’t understand that RTC_BOOT_BYTE bit 1 gets the value from bit 0, the program clear bit 0 every time. But When to set the bit0 to 1, it will make the code jump to normal image next time?
I search 0x70(cmos index) in all but I cant find when set bit 0 to 1?

-----Original Message-----
From: steven james [mailto:pyro at linuxlabs.com] 
Sent: 2003年2月20日 23:27
To: Terry B. Chen
Cc: linuxbios at clustermatic.org
Subject: Re: how to choice fallback or normal image?

Greetings,


Several conditions need to exist for the primary image to be used. The
code looks at the RTC register to check for indication of power failure
(either battery dead, or clear CMOS jumper set), then the CMOS checksum is
checked. If both tests show that CMOS is valid, then check the
RTC_BOOT_BYTE. First, bit 0 is moved to bit 1 and bit 0 is cleared. Then,
if bit 1 is set, call the primary (normal image), That is done so that if
the boot fails for some reason, it will choose the fallback image next
time. It is also possible to cause a fallback boot by setting the clear
CMOS jumper.

The RTC_BOOT_BYTE is not included in the checksum since it will be changed
wi8th every boot.

Note that on some boards, the CMOS checksum is skipped.

G'day,
sjames


 The RTC_BOOT_BYTE 


On Thu, 20 Feb 2003, Terry B. Chen wrote:

> Dear all:
>          I was puzzled by the fallback and normal image in s2722
> (e7500), I am sorry to ask so simple question. When shall we use the
> fallback image and when shall we use the normal image? How you control
> which to run?
>          The register DRC (7c) bit 29(Init complete) seem not to be set
> after memory initialization complete. am I right?
> Thank you!
> 

-- 
-------------------------steven james, director of research, linux labs
... ........ ..... ....                     230 peachtree st nw ste 701
the original linux labs                             atlanta.ga.us 30303
      -since 1995                              http://www.linuxlabs.com
                                   office 404.577.7747 fax 404.577.7743
-----------------------------------------------------------------------