Re: [Bug #11382] e1000e: 2.6.27-rc1 corrupts EEPROM/NVM

["H. Peter Anvin" <hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>]

Jiri Kosina wrote:
> 
> Yes, I think that xorg/xorg i915 driver/libdrm/GEM/whatever are the 
> biggest suspect currently, according to the data that has been gathered so 
> far.
> 
> Still, what confuses me a little bit -- the EEPROM of the card is set to 
> all 0xff, once the corruption happens. Isn't that a quite a coincidence, 
> that bytes representing "nothing" in this context are used?
> 

Typical card EEPROMs are serial - either I2C or SPI.  I believe the 
Intel cards use SPI EEPROMs, but I'm not sure.

[Disclaimer: I don't actually know SPI all that well; I know I2C better. 
  However, I'm pretty sure the following argument does apply to both.]

Consider a corruption which turns a read command into a write command -- 
often just a single bit difference.  Now, the EEPROM will expect data in 
to write, but nothing will be driving the data line, so it will 
typically be a 1.  As the host tries to read, it will therefore fill the 
EEPROM with all ones.

	-hpa