Re: vpd query

[Mario da Costa <mario@controlnet.co.in>]

yang.can.mei@philips.com wrote:
> 
> Hi there,
> 
> For a multiple function device, we know the first function header type has to be set 0x8x, but what about the other functions' header types of this same device? should we set their hearder types as 0x8x also?
> 
> thanks
> 
> Paul Yang C.M.
> Philips Semiconductors


Hello,
Thanks for your reply, however I think you have misunderstood my doubt.
I am copying and pasting my previous mail below. I am pretty clear about
how the VPD registers are accessed through the CApabilities list. What
baffles me is how the data transfer will take place between the VPD
hardware device and the system. Especially after a read operation, when
the harware device sets the flag to 1 to indicate that the system can
now read the data, what happens when the system wants to write to the
VPD device ? If the flag is already 1, then will this not lead to some
confusion ??? Especially if the system wants to write data immediately
after it reads the VPD data.




Part of my previous mail is below :
<snip>
You are familiar with the procedure to read and write the VPD data.
Supposing Software is reading the data, it writes the VPD address (how
does it know this address i.e. what to write in the VPD address register
????) and sets the flag to zero.

hardware fetches the data  places it in the VPD data reg, then it sets
the flag to one.

software will see this flag as one, then read the data. 

my doubt is after this what happens to the flag ?? will it remain one
and if it does, will the hardware on seeing this one assume that now the
software wants to write VPD data ? Will this not lead to some amount of
confusion. ??
<snip>






TIA,
Best Regards,
mario

-- 
..... in life, there is more imagination
         than in all our dreams .....