[Linux-parport] Read Device ID of a parallel device

Nagesh A nagesha71 at gmail.com
Thu Jul 28 07:19:54 EDT 2011

Hi Tim,
Thank you for your reply.

Yes our driver is taking care.  Driver supports two ERV values:
1. nibble (0x00) and 2. device ID with nibble mode (0x04).

Actually, the negotiation is passed for the nibble mode (0x00) and is
performing rev.
data transfer successfully.

But, for device ID request, it is not the case, though the code execution
path is same
for both of them.

I could get the printk of ERV value - 0x04. and doing the following events:

1. set event 5 (Set XFlag, nDataAvail, PError low)
2. set event 6 (Set nAck high)
3. Wait for event 7 (HostBusy go low)
4. Data transfer phase

Above is the same sequence of execution even for the nibble mode data
Nibble mode data transfer is working fine.

-Nagesh A

On Thu, Jul 28, 2011 at 3:36 PM, Tim Waugh <twaugh at redhat.com> wrote:

> On Thu, 2011-07-28 at 14:41 +0530, Nagesh A wrote:
> > Currently my driver at device side, supports compatibility mode and
> > nibble mode, and
> > working fine with data transfers in both directions.
> To fetch the Device ID, the host sets bit 2 of the extensibility request
> value byte during negotiation (i.e. the byte placed on the data bits
> when nSelectIn/nAutoFd are toggled).
> Is your device watching for that?
> Tim.
> */

*-Nagesh A*
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