[sane-devel] Epson SX600FW support

[Olaf Meeuwissen]

Alessandro Zummo <azummo-lists at towertech.it> writes:

> On Wed, 14 Jan 2009 19:33:54 -0600
> Chris Bagwell <chris at cnpbagwell.com> wrote:
>
>> But google turned up a PDF of some other random Epson scanner that shows 
>> the length of identity2 response.  The patch at the end of this email 
>> specifies the response length and also fixes the issue.  As I've spent a 
>> grand total of 1 hour on researching this so far, I do not know enough 
>> yet to decide if the length is the real fix (and safe for all scanners) 
>> or disabling the call like you did is right (esci_request_identity() 
>> also uses a zero length but is wrapped by a != SANE_EPSON_NET to prevent 
>> similar error).
>
>  Hi,
>
>   iirc the length can be different for each scanner model, but I might
>  be wrong. I've been a little busy but will try to research the issue.

Correct.  The identity2 command (ESC i) uses the same handshake as the
identity command (ESC I).

  - send 2 byte command
  - read 4 byte info block
  - compute size of upcoming data block from info block
    (n = info[2] | info[3] << 8)
  - read n byte data block

The size of the data block is model specific.

There are more commands that use this handshake, e.g. ESC f.

Hope this helps,
-- 
Olaf Meeuwissen, LPIC-2           FLOSS Engineer -- AVASYS Corporation
FSF Associate Member #1962               Help support software freedom
                 http://www.fsf.org/jf?referrer=1962