Backchannel usage

Josh Mathis josh.m at swecoinus.com
Mon May 22 12:00:40 PDT 2006


Michael Sweet wrote:
> Josh Mathis wrote:
>> One quick update - I tried this with a USB printer, and the result was 
>> different. I wrote the same status request and read the same way. The 
>> read returned -1. However, watching a tail of the error_log, AFTER my 
>> filter was done, and the read returned -1, I get a debug message from 
>> the USB backend saying that it received 2 bytes of backchannel data. I 
>> changed my filter to timeout after 10 seconds on the read, then issue 
>> another read. The second one comes back correctly, with the right data 
>> from the printer. I have also tried excessive timeouts like 2 minutes, 
>> but get the same result - the first read always fails.
>>
>> So this raises two questions - why does the parallel backend not get 
>> anything at all back, and why does the USB get the return data too late?
> 
> What OS?
> 

This is Linux 2.6.15-23 on a Kubuntu Dapper system. (I know, I know...)




More information about the cups-devel mailing list