Re: Potential problem with reading data from usb devices with ugen(4)

[Brian Buhrow <buhrow%nfbcal.org@localhost>]

On Nov 5,  9:07pm, Nick Hudson wrote:
} Subject: Re: Potential problem with reading data from usb devices with uge
} On 05/11/2015 18:53, Brian Buhrow wrote:
} > 	Hello.  I've been making progress on this issue and have now run into
} > another issue which folks may be able to shed some light on.
} >
} > 	I've modified the ugen(4) driver to read from devices asynchronously
} > using a callout, allowing me to issue non-blocking read requests and fixing
} > poll(9) so it actually works as expected. 
} 
} You shouldn't need this. Adjust the code to keep a read transfer alive 
} at all times.

	I'm not sure I understand what your saying.  If I just keep
perpetuating the transfer without the callout, don't I have to wait until
the transfer is done before returning to the user process? Right now, with
my patches, I'll return partial data, or no data to the user but then
continue collecting data from the device, signaling the user with
poll/select acknowledgement when the transfer is finally done.  What I want
is an almost immediate return from the read(2) call without any delay.
Doesn't your suggestion ensure that doesn't happen?  I'm not trying to
argue, just trying to understand so I have something commitable at the end.

	
} 
} See USBD_FORCE_SHORT_XFER - ugen needs to be taught about it.

	Ok, but how do I get a 0-length write request down to the ugen(4)
driver in the first place?  That's the part that doesn't seem to be making
it.

-thanks

-Brian