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

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

On Sep 24, 12:00pm, Nick Hudson wrote:
} Are you sure about this? I'm not sure why ugen_bulkra_intr doesn't start 
} a new transfer, but see below.
} 
} I wonder if
} 
}          http://nxr.netbsd.org/xref/src/sys/dev/usb/ugen.c#697
}          http://nxr.netbsd.org/xref/src/sys/dev/usb/ugen.c#1221
} 
} needs USBD_SHORT_XFER_OK adding to the flags arg.
} 
} UGEN_DEBUG output will help?
} 
} Nick

	I forgot to mention the libusb1 calls do request the
USB_SET_SHORT_XFER via ioctl(2).  

	The general problem seems to be that if the file descriptor is in
non-blocking mode and there's no data to read when a read call is made,
there's no asynchronous mechanism to poll the device for data once the read
call has told the user process that the process would block if it tried to
read.  If that's true, then asynchronous reading just can't work in the
current code.  My question is, what am I missing or is this really the
case?  If it is the case, what's the best way to solve it?
-thanks
-Brian

>-- End of excerpt from Nick Hudson