On Fri, Dec 10, 2010 at 01:44:20PM -0800, Greg KH wrote: > On Fri, Dec 10, 2010 at 10:23:31PM +0100, W. de Hoog wrote: > > >It uses LSR to see if the data is sent? That's a bit strange, but ok. > > Not that strange. The comments in mos7840.c suggest that this is the > > reason why they support it as well. > > Sorry, you are right, I was thinking of line settings like CTS/DTR, I > forgot that this was the actual number of characters left in the device > buffer. > > > >No, that wouldn't really work. What you need is the real TIOCSERGETLSR > > >support added to the driver, as it currently doesn't support it. > > > > > >Or you can go get a different device, as a few other usb to serial > > >devices do support TIOCSERGETLSR already. Those would be ones > > >controlled by the io_edgeport, mos7840, and mos7720 drivers. > > I only checked mos7840 and they use the result of the > > chars_in_buffer function. The ftdi_sio has one as well. > > > > Does this function return the number of characters in the PC buffer > > or in the ftdi usb chips buffer? So if it is 0 does it mean the data > > has been sent? > > That function shows the number of characters left in the PC buffer, not > the device's buffer. 0 means the data has been sent to the device, but > the UART in the device might still not have sent the data out. > > I don't know if the FTDI_SIO devices can report if their uarts are empty > or not (the io_edgeport devices can), perhaps someone else on this list > who is more familiar with that chiptype can let us know. Ah, it looks like it can report this information, see the TEMT (Transmitter Empty) flag in the ftdi_sio.h file. Can you test patches to the driver if I provide one to see if it works or not? thanks, greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
