On Fri, Mar 18, 2005 at 11:24:37AM +0530, [EMAIL PROTECTED] wrote: > Hello, > > I am writing a driver for USB to Serial converter /bridge > having 4 serial ports . > > I was going through the existing USB to Serial driver . I > have a few questions related to those . I would be glad to > receive responses to my queries . > > 1. "num_interrupt_in" field in the usb_serial_device_type > structure is for the device and not for the port .
Yes. > I mean if there is a device which has INTERRUPT IN and BULK > OUT endpoints per port and has 4 such ports I would decalare > usb_serial_device_type with the fields poplulated as follows > .num_interrupt_in = 4, > .num_bulk_in = 0, > .num_bulk_out = 4, > .num_ports = 4, Yes. > 2. what are the tx Credits for the edgeport adapter ? I > really didnt get a feel of what it means . That's a device specific thing. It has to do with how the device handles how much room the device has left in its buffer. If your device doesn't have such a thing, don't worry about it. > 3. Do I need to maintain a buffer at the driver level . What > governs the desicion of having a buffer at the driver level. > In many sample drivers I found a separate buffer - e.g > pl2303.c , kobil_sct.c . It all depends on your device, and how fast you want the data to go through it, and fixing some fun tty corner cases where the usb-serial driver dropps data, but the tty layer doesn't think it was allowed to do that. See the archives for more details on this if you are curious. > I guess it should be a good since we can only transmit 64 > bytes ( maxPacketSize of endpoint ) in an URB and the > applications talking to serial device may send more bytes than these . Not necessarily, you can always return a short write, that's legal. It's when the above mentioned condition happens that you can not ignore it. > 4. What should be the criteria used to select the size of > the buffer . Whatever you think will work best. > 5. What is the significance of this step in "kobil_write()" > and "kobil_read_int_callback" > > // someone sets the dev to 0 if the close method has been called > port->interrupt_in_urb->dev = port->serial->dev; Don't really know. Hope this helps, greg k-h ------------------------------------------------------- SF email is sponsored by - The IT Product Guide Read honest & candid reviews on hundreds of IT Products from real users. Discover which products truly live up to the hype. Start reading now. http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
