USB: usbserial: mos7720: add support for parallel port on moschip 7715

Add support for the parallel port on the moschip MCS7715 device.  The port
registers itself with the parport subsystem as a low-level driver.  A separate
entry to the kernel configuration is added beneath that for the mos7720, to
avoid the need to link with the parport subsystem code for users who don't have
or don't want the parallel port.  Only compatibility mode is currently supported
(no ECP/EPP).  Tested with both moschip devices (7720 and 7715) on UP and SMP
hosts, including regression testing of serial port, concurrent operation of
serial and parallel ports, and various connect / disconnect scenarios.

Signed-off-by: Mike Dunn <mikedunn@newsguy.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 16 insertions, 0 deletions

diff --git a/Documentation/usb/usb-serial.txt b/Documentation/usb/usb-serial.txt
index 540c91ccf86f..f4d214510259 100644
--- a/Documentation/usb/usb-serial.txt
+++ b/Documentation/usb/usb-serial.txt
@@ -440,6 +440,22 @@ Winchiphead CH341 Driver
   For any questions or problems with this driver, please contact
   frank@kingswood-consulting.co.uk.
 
+Moschip MCS7720, MCS7715 driver
+
+  These chips are present in devices sold by various manufacturers, such as Syba
+  and Cables Unlimited.  There may be others.  The 7720 provides two serial
+  ports, and the 7715 provides one serial and one standard PC parallel port.
+  Support for the 7715's parallel port is enabled by a separate option, which
+  will not appear unless parallel port support is first enabled at the top-level
+  of the Device Drivers config menu.  Currently only compatibility mode is
+  supported on the parallel port (no ECP/EPP).
+
+  TODO:
+    - Implement ECP/EPP modes for the parallel port.
+    - Baud rates higher than 115200 are currently broken.
+    - Devices with a single serial port based on the Moschip MCS7703 may work
+      with this driver with a simple addition to the usb_device_id table.  I
+      don't have one of these devices, so I can't say for sure.
 
 Generic Serial driver