USB: ark3116: Setup some basic infrastructure for new ark3116 driver.

Signed-off-by: Bart Hartgers <bart.hartgers@gmail.com>
Cc: Mike McCormack <mikem@ring3k.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/serial/ark3116.c

 /*
+ * Copyright (C) 2009 by Bart Hartgers (bart.hartgers+ark3116@gmail.com)
+ * Original version:
  * Copyright (C) 2006
  *   Simon Schulz (ark3116_driver <at> auctionant.de)
  *
@@ -6,10 +8,13 @@
  * - implements a driver for the arkmicro ark3116 chipset (vendor=0x6547,
  *   productid=0x0232) (used in a datacable called KQ-U8A)
  *
- * - based on code by krisfx -> thanks !!
- *   (see http://www.linuxquestions.org/questions/showthread.php?p=2184457#post2184457)
+ * Supports full modem status lines, break, hardware flow control. Does not
+ * support software flow control, since I do not know how to enable it in hw.
  *
- *  - based on logs created by usbsnoopy
+ * This driver is a essentially new implementation. I initially dug
+ * into the old ark3116.c driver and suddenly realized the ark3116 is
+ * a 16450 with a USB interface glued to it. See comments at the
+ * bottom of this file.
  *
  * This program is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License as published by the
@@ -19,15 +24,31 @@
 
 #include <linux/kernel.h>
 #include <linux/init.h>
+#include <linux/ioctl.h>
 #include <linux/tty.h>
+#include <linux/tty_flip.h>
 #include <linux/module.h>
 #include <linux/usb.h>
 #include <linux/usb/serial.h>
 #include <linux/serial.h>
+#include <linux/serial_reg.h>
 #include <linux/uaccess.h>
-
+#include <linux/mutex.h>
+#include <linux/spinlock.h>
 
 static int debug;
+/*
+ * Version information
+ */
+
+#define DRIVER_VERSION "v0.5"
+#define DRIVER_AUTHOR "Bart Hartgers <bart.hartgers+ark3116@gmail.com>"
+#define DRIVER_DESC "USB ARK3116 serial/IrDA driver"
+#define DRIVER_DEV_DESC "ARK3116 RS232/IrDA"
+#define DRIVER_NAME "ark3116"
+
+/* usb timeout of 1 second */
+#define ARK_TIMEOUT (1*HZ)
 
 static struct usb_device_id id_table [] = {
 	{ USB_DEVICE(0x6547, 0x0232) },
@@ -45,6 +66,53 @@ static int is_irda(struct usb_serial *serial)
 	return 0;
 }
 
+struct ark3116_private {
+	wait_queue_head_t       delta_msr_wait;
+	struct async_icount	icount;
+	int			irda;	/* 1 for irda device */
+
+	/* protects hw register updates */
+	struct mutex		hw_lock;
+
+	int			quot;	/* baudrate divisor */
+	__u32			lcr;	/* line control register value */
+	__u32			hcr;	/* handshake control register (0x8)
+					 * value */
+	__u32			mcr;	/* modem contol register value */
+
+	/* protects the status values below */
+	spinlock_t		status_lock;
+	__u32			msr;	/* modem status register value */
+	__u32			lsr;	/* line status register value */
+};
+
+static int ark3116_write_reg(struct usb_serial *serial,
+			     unsigned reg, __u8 val)
+{
+	int result;
+	 /* 0xfe 0x40 are magic values taken from original driver */
+	result = usb_control_msg(serial->dev,
+				 usb_sndctrlpipe(serial->dev, 0),
+				 0xfe, 0x40, val, reg,
+				 NULL, 0, ARK_TIMEOUT);
+	return result;
+}
+
+static int ark3116_read_reg(struct usb_serial *serial,
+			    unsigned reg, unsigned char *buf)
+{
+	int result;
+	/* 0xfe 0xc0 are magic values taken from original driver */
+	result = usb_control_msg(serial->dev,
+				 usb_rcvctrlpipe(serial->dev, 0),
+				 0xfe, 0xc0, 0, reg,
+				 buf, 1, ARK_TIMEOUT);
+	if (result < 0)
+		return result;
+	else
+		return buf[0];
+}
+
 static inline void ARK3116_SND(struct usb_serial *serial, int seq,
 			       __u8 request, __u8 requesttype,
 			       __u16 value, __u16 index)
@@ -465,7 +533,12 @@ static int __init ark3116_init(void)
 	if (retval)
 		return retval;
 	retval = usb_register(&ark3116_driver);
-	if (retval)
+	if (retval == 0) {
+		printk(KERN_INFO "%s:"
+		       DRIVER_VERSION ":"
+		       DRIVER_DESC "\n",
+		       KBUILD_MODNAME);
+	} else
 		usb_serial_deregister(&ark3116_device);
 	return retval;
 }
@@ -480,6 +553,109 @@ module_init(ark3116_init);
 module_exit(ark3116_exit);
 MODULE_LICENSE("GPL");
 
+MODULE_AUTHOR(DRIVER_AUTHOR);
+MODULE_DESCRIPTION(DRIVER_DESC);
+
 module_param(debug, bool, S_IRUGO | S_IWUSR);
-MODULE_PARM_DESC(debug, "Debug enabled or not");
+MODULE_PARM_DESC(debug, "Enable debug");
 
+/*
+ * The following describes what I learned from studying the old
+ * ark3116.c driver, disassembling the windows driver, and some lucky
+ * guesses. Since I do not have any datasheet or other
+ * documentation, inaccuracies are almost guaranteed.
+ *
+ * Some specs for the ARK3116 can be found here:
+ * http://web.archive.org/web/20060318000438/
+ *   www.arkmicro.com/en/products/view.php?id=10
+ * On that page, 2 GPIO pins are mentioned: I assume these are the
+ * OUT1 and OUT2 pins of the UART, so I added support for those
+ * through the MCR. Since the pins are not available on my hardware,
+ * I could not verify this.
+ * Also, it states there is "on-chip hardware flow control". I have
+ * discovered how to enable that. Unfortunately, I do not know how to
+ * enable XON/XOFF (software) flow control, which would need support
+ * from the chip as well to work. Because of the wording on the web
+ * page there is a real possibility the chip simply does not support
+ * software flow control.
+ *
+ * I got my ark3116 as part of a mobile phone adapter cable. On the
+ * PCB, the following numbered contacts are present:
+ *
+ *  1:- +5V
+ *  2:o DTR
+ *  3:i RX
+ *  4:i DCD
+ *  5:o RTS
+ *  6:o TX
+ *  7:i RI
+ *  8:i DSR
+ * 10:- 0V
+ * 11:i CTS
+ *
+ * On my chip, all signals seem to be 3.3V, but 5V tolerant. But that
+ * may be different for the one you have ;-).
+ *
+ * The windows driver limits the registers to 0-F, so I assume there
+ * are actually 16 present on the device.
+ *
+ * On an UART interrupt, 4 bytes of data come in on the interrupt
+ * endpoint. The bytes are 0xe8 IIR LSR MSR.
+ *
+ * The baudrate seems to be generated from the 12MHz crystal, using
+ * 4-times subsampling. So quot=12e6/(4*baud). Also see description
+ * of register E.
+ *
+ * Registers 0-7:
+ * These seem to be the same as for a regular 16450. The FCR is set
+ * to UART_FCR_DMA_SELECT (0x8), I guess to enable transfers between
+ * the UART and the USB bridge/DMA engine.
+ *
+ * Register 8:
+ * By trial and error, I found out that bit 0 enables hardware CTS,
+ * stopping TX when CTS is +5V. Bit 1 does the same for RTS, making
+ * RTS +5V when the 3116 cannot transfer the data to the USB bus
+ * (verified by disabling the reading URB). Note that as far as I can
+ * tell, the windows driver does NOT use this, so there might be some
+ * hardware bug or something.
+ *
+ * According to a patch provided here
+ * (http://lkml.org/lkml/2009/7/26/56), the ARK3116 can also be used
+ * as an IrDA dongle. Since I do not have such a thing, I could not
+ * investigate that aspect. However, I can speculate ;-).
+ *
+ * - IrDA encodes data differently than RS232. Most likely, one of
+ *   the bits in registers 9..E enables the IR ENDEC (encoder/decoder).
+ * - Depending on the IR transceiver, the input and output need to be
+ *   inverted, so there are probably bits for that as well.
+ * - IrDA is half-duplex, so there should be a bit for selecting that.
+ *
+ * This still leaves at least two registers unaccounted for. Perhaps
+ * The chip can do XON/XOFF or CRC in HW?
+ *
+ * Register 9:
+ * Set to 0x00 for IrDA, when the baudrate is initialised.
+ *
+ * Register A:
+ * Set to 0x01 for IrDA, at init.
+ *
+ * Register B:
+ * Set to 0x01 for IrDA, 0x00 for RS232, at init.
+ *
+ * Register C:
+ * Set to 00 for IrDA, at init.
+ *
+ * Register D:
+ * Set to 0x41 for IrDA, at init.
+ *
+ * Register E:
+ * Somekind of baudrate override. The windows driver seems to set
+ * this to 0x00 for normal baudrates, 0x01 for 460800, 0x02 for 921600.
+ * Since 460800 and 921600 cannot be obtained by dividing 3MHz by an integer,
+ * it could be somekind of subdivisor thingy.
+ * However,it does not seem to do anything: selecting 921600 (divisor 3,
+ * reg E=2), still gets 1 MHz. I also checked if registers 9, C or F would
+ * work, but they don't.
+ *
+ * Register F: unknown
+ */