/* -*- eval: c_set_style("linux") -*- */ /* * Driver for the arkmicro 3116 usb2serial convertor chip. * * (C) Copyright 2009 by Bart Hartgers (bart.hartgers+ark3116@gmail.com) * * 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. * * This driver is a 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. * * Some concepts and code borrowed from Simon Schulz' original ark3116.c. * * * 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 * Free Software Foundation; either version 2 of the License, or (at your * option) any later version. * */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #define ARK_DEBUG 0 /* * Version information */ #define DRIVER_VERSION "v0.2" #define DRIVER_AUTHOR "Bart Hartgers " #define DRIVER_DESC "USB ARK3116 serial/IrDA driver" #define DRIVER_DEV_DESC "ARK3116 RS232/IrDA" #define DRIVER_NAME "ark3116new" /* usb timeout of 1 second */ #define ARK_TIMEOUT 1*HZ static struct usb_device_id ark_id_table [] = { { USB_DEVICE(0x6547, 0x0232) }, /* RS232 */ { USB_DEVICE(0x18ec, 0x3118) }, /* USB to IrDA */ { } }; static int debug=ARK_DEBUG; MODULE_DEVICE_TABLE(usb, ark_id_table); struct ark_private { /* for handling sleeping while waiting for * msr change to happen */ wait_queue_head_t delta_msr_wait; struct async_icount icount; int irda; /* 1 for irda device */ /* protects hw register updates */ struct mutex lock; int quot; /* baudrate divisor */ __u8 lcr; /* line control register value */ __u8 hcr; /* handshake control register (0x8) * value */ /* flags - updated asynchronously */ atomic_t mcr; /* mcr value */ atomic_t msr; atomic_t lsr; }; static int ark_write_reg( struct usb_serial *serial, unsigned reg, __u8 val ) { int result; /* 0xfe 0x40 are magic values taken from original ark3116.c */ result = usb_control_msg( serial->dev, usb_sndctrlpipe(serial->dev,0), 0xfe, 0x40, val, reg, NULL, 0, ARK_TIMEOUT ); return result; } static int ark_read_reg( struct usb_serial *serial, unsigned reg, unsigned char *buf ) { int result; /* 0xfe 0xc0 are magic values taken from original ark3116.c */ 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 ark_atomic_set_clear( unsigned set, unsigned clear, atomic_t *at ) { if ((clear==0) && (set==0)) return; #if defined(atomic_set_mask) if (clear==0) { atomic_set_mask( set, at ); return; } #endif #if defined(atomic_clear_mask) if (set==0) { atomic_clear_mask( clear, at ); return; } #endif /* operation needs to be atomic */ for(;;) { register unsigned old=atomic_read( at ); register unsigned prev=atomic_cmpxchg( at, old, (old|set)&(~clear) ); if (likely(prev==old)) break; } } static void ark_update_msr( struct usb_serial_port *port, __u8 msr ) { struct ark_private *priv = usb_get_serial_port_data(port); atomic_set(&priv->msr, msr ); if (msr & UART_MSR_ANY_DELTA) { /* update input line counters */ if (msr & UART_MSR_DCTS) priv->icount.cts++; if (msr & UART_MSR_DDSR) priv->icount.dsr++; if (msr & UART_MSR_DDCD) priv->icount.dcd++; if (msr & UART_MSR_TERI) priv->icount.rng++; wake_up_interruptible(&priv->delta_msr_wait); } #if 0 /* Handle CTS flow control. * I am not sure if this is really necessary: * Because of hw handshake, the write URB will simply block * when CTS is deasserted */ if (msr & UART_MSR_CTS) { struct tty_struct *tty = tty_port_tty_get(&port->port); if (tty && C_CRTSCTS(tty)) tty_wakeup(tty); tty_kref_put(tty); } #endif } static void ark_combine_lsr( struct usb_serial_port *port, __u8 lsr ) { struct ark_private *priv = usb_get_serial_port_data(port); /* combine bits */ ark_atomic_set_clear( lsr, 0, &priv->lsr ); if (lsr&UART_LSR_BRK_ERROR_BITS) { if (lsr & UART_LSR_BI) priv->icount.brk++; if (lsr & UART_LSR_FE) priv->icount.frame++; if (lsr & UART_LSR_PE) priv->icount.parity++; if (lsr & UART_LSR_OE) priv->icount.overrun++; } } static void ark_break_ctl( struct tty_struct *tty, int break_state ) { struct usb_serial_port *port = tty->driver_data; struct ark_private *priv = usb_get_serial_port_data(port); /* LCR is also used for other things: protect access */ mutex_lock( &priv->lock ); if (break_state) priv->lcr|=UART_LCR_SBC; else priv->lcr&=UART_LCR_SBC; ark_write_reg( port->serial, UART_LCR, priv->lcr ); mutex_unlock( &priv->lock ); } inline int calc_divisor( int bps ) { /* Original ark3116 made some exceptions in rounding here * because windows did the same. Assume that is not really * necessary. * Crystal is 12MHz, probably because of USB, but we divide by 4? */ return (12000000 + 2*bps) / (4*bps); } static void ark_set_termios( struct tty_struct *tty, struct usb_serial_port *port, struct ktermios *old_termios) { struct usb_serial *serial = port->serial; struct ark_private *priv = usb_get_serial_port_data(port); struct ktermios *termios = tty->termios; unsigned cflag=termios->c_cflag; int bps = tty_get_baud_rate(tty); int quot; __u8 lcr, hcr, eval; /* set data bit count */ switch(cflag & CSIZE) { case CS5: lcr=UART_LCR_WLEN5; break; case CS6: lcr=UART_LCR_WLEN6; break; case CS7: lcr=UART_LCR_WLEN7; break; default: case CS8: lcr=UART_LCR_WLEN8; break; } if (cflag & CSTOPB) lcr |= UART_LCR_STOP; if (cflag & PARENB) lcr |= UART_LCR_PARITY; if (!(cflag & PARODD)) lcr |= UART_LCR_EPAR; #ifdef CMSPAR if (cflag & CMSPAR) lcr |= UART_LCR_SPAR; #endif /* handshake control */ hcr = (cflag & CRTSCTS) ? 0x03 : 0x00; /* calc baudrate */ dbg("%s - setting bps to %d",__func__,bps); eval = 0; switch(bps) { case 0: quot = calc_divisor(9600); break; default: if ((bps<75) || (bps>3000000)) { bps = 9600; } quot = calc_divisor( bps ); break; case 460800: eval = 1; quot = calc_divisor( bps ); break; case 921600: eval = 2; quot = calc_divisor( bps ); break; } /* Update state: synchronize */ mutex_lock( &priv->lock ); /* keep old LCR_SBC bit */ lcr|=(priv->lcr & UART_LCR_SBC); dbg("%s - setting hcr:0x%02x,lcr:0x%02x,quot:%d", __func__, hcr, lcr, quot ); /* handshake control */ if (priv->hcr!=hcr) { priv->hcr=hcr; ark_write_reg( serial, 0x8, hcr ); } /* baudrate */ if (priv->quot!=quot) { priv->quot=quot; priv->lcr=lcr; /* need to write lcr anyway */ /* disable DMA since transmit/receive is * shadowed by UART_DLL */ ark_write_reg( serial, UART_FCR, 0 ); ark_write_reg( serial, UART_LCR, lcr|UART_LCR_DLAB); ark_write_reg( serial, UART_DLL, quot & 0xff ); ark_write_reg( serial, UART_DLM, (quot>>8) & 0xff ); /* restore lcr */ ark_write_reg( serial, UART_LCR, lcr ); /* magic baudrate thingy: not sure what it does, * but windows does this as well. */ ark_write_reg( serial, 0xe, eval ); /* enable DMA */ ark_write_reg( serial, UART_FCR, UART_FCR_DMA_SELECT ); } else if (priv->lcr!=lcr) { priv->lcr=lcr; ark_write_reg( serial, UART_LCR, lcr ); } mutex_unlock( &priv->lock ); /* check for software flow control */ if (I_IXOFF(tty) || I_IXON(tty)) { dev_warn( &serial->dev->dev, "%s: don't know how to do software flow control\n", KBUILD_MODNAME ); } /* Don't rewrite B0 */ if (tty_termios_baud_rate(termios)) tty_termios_encode_baud_rate(termios, bps, bps); } static int ark_tiocmget(struct tty_struct *tty, struct file *file) { struct usb_serial_port *port = tty->driver_data; struct ark_private *priv = usb_get_serial_port_data(port); /* read modem status */ unsigned status = atomic_read( &priv->msr ); /* modem control is output */ unsigned ctrl = atomic_read( &priv->mcr ); return (status & UART_MSR_DSR ? TIOCM_DSR : 0) | (status & UART_MSR_CTS ? TIOCM_CTS : 0) | (status & UART_MSR_RI ? TIOCM_RI : 0) | (status & UART_MSR_DCD ? TIOCM_CD : 0) | (ctrl & UART_MCR_DTR ? TIOCM_DTR : 0) | (ctrl & UART_MCR_RTS ? TIOCM_RTS : 0) | (ctrl & UART_MCR_OUT1 ? TIOCM_OUT1 : 0) | (ctrl & UART_MCR_OUT2 ? TIOCM_OUT2 : 0); } static int ark_tiocmset(struct tty_struct *tty, struct file *file, unsigned set, unsigned clr) { struct usb_serial_port *port = tty->driver_data; struct ark_private *priv = usb_get_serial_port_data(port); unsigned setmask=0; unsigned clrmask=0; if (set & TIOCM_RTS) setmask|=UART_MCR_RTS; if (set & TIOCM_DTR) setmask|=UART_MCR_DTR; if (set & TIOCM_OUT1) setmask|=UART_MCR_OUT1; if (set & TIOCM_OUT2) setmask|=UART_MCR_OUT2; if (clr & TIOCM_RTS) clrmask|=UART_MCR_RTS; if (clr & TIOCM_DTR) clrmask|=UART_MCR_DTR; if (clr & TIOCM_OUT1) clrmask|=UART_MCR_OUT1; if (clr & TIOCM_OUT2) clrmask|=UART_MCR_OUT2; ark_atomic_set_clear( setmask, clrmask, &priv->mcr ); /* unfortunately, we need the mutex, to make sure that the value * in priv->mcr is actually the one in the hardware */ mutex_lock( &priv->lock ); ark_write_reg( port->serial, UART_MCR, atomic_read(&priv->mcr) ); mutex_unlock( &priv->lock ); return 0; } static void ark_read_int_callback( struct urb *urb ) { struct usb_serial_port *port = urb->context; int status = urb->status; const __u8 *data=urb->transfer_buffer; int result; switch (status) { case -ECONNRESET: case -ENOENT: case -ESHUTDOWN: /* this urb is terminated, clean up */ dbg("%s - urb shutting down with status: %d", __func__, status); return; default: dbg("%s - nonzero urb status received: %d", __func__, status); break; case 0: /* success */ /* discovered this by trail and error... */ if ((urb->actual_length==4) && (data[0]==0xe8)) { const __u8 id=data[1]&UART_IIR_ID; dbg("%s: iir=%02x",__func__,data[1]); if (id==UART_IIR_MSI) { dbg("%s: msr=%02x",__func__,data[3]); ark_update_msr( port, data[3] ); break; } else if (id==UART_IIR_RLSI) { dbg("%s: lsr=%02x",__func__,data[2]); ark_combine_lsr( port, data[2] ); break; } } /* * Not sure what this does yet... */ usb_serial_debug_data( debug, &port->dev, __func__, urb->actual_length, urb->transfer_buffer); break; } result = usb_submit_urb(urb, GFP_ATOMIC); if (result) dev_err(&urb->dev->dev, "%s - Error %d submitting interrupt urb\n", __func__, result); } /* Data comes in via the bulk (data) URB, erors/interrupts via the int URB. * This means that we cannot be sure which data byte has an associated error * condition, so we report an error for all data in the next bulk read. * * Actually, there might even be a window between the bulk data leaving the * ark and reading/resetting the lsr in the read_bulk_callback where an * interrupt for the next data block could come in. * Without somekind of handshaking on the ark, we would have to report the * error for the next block of data as well... * For now, let's pretend this can't happen. */ static void send_to_tty( struct tty_struct *tty, const unsigned char *chars, size_t size, char flag ) { if (size==0) return; if (flag == TTY_NORMAL) { tty_insert_flip_string(tty, chars, size); } else { int i; for(i=0; icontext; struct ark_private *priv = usb_get_serial_port_data(port); const __u8 *data = urb->transfer_buffer; int status = urb->status; struct tty_struct *tty; unsigned long flags; int result; char flag; __u8 lsr; switch (status) { case -ECONNRESET: case -ENOENT: case -ESHUTDOWN: /* this urb is terminated, clean up */ dbg("%s - urb shutting down with status: %d", __func__, status); return; default: dbg("%s - nonzero urb status received: %d", __func__, status); break; case 0: /* success */ lsr = atomic_read(&priv->lsr); ark_atomic_set_clear( 0, UART_LSR_BRK_ERROR_BITS, &priv->lsr ); /* Throttle the device if requested by tty */ spin_lock_irqsave(&port->lock, flags); port->throttled = port->throttle_req; if (port->throttled) { spin_unlock_irqrestore(&port->lock, flags); return; } else spin_unlock_irqrestore(&port->lock, flags); if (unlikely(lsr & UART_LSR_BI)) flag = TTY_BREAK; else if (unlikely(lsr & UART_LSR_PE)) flag = TTY_PARITY; else if (unlikely(lsr & UART_LSR_FE)) flag = TTY_FRAME; else flag = TTY_NORMAL; tty = tty_port_tty_get(&port->port); if (tty) { tty_buffer_request_room(tty, urb->actual_length + 1); /* overrun is special, not associated with a char */ if (unlikely(lsr & UART_LSR_OE)) tty_insert_flip_char(tty, 0, TTY_OVERRUN); send_to_tty(tty, data, urb->actual_length, flag ); tty_flip_buffer_push(tty); tty_kref_put(tty); } } /* Continue reading from device */ #if 0 /* does not seem to be needed */ usb_fill_bulk_urb(urb, port->serial->dev, usb_rcvbulkpipe(port->serial->dev, port->bulk_in_endpointAddress), urb->transfer_buffer, urb->transfer_buffer_length, ark_read_bulk_callback, port); #endif result = usb_submit_urb(urb, GFP_ATOMIC); if (result) dev_err(&urb->dev->dev, "%s - failed resubmitting" " read urb, error %d\n", __func__, result); } static int ark_ioctl(struct tty_struct *tty, struct file *file, unsigned int cmd, unsigned long arg) { struct usb_serial_port *port = tty->driver_data; struct ark_private *priv = usb_get_serial_port_data(port); switch(cmd) { case TIOCMIWAIT: for(;;) { struct async_icount prev=priv->icount; interruptible_sleep_on(&priv->delta_msr_wait); /* see if a signal did it */ if (signal_pending(current)) return -ERESTARTSYS; if ((prev.rng==priv->icount.rng) && (prev.dsr==priv->icount.dsr) && (prev.dcd==priv->icount.dcd) && (prev.cts==priv->icount.cts)) return -EIO; if ((arg & TIOCM_RNG && (prev.rng!=priv->icount.rng)) || (arg & TIOCM_DSR && (prev.dsr!=priv->icount.dsr)) || (arg & TIOCM_CD && (prev.dcd!=priv->icount.dcd)) || (arg & TIOCM_CTS && (prev.cts!=priv->icount.cts))) return 0; } break; case TIOCGICOUNT: { struct serial_icounter_struct icount; struct async_icount cnow=priv->icount; memset(&icount, 0, sizeof(icount)); icount.cts = cnow.cts; icount.dsr = cnow.dsr; icount.rng = cnow.rng; icount.dcd = cnow.dcd; icount.rx = cnow.rx; icount.tx = cnow.tx; icount.frame = cnow.frame; icount.overrun = cnow.overrun; icount.parity = cnow.parity; icount.brk = cnow.brk; icount.buf_overrun = cnow.buf_overrun; if (copy_to_user((void __user *)arg, &icount, sizeof(icount))) return -EFAULT; return 0; } } return -ENOIOCTLCMD; } static void ark_close( struct usb_serial_port *port ) { struct usb_serial *serial = port->serial; /* disable DMA */ ark_write_reg( serial, UART_FCR, 0 ); /* deactivate interrupts */ ark_write_reg( serial, UART_IER, 0 ); if (serial->dev) { /* shutdown any bulk reads that might be going on */ if (serial->num_bulk_out) usb_kill_urb(port->write_urb); if (serial->num_bulk_in) usb_kill_urb(port->read_urb); if (serial->num_interrupt_in) usb_kill_urb(port->interrupt_in_urb); } } static int ark_open(struct tty_struct *tty, struct usb_serial_port *port, struct file *filp) { struct ark_private *priv = usb_get_serial_port_data(port); struct usb_serial *serial = port->serial; int result; unsigned char *buf; buf = kmalloc( 4, GFP_KERNEL ); if (buf==NULL) return -ENOMEM; result = usb_serial_generic_open(tty, port, filp); if (result) { dbg("%s - usb_serial_generic_open failed: %d", __func__, result ); goto error_out; } /* setup termios */ if (tty) ark_set_termios(tty, port, NULL ); /* remove any data still left: also clears error state */ ark_read_reg( serial, UART_RX, buf ); /* read modem status */ atomic_set( &priv->msr, ark_read_reg( serial, UART_MSR, buf ) ); /* read line status */ atomic_set( &priv->lsr, ark_read_reg( serial, UART_LSR, buf ) ); result = usb_submit_urb(port->interrupt_in_urb, GFP_KERNEL); if (result) { dev_err(&port->dev, "submit irq_in urb failed %d\n", result); ark_close( port ); goto error_out; } /* activate interrupts */ ark_write_reg( port->serial, UART_IER, UART_IER_MSI|UART_IER_RLSI ); /* enable DMA */ ark_write_reg( port->serial, UART_FCR, UART_FCR_DMA_SELECT ); error_out: kfree(buf); return result; } static int ark_is_irda( struct usb_serial *serial ) { __u16 vendor = le16_to_cpu(serial->dev->descriptor.idVendor); __u16 product = le16_to_cpu(serial->dev->descriptor.idProduct); if ((product==0x3118) && (vendor==0x18ec)) return 1; return 0; } static int ark_attach( struct usb_serial *serial ) { struct usb_serial_port *port=serial->port[0]; struct ark_private *priv; /* make sure we have our end-points */ if ((serial->num_bulk_in==0) || (serial->num_bulk_out==0) || (serial->num_interrupt_in==0)) { dev_err( &serial->dev->dev, "%s - missing endpoint - " "bulk in: %d, bulk out: %d, int in %d\n", KBUILD_MODNAME, serial->num_bulk_in, serial->num_bulk_out, serial->num_interrupt_in ); return -EINVAL; } priv = kzalloc( sizeof(struct ark_private), GFP_KERNEL); if (!priv) return -ENOMEM; init_waitqueue_head(&priv->delta_msr_wait); mutex_init(&priv->lock); priv->irda = ark_is_irda( serial ); usb_set_serial_port_data(port, priv); /* setup the hardware */ ark_write_reg( serial, UART_IER, 0 ); /* disable DMA */ ark_write_reg( serial, UART_FCR, 0 ); /* handshake control */ priv->hcr = 0; ark_write_reg( serial, 0x8 , 0 ); /* modem control */ atomic_set( &priv->mcr, 0 ); ark_write_reg( serial, UART_MCR, 0 ); if (priv->irda==0) { ark_write_reg( serial, 0xb , 0 ); } else { ark_write_reg( serial, 0xb , 1 ); ark_write_reg( serial, 0xc , 0 ); ark_write_reg( serial, 0xd , 0x41 ); ark_write_reg( serial, 0xa , 0x01 ); } /* setup baudrate */ ark_write_reg( serial, UART_LCR, UART_LCR_DLAB ); /* setup for 9600 8N1 */ priv->quot=calc_divisor( 9600 ); ark_write_reg( serial, UART_DLL, priv->quot & 0xff ); ark_write_reg( serial, UART_DLM, (priv->quot>>8) & 0xff ); priv->lcr = UART_LCR_WLEN8; ark_write_reg( serial, UART_LCR, UART_LCR_WLEN8 ); ark_write_reg( serial, 0x0e , 0 ); if (priv->irda) { ark_write_reg( serial, 0x9 , 0 ); } dev_info( &serial->dev->dev, "%s using %s mode\n", KBUILD_MODNAME, priv->irda ? "IrDA" : "RS232" ); return 0; } static void ark_release( struct usb_serial *serial ) { struct usb_serial_port *port=serial->port[0]; struct ark_private *priv = usb_get_serial_port_data(port); /* device is closed, so URBs and DMA should be down */ usb_set_serial_port_data(port, NULL ); mutex_destroy( &priv->lock ); kfree( priv ); } static struct usb_driver ark_driver = { .name = DRIVER_NAME, .probe = usb_serial_probe, .disconnect = usb_serial_disconnect, .id_table = ark_id_table, .no_dynamic_id = 1, }; static struct usb_serial_driver ark_device = { .driver = { .owner = THIS_MODULE, .name = DRIVER_NAME, }, .description = DRIVER_DEV_DESC, .id_table = ark_id_table, .usb_driver = &ark_driver, .num_ports = 1, .attach = ark_attach, .release = ark_release, .set_termios = ark_set_termios, .tiocmget = ark_tiocmget, .tiocmset = ark_tiocmset, .ioctl = ark_ioctl, .open = ark_open, .close = ark_close, .break_ctl = ark_break_ctl, .read_int_callback = ark_read_int_callback, .read_bulk_callback = ark_read_bulk_callback, }; static int __init ark_init(void) { int retval; retval = usb_serial_register(&ark_device); if (retval==0) { retval = usb_register(&ark_driver); if (retval==0) { printk( KERN_INFO "%s:" DRIVER_VERSION ":" DRIVER_DESC "\n", KBUILD_MODNAME ); return retval; } usb_serial_deregister(&ark_device); } return retval; } static void __exit ark_exit(void) { usb_deregister(&ark_driver); usb_serial_deregister(&ark_device); } module_init(ark_init); module_exit(ark_exit); MODULE_AUTHOR(DRIVER_AUTHOR); MODULE_DESCRIPTION(DRIVER_DESC); MODULE_LICENSE("GPL"); module_param(debug, bool, S_IRUGO | S_IWUSR); 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 */