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/* $Id: ieee1284.c,v 1.1.1.1 2004-04-15 02:29:15 phoenix Exp $

 * IEEE-1284 implementation for parport.

 *

 * Authors: Phil Blundell <Philip.Blundell@pobox.com>

 *          Carsten Gross <carsten@sol.wohnheim.uni-ulm.de>

 *          Jose Renau <renau@acm.org>

 *          Tim Waugh <tim@cyberelk.demon.co.uk> (largely rewritten)

 *

 * This file is responsible for IEEE 1284 negotiation, and for handing

 * read/write requests to low-level drivers.

 *

 * Any part of this program may be used in documents licensed under

 * the GNU Free Documentation License, Version 1.1 or any later version

 * published by the Free Software Foundation.

 *

 * Various hacks, Fred Barnes <frmb2@ukc.ac.uk>, 04/2000

 */

#include <linux/config.h>

#include <linux/threads.h>

#include <linux/parport.h>

#include <linux/delay.h>

#include <linux/kernel.h>

#include <linux/interrupt.h>

#undef DEBUG /* undef me for production */

#ifdef CONFIG_LP_CONSOLE

#undef DEBUG /* Don't want a garbled console */

#endif

#ifdef DEBUG

#define DPRINTK(stuff...) printk (stuff)

#else

#define DPRINTK(stuff...)

#endif

/* Make parport_wait_peripheral wake up.

 * It will be useful to call this from an interrupt handler. */

void parport_ieee1284_wakeup (struct parport *port)

{

        up (&port->physport->ieee1284.irq);

}

static struct parport *port_from_cookie[PARPORT_MAX];

static void timeout_waiting_on_port (unsigned long cookie)

{

        parport_ieee1284_wakeup (port_from_cookie[cookie % PARPORT_MAX]);

}

/**

 *      parport_wait_event - wait for an event on a parallel port

 *      @port: port to wait on

 *      @timeout: time to wait (in jiffies)

 *

 *      This function waits for up to @timeout jiffies for an

 *      interrupt to occur on a parallel port.  If the port timeout is

 *      set to zero, it returns immediately.

 *

 *      If an interrupt occurs before the timeout period elapses, this

 *      function returns one immediately.  If it times out, it returns

 *      a value greater than zero.  An error code less than zero

 *      indicates an error (most likely a pending signal), and the

 *      calling code should finish what it's doing as soon as it can.

 */

int parport_wait_event (struct parport *port, signed long timeout)

{

        int ret;

        struct timer_list timer;

        if (!port->physport->cad->timeout)

                /* Zero timeout is special, and we can't down() the

                   semaphore. */

                return 1;

        init_timer (&timer);

        timer.expires = jiffies + timeout;

        timer.function = timeout_waiting_on_port;

        port_from_cookie[port->number % PARPORT_MAX] = port;

        timer.data = port->number;

        add_timer (&timer);

        ret = down_interruptible (&port->physport->ieee1284.irq);

        if (!del_timer (&timer) && !ret)

                /* Timed out. */

                ret = 1;

        return ret;

}

/**

 *      parport_poll_peripheral - poll status lines

 *      @port: port to watch

 *      @mask: status lines to watch

 *      @result: desired values of chosen status lines

 *      @usec: timeout

 *

 *      This function busy-waits until the masked status lines have

 *      the desired values, or until the timeout period elapses.  The

 *      @mask and @result parameters are bitmasks, with the bits

 *      defined by the constants in parport.h: %PARPORT_STATUS_BUSY,

 *      and so on.

 *

 *      This function does not call schedule(); instead it busy-waits

 *      using udelay().  It currently has a resolution of 5usec.

 *

 *      If the status lines take on the desired values before the

 *      timeout period elapses, parport_poll_peripheral() returns zero

 *      immediately.  A zero return value greater than zero indicates

 *      a timeout.  An error code (less than zero) indicates an error,

 *      most likely a signal that arrived, and the caller should

 *      finish what it is doing as soon as possible.

*/

int parport_poll_peripheral(struct parport *port,

                            unsigned char mask,

                            unsigned char result,

                            int usec)

{

        /* Zero return code is success, >0 is timeout. */

        int count = usec / 5 + 2;

        int i;

        unsigned char status;

        for (i = 0; i < count; i++) {

                status = parport_read_status (port);

                if ((status & mask) == result)

                        return 0;

                if (signal_pending (current))

                        return -EINTR;

                if (current->need_resched)

                        break;

                if (i >= 2)

                        udelay (5);

        }

        return 1;

}

/**

 *      parport_wait_peripheral - wait for status lines to change in 35ms

 *      @port: port to watch

 *      @mask: status lines to watch

 *      @result: desired values of chosen status lines

 *

 *      This function waits until the masked status lines have the

 *      desired values, or until 35ms have elapsed (see IEEE 1284-1994

 *      page 24 to 25 for why this value in particular is hardcoded).

 *      The @mask and @result parameters are bitmasks, with the bits

 *      defined by the constants in parport.h: %PARPORT_STATUS_BUSY,

 *      and so on.

 *

 *      The port is polled quickly to start off with, in anticipation

 *      of a fast response from the peripheral.  This fast polling

 *      time is configurable (using /proc), and defaults to 500usec.

 *      If the timeout for this port (see parport_set_timeout()) is

 *      zero, the fast polling time is 35ms, and this function does

 *      not call schedule().

 *

 *      If the timeout for this port is non-zero, after the fast

 *      polling fails it uses parport_wait_event() to wait for up to

 *      10ms, waking up if an interrupt occurs.

 */

int parport_wait_peripheral(struct parport *port,

                            unsigned char mask,

                            unsigned char result)

{

        int ret;

        int usec;

        long deadline;

        unsigned char status;

        usec = port->physport->spintime; /* usecs of fast polling */

        if (!port->physport->cad->timeout)

                /* A zero timeout is "special": busy wait for the

                   entire 35ms. */

                usec = 35000;

        /* Fast polling.

         *

         * This should be adjustable.

         * How about making a note (in the device structure) of how long

         * it takes, so we know for next time?

         */

        ret = parport_poll_peripheral (port, mask, result, usec);

        if (ret != 1)

                return ret;

        if (!port->physport->cad->timeout)

                /* We may be in an interrupt handler, so we can't poll

                 * slowly anyway. */

                return 1;

        /* 40ms of slow polling. */

        deadline = jiffies + (HZ + 24) / 25;

        while (time_before (jiffies, deadline)) {

                int ret;

                if (signal_pending (current))

                        return -EINTR;

                /* Wait for 10ms (or until an interrupt occurs if

                 * the handler is set) */

                if ((ret = parport_wait_event (port, (HZ + 99) / 100)) < 0)

                        return ret;

                status = parport_read_status (port);

                if ((status & mask) == result)

                        return 0;

                if (!ret) {

                        /* parport_wait_event didn't time out, but the

                         * peripheral wasn't actually ready either.

                         * Wait for another 10ms. */

                        __set_current_state (TASK_INTERRUPTIBLE);

                        schedule_timeout ((HZ+ 99) / 100);

                }

        }

        return 1;

}

#ifdef CONFIG_PARPORT_1284

/* Terminate a negotiated mode. */

static void parport_ieee1284_terminate (struct parport *port)

{

        int r;

        port = port->physport;

        /* EPP terminates differently. */

        switch (port->ieee1284.mode) {

        case IEEE1284_MODE_EPP:

        case IEEE1284_MODE_EPPSL:

        case IEEE1284_MODE_EPPSWE:

                /* Terminate from EPP mode. */

                /* Event 68: Set nInit low */

                parport_frob_control (port, PARPORT_CONTROL_INIT, 0);

                udelay (50);

                /* Event 69: Set nInit high, nSelectIn low */

                parport_frob_control (port,

                                      PARPORT_CONTROL_SELECT

                                      | PARPORT_CONTROL_INIT,

                                      PARPORT_CONTROL_SELECT

                                      | PARPORT_CONTROL_INIT);

                break;

        case IEEE1284_MODE_ECP:

        case IEEE1284_MODE_ECPRLE:

        case IEEE1284_MODE_ECPSWE:

                /* In ECP we can only terminate from fwd idle phase. */

                if (port->ieee1284.phase != IEEE1284_PH_FWD_IDLE) {

                        /* Event 47: Set nInit high */

                        parport_frob_control (port,

                                              PARPORT_CONTROL_INIT

                                              | PARPORT_CONTROL_AUTOFD,

                                              PARPORT_CONTROL_INIT

                                              | PARPORT_CONTROL_AUTOFD);

                        /* Event 49: PError goes high */

                        r = parport_wait_peripheral (port,

                                                     PARPORT_STATUS_PAPEROUT,

                                                     PARPORT_STATUS_PAPEROUT);

                        if (r)

                                DPRINTK (KERN_INFO "%s: Timeout at event 49\n",

                                         port->name);

                        parport_data_forward (port);

                        DPRINTK (KERN_DEBUG "%s: ECP direction: forward\n",

                                 port->name);

                        port->ieee1284.phase = IEEE1284_PH_FWD_IDLE;

                }

                /* fall-though.. */

        default:

                /* Terminate from all other modes. */

                /* Event 22: Set nSelectIn low, nAutoFd high */

                parport_frob_control (port,

                                      PARPORT_CONTROL_SELECT

                                      | PARPORT_CONTROL_AUTOFD,

                                      PARPORT_CONTROL_SELECT);

                /* Event 24: nAck goes low */

                r = parport_wait_peripheral (port, PARPORT_STATUS_ACK, 0);

                if (r)

                        DPRINTK (KERN_INFO "%s: Timeout at event 24\n",

                                 port->name);

                /* Event 25: Set nAutoFd low */

                parport_frob_control (port,

                                      PARPORT_CONTROL_AUTOFD,

                                      PARPORT_CONTROL_AUTOFD);

                /* Event 27: nAck goes high */

                r = parport_wait_peripheral (port,

                                             PARPORT_STATUS_ACK,

                                             PARPORT_STATUS_ACK);

                if (r)

                        DPRINTK (KERN_INFO "%s: Timeout at event 27\n",

                                 port->name);

                /* Event 29: Set nAutoFd high */

                parport_frob_control (port, PARPORT_CONTROL_AUTOFD, 0);

        }

        port->ieee1284.mode = IEEE1284_MODE_COMPAT;

        port->ieee1284.phase = IEEE1284_PH_FWD_IDLE;

        DPRINTK (KERN_DEBUG "%s: In compatibility (forward idle) mode\n",

                 port->name);

}

#endif /* IEEE1284 support */

/**

 *      parport_negotiate - negotiate an IEEE 1284 mode

 *      @port: port to use

 *      @mode: mode to negotiate to

 *

 *      Use this to negotiate to a particular IEEE 1284 transfer mode.

 *      The @mode parameter should be one of the constants in

 *      parport.h starting %IEEE1284_MODE_xxx.

 *

 *      The return value is 0 if the peripheral has accepted the

 *      negotiation to the mode specified, -1 if the peripheral is not

 *      IEEE 1284 compliant (or not present), or 1 if the peripheral

 *      has rejected the negotiation.

 */

int parport_negotiate (struct parport *port, int mode)

{

#ifndef CONFIG_PARPORT_1284

        if (mode == IEEE1284_MODE_COMPAT)

                return 0;

        printk (KERN_ERR "parport: IEEE1284 not supported in this kernel\n");

        return -1;

#else

        int m = mode & ~IEEE1284_ADDR;

        int r;

        unsigned char xflag;

        port = port->physport;

        /* Is there anything to do? */

        if (port->ieee1284.mode == mode)

                return 0;

        /* Is the difference just an address-or-not bit? */

        if ((port->ieee1284.mode & ~IEEE1284_ADDR) == (mode & ~IEEE1284_ADDR)){

                port->ieee1284.mode = mode;

                return 0;

        }

        /* Go to compability forward idle mode */

        if (port->ieee1284.mode != IEEE1284_MODE_COMPAT)

                parport_ieee1284_terminate (port);

        if (mode == IEEE1284_MODE_COMPAT)

                /* Compatibility mode: no negotiation. */

                return 0;

        switch (mode) {

        case IEEE1284_MODE_ECPSWE:

                m = IEEE1284_MODE_ECP;

                break;

        case IEEE1284_MODE_EPPSL:

        case IEEE1284_MODE_EPPSWE:

                m = IEEE1284_MODE_EPP;

                break;

        case IEEE1284_MODE_BECP:

                return -ENOSYS; /* FIXME (implement BECP) */

        }

        if (mode & IEEE1284_EXT_LINK)

                m = 1<<7; /* request extensibility link */

        port->ieee1284.phase = IEEE1284_PH_NEGOTIATION;

        /* Start off with nStrobe and nAutoFd high, and nSelectIn low */

        parport_frob_control (port,

                              PARPORT_CONTROL_STROBE

                              | PARPORT_CONTROL_AUTOFD

                              | PARPORT_CONTROL_SELECT,

                              PARPORT_CONTROL_SELECT);

        udelay(1);

        /* Event 0: Set data */

        parport_data_forward (port);

        parport_write_data (port, m);

        udelay (400); /* Shouldn't need to wait this long. */

        /* Event 1: Set nSelectIn high, nAutoFd low */

        parport_frob_control (port,

                              PARPORT_CONTROL_SELECT

                              | PARPORT_CONTROL_AUTOFD,

                              PARPORT_CONTROL_AUTOFD);

        /* Event 2: PError, Select, nFault go high, nAck goes low */

        if (parport_wait_peripheral (port,

                                     PARPORT_STATUS_ERROR

                                     | PARPORT_STATUS_SELECT

                                     | PARPORT_STATUS_PAPEROUT

                                     | PARPORT_STATUS_ACK,

                                     PARPORT_STATUS_ERROR

                                     | PARPORT_STATUS_SELECT

                                     | PARPORT_STATUS_PAPEROUT)) {

                /* Timeout */

                parport_frob_control (port,

                                      PARPORT_CONTROL_SELECT

                                      | PARPORT_CONTROL_AUTOFD,

                                      PARPORT_CONTROL_SELECT);

                DPRINTK (KERN_DEBUG

                         "%s: Peripheral not IEEE1284 compliant (0x%02X)\n",

                         port->name, parport_read_status (port));

                port->ieee1284.phase = IEEE1284_PH_FWD_IDLE;

                return -1; /* Not IEEE1284 compliant */

        }

        /* Event 3: Set nStrobe low */

        parport_frob_control (port,

                              PARPORT_CONTROL_STROBE,

                              PARPORT_CONTROL_STROBE);

        /* Event 4: Set nStrobe and nAutoFd high */

        udelay (5);

        parport_frob_control (port,

                              PARPORT_CONTROL_STROBE

                              | PARPORT_CONTROL_AUTOFD,

                              0);

        /* Event 6: nAck goes high */

        if (parport_wait_peripheral (port,

                                     PARPORT_STATUS_ACK,

                                     PARPORT_STATUS_ACK)) {

                /* This shouldn't really happen with a compliant device. */

                DPRINTK (KERN_DEBUG

                         "%s: Mode 0x%02x not supported? (0x%02x)\n",

                         port->name, mode, port->ops->read_status (port));

                parport_ieee1284_terminate (port);

                return 1;

        }

        xflag = parport_read_status (port) & PARPORT_STATUS_SELECT;

        /* xflag should be high for all modes other than nibble (0). */

        if (mode && !xflag) {

                /* Mode not supported. */

                DPRINTK (KERN_DEBUG "%s: Mode 0x%02x rejected by peripheral\n",

                         port->name, mode);

                parport_ieee1284_terminate (port);

                return 1;

        }

        /* More to do if we've requested extensibility link. */

        if (mode & IEEE1284_EXT_LINK) {

                m = mode & 0x7f;

                udelay (1);

                parport_write_data (port, m);

                udelay (1);

                /* Event 51: Set nStrobe low */

                parport_frob_control (port,

                                      PARPORT_CONTROL_STROBE,

                                      PARPORT_CONTROL_STROBE);

                /* Event 52: nAck goes low */

                if (parport_wait_peripheral (port, PARPORT_STATUS_ACK, 0)) {

                        /* This peripheral is _very_ slow. */

                        DPRINTK (KERN_DEBUG

                                 "%s: Event 52 didn't happen\n",

                                 port->name);

                        parport_ieee1284_terminate (port);

                        return 1;

                }

                /* Event 53: Set nStrobe high */

                parport_frob_control (port,

                                      PARPORT_CONTROL_STROBE,

                                      0);

                /* Event 55: nAck goes high */

                if (parport_wait_peripheral (port,

                                             PARPORT_STATUS_ACK,

                                             PARPORT_STATUS_ACK)) {

                        /* This shouldn't really happen with a compliant

                         * device. */

                        DPRINTK (KERN_DEBUG

                                 "%s: Mode 0x%02x not supported? (0x%02x)\n",

                                 port->name, mode,

                                 port->ops->read_status (port));

                        parport_ieee1284_terminate (port);

                        return 1;

                }

                /* Event 54: Peripheral sets XFlag to reflect support */

                xflag = parport_read_status (port) & PARPORT_STATUS_SELECT;

                /* xflag should be high. */

                if (!xflag) {

                        /* Extended mode not supported. */

                        DPRINTK (KERN_DEBUG "%s: Extended mode 0x%02x not "

                                 "supported\n", port->name, mode);

                        parport_ieee1284_terminate (port);

                        return 1;

                }

                /* Any further setup is left to the caller. */

        }

        /* Mode is supported */

        DPRINTK (KERN_DEBUG "%s: In mode 0x%02x\n", port->name, mode);

        port->ieee1284.mode = mode;

        /* But ECP is special */

        if (!(mode & IEEE1284_EXT_LINK) && (m & IEEE1284_MODE_ECP)) {

                port->ieee1284.phase = IEEE1284_PH_ECP_SETUP;

                /* Event 30: Set nAutoFd low */

                parport_frob_control (port,

                                      PARPORT_CONTROL_AUTOFD,

                                      PARPORT_CONTROL_AUTOFD);

                /* Event 31: PError goes high. */

                r = parport_wait_peripheral (port,

                                             PARPORT_STATUS_PAPEROUT,

                                             PARPORT_STATUS_PAPEROUT);

                if (r) {

                        DPRINTK (KERN_INFO "%s: Timeout at event 31\n",

                                port->name);

                }

                port->ieee1284.phase = IEEE1284_PH_FWD_IDLE;

                DPRINTK (KERN_DEBUG "%s: ECP direction: forward\n",

                         port->name);

        } else switch (mode) {

        case IEEE1284_MODE_NIBBLE:

        case IEEE1284_MODE_BYTE:

                port->ieee1284.phase = IEEE1284_PH_REV_IDLE;

                break;

        default:

                port->ieee1284.phase = IEEE1284_PH_FWD_IDLE;

        }

        return 0;

#endif /* IEEE1284 support */

}

/* Acknowledge that the peripheral has data available.

 * Events 18-20, in order to get from Reverse Idle phase

 * to Host Busy Data Available.

 * This will most likely be called from an interrupt.

 * Returns zero if data was available.

 */

#ifdef CONFIG_PARPORT_1284

static int parport_ieee1284_ack_data_avail (struct parport *port)

{

        if (parport_read_status (port) & PARPORT_STATUS_ERROR)

                /* Event 18 didn't happen. */

                return -1;

        /* Event 20: nAutoFd goes high. */

        port->ops->frob_control (port, PARPORT_CONTROL_AUTOFD, 0);

        port->ieee1284.phase = IEEE1284_PH_HBUSY_DAVAIL;

        return 0;

}

#endif /* IEEE1284 support */

/* Handle an interrupt. */

void parport_ieee1284_interrupt (int which, void *handle, struct pt_regs *regs)

{

        struct parport *port = handle;

        parport_ieee1284_wakeup (port);

#ifdef CONFIG_PARPORT_1284

        if (port->ieee1284.phase == IEEE1284_PH_REV_IDLE) {

                /* An interrupt in this phase means that data

                 * is now available. */

                DPRINTK (KERN_DEBUG "%s: Data available\n", port->name);

                parport_ieee1284_ack_data_avail (port);

        }

#endif /* IEEE1284 support */

}

/**

 *      parport_write - write a block of data to a parallel port

 *      @port: port to write to

 *      @buffer: data buffer (in kernel space)

 *      @len: number of bytes of data to transfer

 *

 *      This will write up to @len bytes of @buffer to the port

 *      specified, using the IEEE 1284 transfer mode most recently

 *      negotiated to (using parport_negotiate()), as long as that

 *      mode supports forward transfers (host to peripheral).

 *

 *      It is the caller's responsibility to ensure that the first

 *      @len bytes of @buffer are valid.

 *

 *      This function returns the number of bytes transferred (if zero

 *      or positive), or else an error code.

 */

ssize_t parport_write (struct parport *port, const void *buffer, size_t len)

{

#ifndef CONFIG_PARPORT_1284

        return port->ops->compat_write_data (port, buffer, len, 0);

#else

        ssize_t retval;

        int mode = port->ieee1284.mode;

        int addr = mode & IEEE1284_ADDR;

        size_t (*fn) (struct parport *, const void *, size_t, int);

        /* Ignore the device-ID-request bit and the address bit. */

        mode &= ~(IEEE1284_DEVICEID | IEEE1284_ADDR);

        /* Use the mode we're in. */

        switch (mode) {

        case IEEE1284_MODE_NIBBLE:

        case IEEE1284_MODE_BYTE:

                parport_negotiate (port, IEEE1284_MODE_COMPAT);

        case IEEE1284_MODE_COMPAT:

                DPRINTK (KERN_DEBUG "%s: Using compatibility mode\n",

                         port->name);

                fn = port->ops->compat_write_data;

                break;

        case IEEE1284_MODE_EPP:

                DPRINTK (KERN_DEBUG "%s: Using EPP mode\n", port->name);

                if (addr) {

                        fn = port->ops->epp_write_addr;

                } else {

                        fn = port->ops->epp_write_data;

                }

                break;

        case IEEE1284_MODE_EPPSWE:

                DPRINTK (KERN_DEBUG "%s: Using software-emulated EPP mode\n",

                        port->name);

                if (addr) {

                        fn = parport_ieee1284_epp_write_addr;

                } else {

                        fn = parport_ieee1284_epp_write_data;

                }

                break;

        case IEEE1284_MODE_ECP:

        case IEEE1284_MODE_ECPRLE:

                DPRINTK (KERN_DEBUG "%s: Using ECP mode\n", port->name);

                if (addr) {

                        fn = port->ops->ecp_write_addr;

                } else {

                        fn = port->ops->ecp_write_data;

                }

                break;

        case IEEE1284_MODE_ECPSWE:

                DPRINTK (KERN_DEBUG "%s: Using software-emulated ECP mode\n",

                         port->name);

                /* The caller has specified that it must be emulated,

                 * even if we have ECP hardware! */

                if (addr) {

                        fn = parport_ieee1284_ecp_write_addr;

                } else {

                        fn = parport_ieee1284_ecp_write_data;

                }

                break;

        default:

                DPRINTK (KERN_DEBUG "%s: Unknown mode 0x%02x\n", port->name,

                        port->ieee1284.mode);

                return -ENOSYS;

        }

        retval = (*fn) (port, buffer, len, 0);

        DPRINTK (KERN_DEBUG "%s: wrote %d/%d bytes\n", port->name, retval, len);

        return retval;

#endif /* IEEE1284 support */

}

/**

 *      parport_read - read a block of data from a parallel port

 *      @port: port to read from

 *      @buffer: data buffer (in kernel space)

 *      @len: number of bytes of data to transfer

 *

 *      This will read up to @len bytes of @buffer to the port

 *      specified, using the IEEE 1284 transfer mode most recently

 *      negotiated to (using parport_negotiate()), as long as that

 *      mode supports reverse transfers (peripheral to host).

 *

 *      It is the caller's responsibility to ensure that the first

 *      @len bytes of @buffer are available to write to.

 *

 *      This function returns the number of bytes transferred (if zero

 *      or positive), or else an error code.

 */

ssize_t parport_read (struct parport *port, void *buffer, size_t len)

{

#ifndef CONFIG_PARPORT_1284

        printk (KERN_ERR "parport: IEEE1284 not supported in this kernel\n");

        return -ENODEV;

#else

        int mode = port->physport->ieee1284.mode;

        int addr = mode & IEEE1284_ADDR;

        size_t (*fn) (struct parport *, void *, size_t, int);

        /* Ignore the device-ID-request bit and the address bit. */

        mode &= ~(IEEE1284_DEVICEID | IEEE1284_ADDR);

        /* Use the mode we're in. */

        switch (mode) {

        case IEEE1284_MODE_COMPAT:

                /* if we can tri-state use BYTE mode instead of NIBBLE mode,

                 * if that fails, revert to NIBBLE mode -- ought to store somewhere

                 * the device's ability to do BYTE mode reverse transfers, so we don't

                 * end up needlessly calling negotiate(BYTE) repeately..  (fb)

                 */

                if ((port->physport->modes & PARPORT_MODE_TRISTATE) &&

                    !parport_negotiate (port, IEEE1284_MODE_BYTE)) {

                        /* got into BYTE mode OK */

                        DPRINTK (KERN_DEBUG "%s: Using byte mode\n", port->name);

                        fn = port->ops->byte_read_data;

                        break;

                }

                if (parport_negotiate (port, IEEE1284_MODE_NIBBLE)) {

                        return -EIO;

                }

                /* fall through to NIBBLE */

        case IEEE1284_MODE_NIBBLE:

                DPRINTK (KERN_DEBUG "%s: Using nibble mode\n", port->name);

                fn = port->ops->nibble_read_data;

                break;