drivers/macintosh/via-macii.c - android_kernel_htc_msm8960 - Gitiles

 /*
  * Device driver for the via ADB on (many) Mac II-class machines
  *
  * Based on the original ADB keyboard handler Copyright (c) 1997 Alan Cox
  * Also derived from code Copyright (C) 1996 Paul Mackerras.
  *
  * With various updates provided over the years by Michael Schmitz,
  * Guideo Koerber and others.
  *
  * Rewrite for Unified ADB by Joshua M. Thompson (funaho@jurai.org)
  *
  * 1999-08-02 (jmt) - Initial rewrite for Unified ADB.
  * 2000-03-29 Tony Mantler <tonym@mac.linux-m68k.org>
  * 				- Big overhaul, should actually work now.
  */

 #include <stdarg.h>
 #include <linux/types.h>
 #include <linux/errno.h>
 #include <linux/kernel.h>
 #include <linux/delay.h>
 #include <linux/sched.h>
 #include <linux/adb.h>
 #include <linux/interrupt.h>
 #include <linux/init.h>
 #include <asm/macintosh.h>
 #include <asm/macints.h>
 #include <asm/machw.h>
 #include <asm/mac_via.h>
 #include <asm/io.h>
 #include <asm/system.h>

 static volatile unsigned char *via;

 /* VIA registers - spaced 0x200 bytes apart */
 #define RS		0x200		/* skip between registers */
 #define B		0		/* B-side data */
 #define A		RS		/* A-side data */
 #define DIRB		(2*RS)		/* B-side direction (1=output) */
 #define DIRA		(3*RS)		/* A-side direction (1=output) */
 #define T1CL		(4*RS)		/* Timer 1 ctr/latch (low 8 bits) */
 #define T1CH		(5*RS)		/* Timer 1 counter (high 8 bits) */
 #define T1LL		(6*RS)		/* Timer 1 latch (low 8 bits) */
 #define T1LH		(7*RS)		/* Timer 1 latch (high 8 bits) */
 #define T2CL		(8*RS)		/* Timer 2 ctr/latch (low 8 bits) */
 #define T2CH		(9*RS)		/* Timer 2 counter (high 8 bits) */
 #define SR		(10*RS)		/* Shift register */
 #define ACR		(11*RS)		/* Auxiliary control register */
 #define PCR		(12*RS)		/* Peripheral control register */
 #define IFR		(13*RS)		/* Interrupt flag register */
 #define IER		(14*RS)		/* Interrupt enable register */
 #define ANH		(15*RS)		/* A-side data, no handshake */

 /* Bits in B data register: all active low */
 #define TREQ		0x08		/* Transfer request (input) */
 #define TACK		0x10		/* Transfer acknowledge (output) */
 #define TIP		0x20		/* Transfer in progress (output) */
 #define ST_MASK		0x30		/* mask for selecting ADB state bits */

 /* Bits in ACR */
 #define SR_CTRL		0x1c		/* Shift register control bits */
 #define SR_EXT		0x0c		/* Shift on external clock */
 #define SR_OUT		0x10		/* Shift out if 1 */

 /* Bits in IFR and IER */
 #define IER_SET		0x80		/* set bits in IER */
 #define IER_CLR		0		/* clear bits in IER */
 #define SR_INT		0x04		/* Shift register full/empty */
 #define SR_DATA		0x08		/* Shift register data */
 #define SR_CLOCK	0x10		/* Shift register clock */

 /* ADB transaction states according to GMHW */
 #define ST_CMD		0x00		/* ADB state: command byte */
 #define ST_EVEN		0x10		/* ADB state: even data byte */
 #define ST_ODD		0x20		/* ADB state: odd data byte */
 #define ST_IDLE		0x30		/* ADB state: idle, nothing to send */

 static int  macii_init_via(void);
 static void macii_start(void);
 static irqreturn_t macii_interrupt(int irq, void *arg, struct pt_regs *regs);
 static void macii_retransmit(int);
 static void macii_queue_poll(void);

 static int macii_probe(void);
 static int macii_init(void);
 static int macii_send_request(struct adb_request *req, int sync);
 static int macii_write(struct adb_request *req);
 static int macii_autopoll(int devs);
 static void macii_poll(void);
 static int macii_reset_bus(void);

 struct adb_driver via_macii_driver = {
 	"Mac II",
 	macii_probe,
 	macii_init,
 	macii_send_request,
 	macii_autopoll,
 	macii_poll,
 	macii_reset_bus
 };

 static enum macii_state {
 	idle,
 	sending,
 	reading,
 	read_done,
 	awaiting_reply
 } macii_state;

 static int need_poll    = 0;
 static int command_byte = 0;
 static int last_reply   = 0;
 static int last_active  = 0;

 static struct adb_request *current_req;
 static struct adb_request *last_req;
 static struct adb_request *retry_req;
 static unsigned char reply_buf[16];
 static unsigned char *reply_ptr;
 static int reply_len;
 static int reading_reply;
 static int data_index;
 static int first_byte;
 static int prefix_len;
 static int status = ST_IDLE|TREQ;
 static int last_status;
 static int driver_running = 0;

 /* debug level 10 required for ADB logging (should be && debug_adb, ideally) */

 /* Check for MacII style ADB */
 static int macii_probe(void)
 {
 	if (macintosh_config->adb_type != MAC_ADB_II) return -ENODEV;

 	via = via1;

 	printk("adb: Mac II ADB Driver v1.0 for Unified ADB\n");
 	return 0;
 }

 /* Initialize the driver */
 int macii_init(void)
 {
 	unsigned long flags;
 	int err;

 	local_irq_save(flags);

 	err = macii_init_via();
 	if (err) return err;

 	err = request_irq(IRQ_MAC_ADB, macii_interrupt, IRQ_FLG_LOCK, "ADB",
 			  macii_interrupt);
 	if (err) return err;

 	macii_state = idle;
 	local_irq_restore(flags);
 	return 0;
 }

 /* initialize the hardware */
 static int macii_init_via(void)
 {
 	unsigned char x;

 	/* Set the lines up. We want TREQ as input TACK|TIP as output */
 	via[DIRB] = (via[DIRB] | TACK | TIP) & ~TREQ;

 	/* Set up state: idle */
 	via[B] |= ST_IDLE;
 	last_status = via[B] & (ST_MASK|TREQ);

 	/* Shift register on input */
 	via[ACR] = (via[ACR] & ~SR_CTRL) | SR_EXT;

 	/* Wipe any pending data and int */
 	x = via[SR];

 	return 0;
 }

 /* Send an ADB poll (Talk Register 0 command, tagged on the front of the request queue) */
 static void macii_queue_poll(void)
 {
 	static int device = 0;
 	static int in_poll=0;
 	static struct adb_request req;
 	unsigned long flags;

 	if (in_poll) printk("macii_queue_poll: double poll!\n");

 	in_poll++;
 	if (++device > 15) device = 1;

 	adb_request(&req, NULL, ADBREQ_REPLY|ADBREQ_NOSEND, 1,
 		    ADB_READREG(device, 0));

 	local_irq_save(flags);

 	req.next = current_req;
 	current_req = &req;

 	local_irq_restore(flags);
 	macii_start();
 	in_poll--;
 }

 /* Send an ADB retransmit (Talk, appended to the request queue) */
 static void macii_retransmit(int device)
 {
 	static int in_retransmit = 0;
 	static struct adb_request rt;
 	unsigned long flags;

 	if (in_retransmit) printk("macii_retransmit: double retransmit!\n");

 	in_retransmit++;

 	adb_request(&rt, NULL, ADBREQ_REPLY|ADBREQ_NOSEND, 1,
 		    ADB_READREG(device, 0));

 	local_irq_save(flags);

 	if (current_req != NULL) {
 		last_req->next = &rt;
 		last_req = &rt;
 	} else {
 		current_req = &rt;
 		last_req = &rt;
 	}

 	if (macii_state == idle) macii_start();

 	local_irq_restore(flags);
 	in_retransmit--;
 }

 /* Send an ADB request; if sync, poll out the reply 'till it's done */
 static int macii_send_request(struct adb_request *req, int sync)
 {
 	int i;

 	i = macii_write(req);
 	if (i) return i;

 	if (sync) {
 		while (!req->complete) macii_poll();
 	}
 	return 0;
 }

 /* Send an ADB request */
 static int macii_write(struct adb_request *req)
 {
 	unsigned long flags;

 	if (req->nbytes < 2 || req->data[0] != ADB_PACKET || req->nbytes > 15) {
 		req->complete = 1;
 		return -EINVAL;
 	}

 	req->next = 0;
 	req->sent = 0;
 	req->complete = 0;
 	req->reply_len = 0;

 	local_irq_save(flags);

 	if (current_req != NULL) {
 		last_req->next = req;
 		last_req = req;
 	} else {
 		current_req = req;
 		last_req = req;
 		if (macii_state == idle) macii_start();
 	}

 	local_irq_restore(flags);
 	return 0;
 }

 /* Start auto-polling */
 static int macii_autopoll(int devs)
 {
 	/* Just ping a random default address */
 	if (!(current_req || retry_req))
 		macii_retransmit( (last_active < 16 && last_active > 0) ? last_active : 3);
 	return 0;
 }

 /* Prod the chip without interrupts */
 static void macii_poll(void)
 {
 	unsigned long flags;

 	local_irq_save(flags);
 	if (via[IFR] & SR_INT) macii_interrupt(0, 0, 0);
 	local_irq_restore(flags);
 }

 /* Reset the bus */
 static int macii_reset_bus(void)
 {
 	static struct adb_request req;

 	/* Command = 0, Address = ignored */
 	adb_request(&req, NULL, 0, 1, ADB_BUSRESET);

 	return 0;
 }

 /* Start sending ADB packet */
 static void macii_start(void)
 {
 	unsigned long flags;
 	struct adb_request *req;

 	req = current_req;
 	if (!req) return;

 	/* assert macii_state == idle */
 	if (macii_state != idle) {
 		printk("macii_start: called while driver busy (%p %x %x)!\n",
 			req, macii_state, (uint) via1[B] & (ST_MASK|TREQ));
 		return;
 	}

 	local_irq_save(flags);

 	/*
 	 * IRQ signaled ?? (means ADB controller wants to send, or might
 	 * be end of packet if we were reading)
 	 */
 #if 0 /* FIXME: This is broke broke broke, for some reason */
 	if ((via[B] & TREQ) == 0) {
 		printk("macii_start: weird poll stuff. huh?\n");
 		/*
 		 *	FIXME - we need to restart this on a timer
 		 *	or a collision at boot hangs us.
 		 *	Never set macii_state to idle here, or macii_start
 		 *	won't be called again from send_request!
 		 *	(need to re-check other cases ...)
 		 */
 		/*
 		 * if the interrupt handler set the need_poll
 		 * flag, it's hopefully a SRQ poll or re-Talk
 		 * so we try to send here anyway
 		 */
 		if (!need_poll) {
 			if (console_loglevel == 10)
 				printk("macii_start: device busy - retry %p state %d status %x!\n",
 					req, macii_state,
 					(uint) via[B] & (ST_MASK|TREQ));
 			retry_req = req;
 			/* set ADB status here ? */
 			local_irq_restore(flags);
 			return;
 		} else {
 			need_poll = 0;
 		}
 	}
 #endif
 	/*
 	 * Another retry pending? (sanity check)
 	 */
 	if (retry_req) {
 		retry_req = NULL;
 	}

 	/* Now send it. Be careful though, that first byte of the request */
 	/* is actually ADB_PACKET; the real data begins at index 1!	  */

 	/* store command byte */
 	command_byte = req->data[1];
 	/* Output mode */
 	via[ACR] |= SR_OUT;
 	/* Load data */
 	via[SR] = req->data[1];
 	/* set ADB state to 'command' */
 	via[B] = (via[B] & ~ST_MASK) | ST_CMD;

 	macii_state = sending;
 	data_index = 2;

 	local_irq_restore(flags);
 }

 /*
  * The notorious ADB interrupt handler - does all of the protocol handling,
  * except for starting new send operations. Relies heavily on the ADB
  * controller sending and receiving data, thereby generating SR interrupts
  * for us. This means there has to be always activity on the ADB bus, otherwise
  * the whole process dies and has to be re-kicked by sending TALK requests ...
  * CUDA-based Macs seem to solve this with the autopoll option, for MacII-type
  * ADB the problem isn't solved yet (retransmit of the latest active TALK seems
  * a good choice; either on timeout or on a timer interrupt).
  *
  * The basic ADB state machine was left unchanged from the original MacII code
  * by Alan Cox, which was based on the CUDA driver for PowerMac.
  * The syntax of the ADB status lines seems to be totally different on MacII,
  * though. MacII uses the states Command -> Even -> Odd -> Even ->...-> Idle for
  * sending, and Idle -> Even -> Odd -> Even ->...-> Idle for receiving. Start
  * and end of a receive packet are signaled by asserting /IRQ on the interrupt
  * line. Timeouts are signaled by a sequence of 4 0xFF, with /IRQ asserted on
  * every other byte. SRQ is probably signaled by 3 or more 0xFF tacked on the
  * end of a packet. (Thanks to Guido Koerber for eavesdropping on the ADB
  * protocol with a logic analyzer!!)
  *
  * Note: As of 21/10/97, the MacII ADB part works including timeout detection
  * and retransmit (Talk to the last active device).
  */
 static irqreturn_t macii_interrupt(int irq, void *arg, struct pt_regs *regs)
 {
 	int x, adbdir;
 	unsigned long flags;
 	struct adb_request *req;

 	last_status = status;

 	/* prevent races due to SCSI enabling ints */
 	local_irq_save(flags);

 	if (driver_running) {
 		local_irq_restore(flags);
 		return IRQ_NONE;
 	}

 	driver_running = 1;

 	status = via[B] & (ST_MASK|TREQ);
 	adbdir = via[ACR] & SR_OUT;

 	switch (macii_state) {
 		case idle:
 			x = via[SR];
 			first_byte = x;
 			/* set ADB state = even for first data byte */
 			via[B] = (via[B] & ~ST_MASK) | ST_EVEN;

 			reply_buf[0] = first_byte; /* was command_byte?? */
 			reply_ptr = reply_buf + 1;
 			reply_len = 1;
 			prefix_len = 1;
 			reading_reply = 0;

 			macii_state = reading;
 			break;

 		case awaiting_reply:
 			/* handshake etc. for II ?? */
 			x = via[SR];
 			first_byte = x;
 			/* set ADB state = even for first data byte */
 			via[B] = (via[B] & ~ST_MASK) | ST_EVEN;

 			current_req->reply[0] = first_byte;
 			reply_ptr = current_req->reply + 1;
 			reply_len = 1;
 			prefix_len = 1;
 			reading_reply = 1;

 			macii_state = reading;
 			break;

 		case sending:
 			req = current_req;
 			if (data_index >= req->nbytes) {
 				/* print an error message if a listen command has no data */
 				if (((command_byte & 0x0C) == 0x08)
 				 /* && (console_loglevel == 10) */
 				    && (data_index == 2))
 					printk("MacII ADB: listen command with no data: %x!\n",
 						command_byte);
 				/* reset to shift in */
 				via[ACR] &= ~SR_OUT;
 				x = via[SR];
 				/* set ADB state idle - might get SRQ */
 				via[B] = (via[B] & ~ST_MASK) | ST_IDLE;

 				req->sent = 1;

 				if (req->reply_expected) {
 					macii_state = awaiting_reply;
 				} else {
 					req->complete = 1;
 					current_req = req->next;
 					if (req->done) (*req->done)(req);
 					macii_state = idle;
 					if (current_req || retry_req)
 						macii_start();
 					else
 						macii_retransmit((command_byte & 0xF0) >> 4);
 				}
 			} else {
 				via[SR] = req->data[data_index++];

 				if ( (via[B] & ST_MASK) == ST_CMD ) {
 					/* just sent the command byte, set to EVEN */
 					via[B] = (via[B] & ~ST_MASK) | ST_EVEN;
 				} else {
 					/* invert state bits, toggle ODD/EVEN */
 					via[B] ^= ST_MASK;
 				}
 			}
 			break;

 		case reading:

 			/* timeout / SRQ handling for II hw */
 			if( (first_byte == 0xFF && (reply_len-prefix_len)==2
 			     && memcmp(reply_ptr-2,"\xFF\xFF",2)==0) ||
 			    ((reply_len-prefix_len)==3
 			     && memcmp(reply_ptr-3,"\xFF\xFF\xFF",3)==0))
 			{
 				/*
 				 * possible timeout (in fact, most probably a
 				 * timeout, since SRQ can't be signaled without
 				 * transfer on the bus).
 				 * The last three bytes seen were FF, together
 				 * with the starting byte (in case we started
 				 * on 'idle' or 'awaiting_reply') this probably
 				 * makes four. So this is mostl likely #5!
 				 * The timeout signal is a pattern 1 0 1 0 0..
 				 * on /INT, meaning we missed it :-(
 				 */
 				x = via[SR];
 				if (x != 0xFF) printk("MacII ADB: mistaken timeout/SRQ!\n");

 				if ((status & TREQ) == (last_status & TREQ)) {
 					/* Not a timeout. Unsolicited SRQ? weird. */
 					/* Terminate the SRQ packet and poll */
 					need_poll = 1;
 				}
 				/* There's no packet to get, so reply is blank */
 				via[B] ^= ST_MASK;
 				reply_ptr -= (reply_len-prefix_len);
 				reply_len = prefix_len;
 				macii_state = read_done;
 				break;
 			} /* end timeout / SRQ handling for II hw. */

 			if((reply_len-prefix_len)>3
 				&& memcmp(reply_ptr-3,"\xFF\xFF\xFF",3)==0)
 			{
 				/* SRQ tacked on data packet */
 				/* Terminate the packet (SRQ never ends) */
 				x = via[SR];
 				macii_state = read_done;
 				reply_len -= 3;
 				reply_ptr -= 3;
 				need_poll = 1;
 				/* need to continue; next byte not seen else */
 			} else {
 				/* Sanity check */
 				if (reply_len > 15) reply_len = 0;
 				/* read byte */
 				x = via[SR];
 				*reply_ptr = x;
 				reply_ptr++;
 				reply_len++;
 			}
 			/* The usual handshake ... */

 			/*
 			 * NetBSD hints that the next to last byte
 			 * is sent with IRQ !!
 			 * Guido found out it's the last one (0x0),
 			 * but IRQ should be asserted already.
 			 * Problem with timeout detection: First
 			 * transition to /IRQ might be second
 			 * byte of timeout packet!
 			 * Timeouts are signaled by 4x FF.
 			 */
 			if (((status & TREQ) == 0) && (x == 0x00)) { /* != 0xFF */
 				/* invert state bits, toggle ODD/EVEN */
 				via[B] ^= ST_MASK;

 				/* adjust packet length */
 				reply_len--;
 				reply_ptr--;
 				macii_state = read_done;
 			} else {
 				/* not caught: ST_CMD */
 				/* required for re-entry 'reading'! */
 				if ((status & ST_MASK) == ST_IDLE) {
 					/* (in)sanity check - set even */
 					via[B] = (via[B] & ~ST_MASK) | ST_EVEN;
 				} else {
 					/* invert state bits */
 					via[B] ^= ST_MASK;
 				}
 			}
 			break;

 		case read_done:
 			x = via[SR];
 			if (reading_reply) {
 				req = current_req;
 				req->reply_len = reply_ptr - req->reply;
 				req->complete = 1;
 				current_req = req->next;
 				if (req->done) (*req->done)(req);
 			} else {
 				adb_input(reply_buf, reply_ptr - reply_buf,
 					  regs, 0);
 			}

 			/*
 			 * remember this device ID; it's the latest we got a
 			 * reply from!
 			 */
 			last_reply = command_byte;
 			last_active = (command_byte & 0xF0) >> 4;

 			/* SRQ seen before, initiate poll now */
 			if (need_poll) {
 				macii_state = idle;
 				macii_queue_poll();
 				need_poll = 0;
 				break;
 			}

 			/* set ADB state to idle */
 			via[B] = (via[B] & ~ST_MASK) | ST_IDLE;

 			/* /IRQ seen, so the ADB controller has data for us */
 			if ((via[B] & TREQ) != 0) {
 				macii_state = reading;

 				reply_buf[0] = command_byte;
 				reply_ptr = reply_buf + 1;
 				reply_len = 1;
 				prefix_len = 1;
 				reading_reply = 0;
 			} else {
 				/* no IRQ, send next packet or wait */
 				macii_state = idle;
 				if (current_req)
 					macii_start();
 				else
 					macii_retransmit(last_active);
 			}
 			break;

 		default:
 		break;
 	}
 	/* reset mutex and interrupts */
 	driver_running = 0;
 	local_irq_restore(flags);
 	return IRQ_HANDLED;
 }
	/*
	* Device driver for the via ADB on (many) Mac II-class machines
	*
	* Based on the original ADB keyboard handler Copyright (c) 1997 Alan Cox
	* Also derived from code Copyright (C) 1996 Paul Mackerras.
	*
	* With various updates provided over the years by Michael Schmitz,
	* Guideo Koerber and others.
	*
	* Rewrite for Unified ADB by Joshua M. Thompson (funaho@jurai.org)
	*
	* 1999-08-02 (jmt) - Initial rewrite for Unified ADB.
	* 2000-03-29 Tony Mantler <tonym@mac.linux-m68k.org>
	* - Big overhaul, should actually work now.
	*/

	#include <stdarg.h>
	#include <linux/types.h>
	#include <linux/errno.h>
	#include <linux/kernel.h>
	#include <linux/delay.h>
	#include <linux/sched.h>
	#include <linux/adb.h>
	#include <linux/interrupt.h>
	#include <linux/init.h>
	#include <asm/macintosh.h>
	#include <asm/macints.h>
	#include <asm/machw.h>
	#include <asm/mac_via.h>
	#include <asm/io.h>
	#include <asm/system.h>

	static volatile unsigned char *via;

	/* VIA registers - spaced 0x200 bytes apart */
	#define RS 0x200 /* skip between registers */
	#define B 0 /* B-side data */
	#define A RS /* A-side data */
	#define DIRB (2RS) / B-side direction (1=output) */
	#define DIRA (3RS) / A-side direction (1=output) */
	#define T1CL (4RS) / Timer 1 ctr/latch (low 8 bits) */
	#define T1CH (5RS) / Timer 1 counter (high 8 bits) */
	#define T1LL (6RS) / Timer 1 latch (low 8 bits) */
	#define T1LH (7RS) / Timer 1 latch (high 8 bits) */
	#define T2CL (8RS) / Timer 2 ctr/latch (low 8 bits) */
	#define T2CH (9RS) / Timer 2 counter (high 8 bits) */
	#define SR (10RS) / Shift register */
	#define ACR (11RS) / Auxiliary control register */
	#define PCR (12RS) / Peripheral control register */
	#define IFR (13RS) / Interrupt flag register */
	#define IER (14RS) / Interrupt enable register */
	#define ANH (15RS) / A-side data, no handshake */

	/* Bits in B data register: all active low */
	#define TREQ 0x08 /* Transfer request (input) */
	#define TACK 0x10 /* Transfer acknowledge (output) */
	#define TIP 0x20 /* Transfer in progress (output) */
	#define ST_MASK 0x30 /* mask for selecting ADB state bits */

	/* Bits in ACR */
	#define SR_CTRL 0x1c /* Shift register control bits */
	#define SR_EXT 0x0c /* Shift on external clock */
	#define SR_OUT 0x10 /* Shift out if 1 */

	/* Bits in IFR and IER */
	#define IER_SET 0x80 /* set bits in IER */
	#define IER_CLR 0 /* clear bits in IER */
	#define SR_INT 0x04 /* Shift register full/empty */
	#define SR_DATA 0x08 /* Shift register data */
	#define SR_CLOCK 0x10 /* Shift register clock */

	/* ADB transaction states according to GMHW */
	#define ST_CMD 0x00 /* ADB state: command byte */
	#define ST_EVEN 0x10 /* ADB state: even data byte */
	#define ST_ODD 0x20 /* ADB state: odd data byte */
	#define ST_IDLE 0x30 /* ADB state: idle, nothing to send */

	static int macii_init_via(void);
	static void macii_start(void);
	static irqreturn_t macii_interrupt(int irq, void arg, struct pt_regs regs);
	static void macii_retransmit(int);
	static void macii_queue_poll(void);

	static int macii_probe(void);
	static int macii_init(void);
	static int macii_send_request(struct adb_request *req, int sync);
	static int macii_write(struct adb_request *req);
	static int macii_autopoll(int devs);
	static void macii_poll(void);
	static int macii_reset_bus(void);

	struct adb_driver via_macii_driver = {
	"Mac II",
	macii_probe,
	macii_init,
	macii_send_request,
	macii_autopoll,
	macii_poll,
	macii_reset_bus
	};

	static enum macii_state {
	idle,
	sending,
	reading,
	read_done,
	awaiting_reply
	} macii_state;

	static int need_poll = 0;
	static int command_byte = 0;
	static int last_reply = 0;
	static int last_active = 0;

	static struct adb_request *current_req;
	static struct adb_request *last_req;
	static struct adb_request *retry_req;
	static unsigned char reply_buf[16];
	static unsigned char *reply_ptr;
	static int reply_len;
	static int reading_reply;
	static int data_index;
	static int first_byte;
	static int prefix_len;
	static int status = ST_IDLE\|TREQ;
	static int last_status;
	static int driver_running = 0;

	/* debug level 10 required for ADB logging (should be && debug_adb, ideally) */

	/* Check for MacII style ADB */
	static int macii_probe(void)
	{
	if (macintosh_config->adb_type != MAC_ADB_II) return -ENODEV;

	via = via1;

	printk("adb: Mac II ADB Driver v1.0 for Unified ADB\n");
	return 0;
	}

	/* Initialize the driver */
	int macii_init(void)
	{
	unsigned long flags;
	int err;

	local_irq_save(flags);

	err = macii_init_via();
	if (err) return err;

	err = request_irq(IRQ_MAC_ADB, macii_interrupt, IRQ_FLG_LOCK, "ADB",
	macii_interrupt);
	if (err) return err;

	macii_state = idle;
	local_irq_restore(flags);
	return 0;
	}

	/* initialize the hardware */
	static int macii_init_via(void)
	{
	unsigned char x;

	/* Set the lines up. We want TREQ as input TACK\|TIP as output */
	via[DIRB] = (via[DIRB] \| TACK \| TIP) & ~TREQ;

	/* Set up state: idle */
	via[B] \|= ST_IDLE;
	last_status = via[B] & (ST_MASK\|TREQ);

	/* Shift register on input */
	via[ACR] = (via[ACR] & ~SR_CTRL) \| SR_EXT;

	/* Wipe any pending data and int */
	x = via[SR];

	return 0;
	}

	/* Send an ADB poll (Talk Register 0 command, tagged on the front of the request queue) */
	static void macii_queue_poll(void)
	{
	static int device = 0;
	static int in_poll=0;
	static struct adb_request req;
	unsigned long flags;

	if (in_poll) printk("macii_queue_poll: double poll!\n");

	in_poll++;
	if (++device > 15) device = 1;

	adb_request(&req, NULL, ADBREQ_REPLY\|ADBREQ_NOSEND, 1,
	ADB_READREG(device, 0));

	local_irq_save(flags);

	req.next = current_req;
	current_req = &req;

	local_irq_restore(flags);
	macii_start();
	in_poll--;
	}

	/* Send an ADB retransmit (Talk, appended to the request queue) */
	static void macii_retransmit(int device)
	{
	static int in_retransmit = 0;
	static struct adb_request rt;
	unsigned long flags;

	if (in_retransmit) printk("macii_retransmit: double retransmit!\n");

	in_retransmit++;

	adb_request(&rt, NULL, ADBREQ_REPLY\|ADBREQ_NOSEND, 1,
	ADB_READREG(device, 0));

	local_irq_save(flags);

	if (current_req != NULL) {
	last_req->next = &rt;
	last_req = &rt;
	} else {
	current_req = &rt;
	last_req = &rt;
	}

	if (macii_state == idle) macii_start();

	local_irq_restore(flags);
	in_retransmit--;
	}

	/* Send an ADB request; if sync, poll out the reply 'till it's done */
	static int macii_send_request(struct adb_request *req, int sync)
	{
	int i;

	i = macii_write(req);
	if (i) return i;

	if (sync) {
	while (!req->complete) macii_poll();
	}
	return 0;
	}

	/* Send an ADB request */
	static int macii_write(struct adb_request *req)
	{
	unsigned long flags;

	if (req->nbytes < 2 \|\| req->data[0] != ADB_PACKET \|\| req->nbytes > 15) {
	req->complete = 1;
	return -EINVAL;
	}

	req->next = 0;
	req->sent = 0;
	req->complete = 0;
	req->reply_len = 0;

	local_irq_save(flags);

	if (current_req != NULL) {
	last_req->next = req;
	last_req = req;
	} else {
	current_req = req;
	last_req = req;
	if (macii_state == idle) macii_start();
	}

	local_irq_restore(flags);
	return 0;
	}

	/* Start auto-polling */
	static int macii_autopoll(int devs)
	{
	/* Just ping a random default address */
	if (!(current_req \|\| retry_req))
	macii_retransmit( (last_active < 16 && last_active > 0) ? last_active : 3);
	return 0;
	}

	/* Prod the chip without interrupts */
	static void macii_poll(void)
	{
	unsigned long flags;

	local_irq_save(flags);
	if (via[IFR] & SR_INT) macii_interrupt(0, 0, 0);
	local_irq_restore(flags);
	}

	/* Reset the bus */
	static int macii_reset_bus(void)
	{
	static struct adb_request req;

	/* Command = 0, Address = ignored */
	adb_request(&req, NULL, 0, 1, ADB_BUSRESET);

	return 0;
	}

	/* Start sending ADB packet */
	static void macii_start(void)
	{
	unsigned long flags;
	struct adb_request *req;

	req = current_req;
	if (!req) return;

	/* assert macii_state == idle */
	if (macii_state != idle) {
	printk("macii_start: called while driver busy (%p %x %x)!\n",
	req, macii_state, (uint) via1[B] & (ST_MASK\|TREQ));
	return;
	}

	local_irq_save(flags);

	/*
	* IRQ signaled ?? (means ADB controller wants to send, or might
	* be end of packet if we were reading)
	*/
	#if 0 /* FIXME: This is broke broke broke, for some reason */
	if ((via[B] & TREQ) == 0) {
	printk("macii_start: weird poll stuff. huh?\n");
	/*
	* FIXME - we need to restart this on a timer
	* or a collision at boot hangs us.
	* Never set macii_state to idle here, or macii_start
	* won't be called again from send_request!
	* (need to re-check other cases ...)
	*/
	/*
	* if the interrupt handler set the need_poll
	* flag, it's hopefully a SRQ poll or re-Talk
	* so we try to send here anyway
	*/
	if (!need_poll) {
	if (console_loglevel == 10)
	printk("macii_start: device busy - retry %p state %d status %x!\n",
	req, macii_state,
	(uint) via[B] & (ST_MASK\|TREQ));
	retry_req = req;
	/* set ADB status here ? */
	local_irq_restore(flags);
	return;
	} else {
	need_poll = 0;
	}
	}
	#endif
	/*
	* Another retry pending? (sanity check)
	*/
	if (retry_req) {
	retry_req = NULL;
	}

	/* Now send it. Be careful though, that first byte of the request */
	/* is actually ADB_PACKET; the real data begins at index 1! */

	/* store command byte */
	command_byte = req->data[1];
	/* Output mode */
	via[ACR] \|= SR_OUT;
	/* Load data */
	via[SR] = req->data[1];
	/* set ADB state to 'command' */
	via[B] = (via[B] & ~ST_MASK) \| ST_CMD;

	macii_state = sending;
	data_index = 2;

	local_irq_restore(flags);
	}

	/*
	* The notorious ADB interrupt handler - does all of the protocol handling,
	* except for starting new send operations. Relies heavily on the ADB
	* controller sending and receiving data, thereby generating SR interrupts
	* for us. This means there has to be always activity on the ADB bus, otherwise
	* the whole process dies and has to be re-kicked by sending TALK requests ...
	* CUDA-based Macs seem to solve this with the autopoll option, for MacII-type
	* ADB the problem isn't solved yet (retransmit of the latest active TALK seems
	* a good choice; either on timeout or on a timer interrupt).
	*
	* The basic ADB state machine was left unchanged from the original MacII code
	* by Alan Cox, which was based on the CUDA driver for PowerMac.
	* The syntax of the ADB status lines seems to be totally different on MacII,
	* though. MacII uses the states Command -> Even -> Odd -> Even ->...-> Idle for
	* sending, and Idle -> Even -> Odd -> Even ->...-> Idle for receiving. Start
	* and end of a receive packet are signaled by asserting /IRQ on the interrupt
	* line. Timeouts are signaled by a sequence of 4 0xFF, with /IRQ asserted on
	* every other byte. SRQ is probably signaled by 3 or more 0xFF tacked on the
	* end of a packet. (Thanks to Guido Koerber for eavesdropping on the ADB
	* protocol with a logic analyzer!!)
	*
	* Note: As of 21/10/97, the MacII ADB part works including timeout detection
	* and retransmit (Talk to the last active device).
	*/
	static irqreturn_t macii_interrupt(int irq, void arg, struct pt_regs regs)
	{
	int x, adbdir;
	unsigned long flags;
	struct adb_request *req;

	last_status = status;

	/* prevent races due to SCSI enabling ints */
	local_irq_save(flags);

	if (driver_running) {
	local_irq_restore(flags);
	return IRQ_NONE;
	}

	driver_running = 1;

	status = via[B] & (ST_MASK\|TREQ);
	adbdir = via[ACR] & SR_OUT;

	switch (macii_state) {
	case idle:
	x = via[SR];
	first_byte = x;
	/* set ADB state = even for first data byte */
	via[B] = (via[B] & ~ST_MASK) \| ST_EVEN;

	reply_buf[0] = first_byte; /* was command_byte?? */
	reply_ptr = reply_buf + 1;
	reply_len = 1;
	prefix_len = 1;
	reading_reply = 0;

	macii_state = reading;
	break;

	case awaiting_reply:
	/* handshake etc. for II ?? */
	x = via[SR];
	first_byte = x;
	/* set ADB state = even for first data byte */
	via[B] = (via[B] & ~ST_MASK) \| ST_EVEN;

	current_req->reply[0] = first_byte;
	reply_ptr = current_req->reply + 1;
	reply_len = 1;
	prefix_len = 1;
	reading_reply = 1;

	macii_state = reading;
	break;

	case sending:
	req = current_req;
	if (data_index >= req->nbytes) {
	/* print an error message if a listen command has no data */
	if (((command_byte & 0x0C) == 0x08)
	/* && (console_loglevel == 10) */
	&& (data_index == 2))
	printk("MacII ADB: listen command with no data: %x!\n",
	command_byte);
	/* reset to shift in */
	via[ACR] &= ~SR_OUT;
	x = via[SR];
	/* set ADB state idle - might get SRQ */
	via[B] = (via[B] & ~ST_MASK) \| ST_IDLE;

	req->sent = 1;

	if (req->reply_expected) {
	macii_state = awaiting_reply;
	} else {
	req->complete = 1;
	current_req = req->next;
	if (req->done) (*req->done)(req);
	macii_state = idle;
	if (current_req \|\| retry_req)
	macii_start();
	else
	macii_retransmit((command_byte & 0xF0) >> 4);
	}
	} else {
	via[SR] = req->data[data_index++];

	if ( (via[B] & ST_MASK) == ST_CMD ) {
	/* just sent the command byte, set to EVEN */
	via[B] = (via[B] & ~ST_MASK) \| ST_EVEN;
	} else {
	/* invert state bits, toggle ODD/EVEN */
	via[B] ^= ST_MASK;
	}
	}
	break;

	case reading:

	/* timeout / SRQ handling for II hw */
	if( (first_byte == 0xFF && (reply_len-prefix_len)==2
	&& memcmp(reply_ptr-2,"\xFF\xFF",2)==0) \|\|
	((reply_len-prefix_len)==3
	&& memcmp(reply_ptr-3,"\xFF\xFF\xFF",3)==0))
	{
	/*
	* possible timeout (in fact, most probably a
	* timeout, since SRQ can't be signaled without
	* transfer on the bus).
	* The last three bytes seen were FF, together
	* with the starting byte (in case we started
	* on 'idle' or 'awaiting_reply') this probably
	* makes four. So this is mostl likely #5!
	* The timeout signal is a pattern 1 0 1 0 0..
	* on /INT, meaning we missed it :-(
	*/
	x = via[SR];
	if (x != 0xFF) printk("MacII ADB: mistaken timeout/SRQ!\n");

	if ((status & TREQ) == (last_status & TREQ)) {
	/* Not a timeout. Unsolicited SRQ? weird. */
	/* Terminate the SRQ packet and poll */
	need_poll = 1;
	}
	/* There's no packet to get, so reply is blank */
	via[B] ^= ST_MASK;
	reply_ptr -= (reply_len-prefix_len);
	reply_len = prefix_len;
	macii_state = read_done;
	break;
	} /* end timeout / SRQ handling for II hw. */

	if((reply_len-prefix_len)>3
	&& memcmp(reply_ptr-3,"\xFF\xFF\xFF",3)==0)
	{
	/* SRQ tacked on data packet */
	/* Terminate the packet (SRQ never ends) */
	x = via[SR];
	macii_state = read_done;
	reply_len -= 3;
	reply_ptr -= 3;
	need_poll = 1;
	/* need to continue; next byte not seen else */
	} else {
	/* Sanity check */
	if (reply_len > 15) reply_len = 0;
	/* read byte */
	x = via[SR];
	*reply_ptr = x;
	reply_ptr++;
	reply_len++;
	}
	/* The usual handshake ... */

	/*
	* NetBSD hints that the next to last byte
	* is sent with IRQ !!
	* Guido found out it's the last one (0x0),
	* but IRQ should be asserted already.
	* Problem with timeout detection: First
	* transition to /IRQ might be second
	* byte of timeout packet!
	* Timeouts are signaled by 4x FF.
	*/
	if (((status & TREQ) == 0) && (x == 0x00)) { /* != 0xFF */
	/* invert state bits, toggle ODD/EVEN */
	via[B] ^= ST_MASK;

	/* adjust packet length */
	reply_len--;
	reply_ptr--;
	macii_state = read_done;
	} else {
	/* not caught: ST_CMD */
	/* required for re-entry 'reading'! */
	if ((status & ST_MASK) == ST_IDLE) {
	/* (in)sanity check - set even */
	via[B] = (via[B] & ~ST_MASK) \| ST_EVEN;
	} else {
	/* invert state bits */
	via[B] ^= ST_MASK;
	}
	}
	break;

	case read_done:
	x = via[SR];
	if (reading_reply) {
	req = current_req;
	req->reply_len = reply_ptr - req->reply;
	req->complete = 1;
	current_req = req->next;
	if (req->done) (*req->done)(req);
	} else {
	adb_input(reply_buf, reply_ptr - reply_buf,
	regs, 0);
	}

	/*
	* remember this device ID; it's the latest we got a
	* reply from!
	*/
	last_reply = command_byte;
	last_active = (command_byte & 0xF0) >> 4;

	/* SRQ seen before, initiate poll now */
	if (need_poll) {
	macii_state = idle;
	macii_queue_poll();
	need_poll = 0;
	break;
	}

	/* set ADB state to idle */
	via[B] = (via[B] & ~ST_MASK) \| ST_IDLE;

	/* /IRQ seen, so the ADB controller has data for us */
	if ((via[B] & TREQ) != 0) {
	macii_state = reading;

	reply_buf[0] = command_byte;
	reply_ptr = reply_buf + 1;
	reply_len = 1;
	prefix_len = 1;
	reading_reply = 0;
	} else {
	/* no IRQ, send next packet or wait */
	macii_state = idle;
	if (current_req)
	macii_start();
	else
	macii_retransmit(last_active);
	}
	break;

	default:
	break;
	}
	/* reset mutex and interrupts */
	driver_running = 0;
	local_irq_restore(flags);
	return IRQ_HANDLED;
	}