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* Device driver for the via ADB on (many) Mac II-class machines
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* Based on the original ADB keyboard handler Copyright (c) 1997 Alan Cox
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* Also derived from code Copyright (C) 1996 Paul Mackerras.
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* With various updates provided over the years by Michael Schmitz,
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* Guideo Koerber and others.
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* Rewrite for Unified ADB by Joshua M. Thompson (funaho@jurai.org)
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* 1999-08-02 (jmt) - Initial rewrite for Unified ADB.
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* 2000-03-29 Tony Mantler <tonym@mac.linux-m68k.org>
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* - Big overhaul, should actually work now.
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* 2006-12-31 Finn Thain <fthain@telegraphics.com.au> - Another overhaul.
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* Inside Macintosh, ch. 5 ADB Manager
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* Guide to the Macinstosh Family Hardware, ch. 8 Apple Desktop Bus
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* Rockwell R6522 VIA datasheet
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* Apple's "ADB Analyzer" bus sniffer is invaluable:
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* ftp://ftp.apple.com/developer/Tool_Chest/Devices_-_Hardware/Apple_Desktop_Bus/
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#include <linux/types.h>
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#include <linux/errno.h>
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#include <linux/kernel.h>
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#include <linux/delay.h>
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#include <linux/adb.h>
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#include <linux/interrupt.h>
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#include <linux/init.h>
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#include <asm/macintosh.h>
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#include <asm/macints.h>
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#include <asm/mac_via.h>
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#include <asm/system.h>
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static volatile unsigned char *via;
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/* VIA registers - spaced 0x200 bytes apart */
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#define RS 0x200 /* skip between registers */
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#define B 0 /* B-side data */
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#define A RS /* A-side data */
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#define DIRB (2*RS) /* B-side direction (1=output) */
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#define DIRA (3*RS) /* A-side direction (1=output) */
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#define T1CL (4*RS) /* Timer 1 ctr/latch (low 8 bits) */
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#define T1CH (5*RS) /* Timer 1 counter (high 8 bits) */
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#define T1LL (6*RS) /* Timer 1 latch (low 8 bits) */
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#define T1LH (7*RS) /* Timer 1 latch (high 8 bits) */
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#define T2CL (8*RS) /* Timer 2 ctr/latch (low 8 bits) */
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#define T2CH (9*RS) /* Timer 2 counter (high 8 bits) */
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#define SR (10*RS) /* Shift register */
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#define ACR (11*RS) /* Auxiliary control register */
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#define PCR (12*RS) /* Peripheral control register */
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#define IFR (13*RS) /* Interrupt flag register */
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#define IER (14*RS) /* Interrupt enable register */
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#define ANH (15*RS) /* A-side data, no handshake */
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/* Bits in B data register: all active low */
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#define CTLR_IRQ 0x08 /* Controller rcv status (input) */
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#define ST_MASK 0x30 /* mask for selecting ADB state bits */
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#define SR_CTRL 0x1c /* Shift register control bits */
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#define SR_EXT 0x0c /* Shift on external clock */
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#define SR_OUT 0x10 /* Shift out if 1 */
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/* Bits in IFR and IER */
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#define IER_SET 0x80 /* set bits in IER */
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#define IER_CLR 0 /* clear bits in IER */
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#define SR_INT 0x04 /* Shift register full/empty */
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/* ADB transaction states according to GMHW */
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#define ST_CMD 0x00 /* ADB state: command byte */
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#define ST_EVEN 0x10 /* ADB state: even data byte */
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#define ST_ODD 0x20 /* ADB state: odd data byte */
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#define ST_IDLE 0x30 /* ADB state: idle, nothing to send */
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static int macii_init_via(void);
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static void macii_start(void);
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static irqreturn_t macii_interrupt(int irq, void *arg);
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static void macii_queue_poll(void);
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static int macii_probe(void);
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static int macii_init(void);
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static int macii_send_request(struct adb_request *req, int sync);
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static int macii_write(struct adb_request *req);
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static int macii_autopoll(int devs);
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static void macii_poll(void);
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static int macii_reset_bus(void);
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struct adb_driver via_macii_driver = {
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static enum macii_state {
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static struct adb_request *current_req; /* first request struct in the queue */
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static struct adb_request *last_req; /* last request struct in the queue */
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static unsigned char reply_buf[16]; /* storage for autopolled replies */
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static unsigned char *reply_ptr; /* next byte in reply_buf or req->reply */
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static int reading_reply; /* store reply in reply_buf else req->reply */
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static int data_index; /* index of the next byte to send from req->data */
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static int reply_len; /* number of bytes received in reply_buf or req->reply */
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static int status; /* VIA's ADB status bits captured upon interrupt */
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static int last_status; /* status bits as at previous interrupt */
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static int srq_asserted; /* have to poll for the device that asserted it */
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static int command_byte; /* the most recent command byte transmitted */
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static int autopoll_devs; /* bits set are device addresses to be polled */
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/* Sanity check for request queue. Doesn't check for cycles. */
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static int request_is_queued(struct adb_request *req) {
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struct adb_request *cur;
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local_irq_save(flags);
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local_irq_restore(flags);
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local_irq_restore(flags);
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/* Check for MacII style ADB */
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static int macii_probe(void)
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if (macintosh_config->adb_type != MAC_ADB_II) return -ENODEV;
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printk("adb: Mac II ADB Driver v1.0 for Unified ADB\n");
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/* Initialize the driver */
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local_irq_save(flags);
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err = macii_init_via();
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err = request_irq(IRQ_MAC_ADB, macii_interrupt, 0, "ADB",
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local_irq_restore(flags);
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/* initialize the hardware */
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static int macii_init_via(void)
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/* We want CTLR_IRQ as input and ST_EVEN | ST_ODD as output lines. */
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via[DIRB] = (via[DIRB] | ST_EVEN | ST_ODD) & ~CTLR_IRQ;
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/* Set up state: idle */
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last_status = via[B] & (ST_MASK|CTLR_IRQ);
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/* Shift register on input */
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via[ACR] = (via[ACR] & ~SR_CTRL) | SR_EXT;
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/* Wipe any pending data and int */
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/* Send an ADB poll (Talk Register 0 command prepended to the request queue) */
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static void macii_queue_poll(void)
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/* No point polling the active device as it will never assert SRQ, so
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* poll the next device in the autopoll list. This could leave us
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* stuck in a polling loop if an unprobed device is asserting SRQ.
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* In theory, that could only happen if a device was plugged in after
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* probing started. Unplugging it again will break the cycle.
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* (Simply polling the next higher device often ends up polling almost
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* every device (after wrapping around), which takes too long.)
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static struct adb_request req;
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if (!autopoll_devs) return;
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device_mask = (1 << (((command_byte & 0xF0) >> 4) + 1)) - 1;
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if (autopoll_devs & ~device_mask)
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next_device = ffs(autopoll_devs & ~device_mask) - 1;
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next_device = ffs(autopoll_devs) - 1;
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BUG_ON(request_is_queued(&req));
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adb_request(&req, NULL, ADBREQ_NOSEND, 1,
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ADB_READREG(next_device, 0));
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req.next = current_req;
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if (current_req != NULL) {
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/* Send an ADB request; if sync, poll out the reply 'till it's done */
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static int macii_send_request(struct adb_request *req, int sync)
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BUG_ON(request_is_queued(req));
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local_irq_save(flags);
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err = macii_write(req);
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local_irq_restore(flags);
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while (!req->complete) {
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BUG_ON(request_is_queued(req));
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/* Send an ADB request (append to request queue) */
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static int macii_write(struct adb_request *req)
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if (req->nbytes < 2 || req->data[0] != ADB_PACKET || req->nbytes > 15) {
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if (current_req != NULL) {
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last_req->next = req;
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if (macii_state == idle) macii_start();
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/* Start auto-polling */
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static int macii_autopoll(int devs)
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static struct adb_request req;
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/* bit 1 == device 1, and so on. */
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autopoll_devs = devs & 0xFFFE;
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if (!autopoll_devs) return 0;
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local_irq_save(flags);
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if (current_req == NULL) {
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/* Send a Talk Reg 0. The controller will repeatedly transmit
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* this as long as it is idle.
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adb_request(&req, NULL, ADBREQ_NOSEND, 1,
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ADB_READREG(ffs(autopoll_devs) - 1, 0));
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err = macii_write(&req);
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local_irq_restore(flags);
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static inline int need_autopoll(void) {
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/* Was the last command Talk Reg 0
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* and is the target on the autopoll list?
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if ((command_byte & 0x0F) == 0x0C &&
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((1 << ((command_byte & 0xF0) >> 4)) & autopoll_devs))
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/* Prod the chip without interrupts */
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static void macii_poll(void)
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disable_irq(IRQ_MAC_ADB);
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macii_interrupt(0, NULL);
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enable_irq(IRQ_MAC_ADB);
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static int macii_reset_bus(void)
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static struct adb_request req;
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if (request_is_queued(&req))
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/* Command = 0, Address = ignored */
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adb_request(&req, NULL, 0, 1, ADB_BUSRESET);
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/* Don't want any more requests during the Global Reset low time. */
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/* Start sending ADB packet */
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static void macii_start(void)
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struct adb_request *req;
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BUG_ON(macii_state != idle);
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/* Now send it. Be careful though, that first byte of the request
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* is actually ADB_PACKET; the real data begins at index 1!
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* And req->nbytes is the number of bytes of real data plus one.
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/* store command byte */
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command_byte = req->data[1];
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via[SR] = req->data[1];
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/* set ADB state to 'command' */
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via[B] = (via[B] & ~ST_MASK) | ST_CMD;
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macii_state = sending;
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* The notorious ADB interrupt handler - does all of the protocol handling.
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* Relies on the ADB controller sending and receiving data, thereby
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* generating shift register interrupts (SR_INT) for us. This means there has
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* to be activity on the ADB bus. The chip will poll to achieve this.
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* The basic ADB state machine was left unchanged from the original MacII code
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* by Alan Cox, which was based on the CUDA driver for PowerMac.
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* The syntax of the ADB status lines is totally different on MacII,
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* though. MacII uses the states Command -> Even -> Odd -> Even ->...-> Idle
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* for sending and Idle -> Even -> Odd -> Even ->...-> Idle for receiving.
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* Start and end of a receive packet are signalled by asserting /IRQ on the
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* interrupt line (/IRQ means the CTLR_IRQ bit in port B; not to be confused
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* with the VIA shift register interrupt. /IRQ never actually interrupts the
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* processor, it's just an ordinary input.)
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static irqreturn_t macii_interrupt(int irq, void *arg)
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struct adb_request *req;
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/* Clear the SR IRQ flag when polling. */
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if (via[IFR] & SR_INT)
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last_status = status;
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status = via[B] & (ST_MASK|CTLR_IRQ);
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switch (macii_state) {
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reply_ptr = current_req->reply;
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BUG_ON(current_req != NULL);
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reply_ptr = reply_buf;
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if ((status & CTLR_IRQ) && (x == 0xFF)) {
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/* Bus timeout without SRQ sequence:
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* data is "FF" while CTLR_IRQ is "H"
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macii_state = read_done;
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macii_state = reading;
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/* set ADB state = even for first data byte */
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via[B] = (via[B] & ~ST_MASK) | ST_EVEN;
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if (data_index >= req->nbytes) {
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if (req->reply_expected) {
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current_req = req->next;
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if (req->done) (*req->done)(req);
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macii_autopoll(autopoll_devs);
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if (macii_state == idle) {
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/* reset to shift in */
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/* set ADB state idle - might get SRQ */
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via[B] = (via[B] & ~ST_MASK) | ST_IDLE;
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via[SR] = req->data[data_index++];
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if ( (via[B] & ST_MASK) == ST_CMD ) {
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/* just sent the command byte, set to EVEN */
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via[B] = (via[B] & ~ST_MASK) | ST_EVEN;
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/* invert state bits, toggle ODD/EVEN */
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BUG_ON((status & ST_MASK) == ST_CMD ||
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(status & ST_MASK) == ST_IDLE);
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/* Bus timeout with SRQ sequence:
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* data is "XX FF" while CTLR_IRQ is "L L"
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* End of packet without SRQ sequence:
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* data is "XX...YY 00" while CTLR_IRQ is "L...H L"
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* End of packet SRQ sequence:
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* data is "XX...YY 00" while CTLR_IRQ is "L...L L"
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* (where XX is the first response byte and
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* YY is the last byte of valid response data.)
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if (!(status & CTLR_IRQ)) {
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if (!(last_status & CTLR_IRQ)) {
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macii_state = read_done;
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} else if (x == 0x00) {
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macii_state = read_done;
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if (!(last_status & CTLR_IRQ))
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if (macii_state == reading) {
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BUG_ON(reply_len > 15);
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/* invert state bits, toggle ODD/EVEN */
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req->reply_len = reply_len;
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current_req = req->next;
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if (req->done) (*req->done)(req);
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} else if (reply_len && autopoll_devs)
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adb_input(reply_buf, reply_len, 0);
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/* SRQ seen before, initiate poll now */
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macii_autopoll(autopoll_devs);
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if (macii_state == idle)
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via[B] = (via[B] & ~ST_MASK) | ST_IDLE;