pc110pad.c

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/*
 *	Linux driver for the PC110 pad
 */
 
/**
 * 	DOC: PC110 Digitizer Hardware
 *
 *	The pad provides triples of data. The first byte has
 *	0x80=bit 8 X, 0x01=bit 7 X, 0x08=bit 8 Y, 0x01=still down
 *	The second byte is bits 0-6 X
 *	The third is bits 0-6 Y
 *
 *	This is read internally and used to synthesize a stream of
 *	triples in the form expected from a PS/2 device. Specialist
 *	applications can choose to obtain the pad data in other formats
 *	including a debugging mode.
 *
 *	It would be good to add a joystick driver mode to this pad so
 *	that doom and other game playing are better. One possible approach
 *	would be to deactive the mouse mode while the joystick port is opened.
 */
 
/*
 *	History
 *
 *	0.0 1997-05-16 Alan Cox <[e-mail]> - Pad reader
 *	0.1 1997-05-19 Robin O'Leary <[e-mail]> - PS/2 emulation
 *	0.2 1997-06-03 Robin O'Leary <[e-mail]> - tap gesture
 *	0.3 1997-06-27 Alan Cox <[e-mail]> - 2.1 commit
 *	0.4 1997-11-09 Alan Cox <[e-mail]> - Single Unix VFS API changes
 *	0.5 2000-02-10 Alan Cox <[e-mail]> - 2.3.x cleanup, documentation
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/signal.h>
#include <linux/errno.h>
#include <linux/mm.h>
#include <linux/miscdevice.h>
#include <linux/ptrace.h>
#include <linux/poll.h>
#include <linux/ioport.h>
#include <linux/interrupt.h>
#include <linux/smp_lock.h>
#include <linux/init.h>

#include <asm/signal.h>
#include <asm/io.h>
#include <asm/irq.h>
#include <asm/semaphore.h>
#include <linux/spinlock.h>
#include <asm/uaccess.h>

#include "pc110pad.h"


static struct pc110pad_params default_params = {
	mode:			PC110PAD_PS2,
	bounce_interval:	50 MS,
	tap_interval:		200 MS,
	irq:			10,
	io:			0x15E0,
};

static struct pc110pad_params current_params;


/* driver/filesystem interface management */
static wait_queue_head_t queue;
static struct fasync_struct *asyncptr;
static int active;	/* number of concurrent open()s */
static struct semaphore reader_lock;

/**
 *	wake_readers:
 *
 *	Take care of letting any waiting processes know that
 *	now would be a good time to do a read().  Called
 *	whenever a state transition occurs, real or synthetic. Also
 *	issue any SIGIO's to programs that use SIGIO on mice (eg
 *	Executor)
 */
 
static void wake_readers(void)
{
	wake_up_interruptible(&queue);
	kill_fasync(&asyncptr, SIGIO, POLL_IN);
}


/*****************************************************************************/
/*
 * Deal with the messy business of synthesizing button tap and drag
 * events.
 *
 * Exports:
 *	notify_pad_up_down()
 *		Must be called whenever debounced pad up/down state changes.
 *	button_pending
 *		Flag is set whenever read_button() has new values
 *		to return.
 *	read_button()
 *		Obtains the current synthetic mouse button state.
 */

/*
 * These keep track of up/down transitions needed to generate the
 * synthetic mouse button events.  While recent_transition is set,
 * up/down events cause transition_count to increment.  tap_timer
 * turns off the recent_transition flag and may cause some synthetic
 * up/down mouse events to be created by incrementing synthesize_tap.
 */
 
static int button_pending;
static int recent_transition;
static int transition_count;
static int synthesize_tap;
static void tap_timeout(unsigned long data);
static struct timer_list tap_timer = { function: tap_timeout };


/**
 * tap_timeout:
 * @data: Unused
 *
 * This callback goes off a short time after an up/down transition;
 * before it goes off, transitions will be considered part of a
 * single PS/2 event and counted in transition_count.  Once the
 * timeout occurs the recent_transition flag is cleared and
 * any synthetic mouse up/down events are generated.
 */
 
static void tap_timeout(unsigned long data)
{
	if(!recent_transition)
	{
		printk(KERN_ERR "pc110pad: tap_timeout but no recent transition!\n");
	}
	if( transition_count==2 || transition_count==4 || transition_count==6 )
	{
		synthesize_tap+=transition_count;
		button_pending = 1;
		wake_readers();
	}
	recent_transition=0;
}


/**
 * notify_pad_up_down:
 *
 * Called by the raw pad read routines when a (debounced) up/down
 * transition is detected.
 */
 
void notify_pad_up_down(void)
{
	if(recent_transition)
	{
		transition_count++;
	}
	else
	{
		transition_count=1;
		recent_transition=1;
	}
	mod_timer(&tap_timer, jiffies + current_params.tap_interval);

	/* changes to transition_count can cause reported button to change */
	button_pending = 1;
	wake_readers();
}

/**
 *	read_button:
 *	@b: pointer to the button status.
 *
 *	The actual button state depends on what we are seeing. We have to check
 *	for the tap gesture and also for dragging.
 */

static void read_button(int *b)
{
	if(synthesize_tap)
	{
		*b=--synthesize_tap & 1;
	}
	else
	{
		*b=(!recent_transition && transition_count==3);	/* drag */
	}
	button_pending=(synthesize_tap>0);
}


/*****************************************************************************/
/*
 * Read pad absolute co-ordinates and debounced up/down state.
 *
 * Exports:
 *	pad_irq()
 *		Function to be called whenever the pad signals
 *		that it has new data available.
 *	read_raw_pad()
 *		Returns the most current pad state.
 *	xy_pending
 *		Flag is set whenever read_raw_pad() has new values
 *		to return.
 * Imports:
 *	wake_readers()
 *		Called when movement occurs.
 *	notify_pad_up_down()
 *		Called when debounced up/down status changes.
 */

/*
 * These are up/down state and absolute co-ords read directly from pad 
 */

static int raw_data[3];
static int raw_data_count;
static int raw_x, raw_y;	/* most recent absolute co-ords read */
static int raw_down;		/* raw up/down state */
static int debounced_down;	/* up/down state after debounce processing */
static enum { NO_BOUNCE, JUST_GONE_UP, JUST_GONE_DOWN } bounce=NO_BOUNCE;
				/* set just after an up/down transition */
static int xy_pending;	/* set if new data have not yet been read */

/* 
 * Timer goes off a short while after an up/down transition and copies
 * the value of raw_down to debounced_down.
 */
 
static void bounce_timeout(unsigned long data);
static struct timer_list bounce_timer = { function: bounce_timeout };



/**
 * bounce_timeout:
 * @data: Unused
 *
 * No further up/down transitions happened within the
 * bounce period, so treat this as a genuine transition.
 */

static void bounce_timeout(unsigned long data)
{
	switch(bounce)
	{
		case NO_BOUNCE:
		{
			/*
			 * Strange; the timer callback should only go off if
			 * we were expecting to do bounce processing!
			 */
			printk(KERN_WARNING "pc110pad, bounce_timeout: bounce flag not set!\n");
			break;
		}
		case JUST_GONE_UP:
		{
			/*
			 * The last up we spotted really was an up, so set
			 * debounced state the same as raw state.
			 */
			bounce=NO_BOUNCE;
			if(debounced_down==raw_down)
			{
				printk(KERN_WARNING "pc110pad, bounce_timeout: raw already debounced!\n");
			}
			debounced_down=raw_down;

			notify_pad_up_down();
			break;
		}
		case JUST_GONE_DOWN:
		{
			/*
			 * We don't debounce down events, but we still time
			 * out soon after one occurs so we can avoid the (x,y)
			 * skittering that sometimes happens.
			 */
			bounce=NO_BOUNCE;
			break;
		}
	}
}


/**
 * pad_irq:
 * @irq: Interrupt number
 * @ptr: Unused
 * @regs: Unused
 *
 * Callback when pad's irq goes off; copies values in to raw_* globals;
 * initiates debounce processing. This isn't SMP safe however there are
 * no SMP machines with a PC110 touchpad on them.
 */
 
static void pad_irq(int irq, void *ptr, struct pt_regs *regs)
{

	/* Obtain byte from pad and prime for next byte */
	{
		int value=inb_p(current_params.io);
		int handshake=inb_p(current_params.io+2);
		outb_p(handshake | 1, current_params.io+2);
		outb_p(handshake &~1, current_params.io+2);
		inb_p(0x64);

		raw_data[raw_data_count++]=value;
	}

	if(raw_data_count==3)
	{
		int new_down=raw_data[0]&0x01;
		int new_x=raw_data[1];
		int new_y=raw_data[2];
		if(raw_data[0]&0x10) new_x+=128;
		if(raw_data[0]&0x80) new_x+=256;
		if(raw_data[0]&0x08) new_y+=128;

		if( (raw_x!=new_x) || (raw_y!=new_y) )
		{
			raw_x=new_x;
			raw_y=new_y;
			xy_pending=1;
		}

		if(new_down != raw_down)
		{
			/* Down state has changed.  raw_down always holds
			 * the most recently observed state.
			 */
			raw_down=new_down;

			/* Forget any earlier bounce processing */
			if(bounce)
			{
				del_timer(&bounce_timer);
				bounce=NO_BOUNCE;
			}

			if(new_down)
			{
				if(debounced_down)
				{
					/* pad gone down, but we were reporting
					 * it down anyway because we suspected
					 * (correctly) that the last up was just
					 * a bounce
					 */
				}
				else
				{
					bounce=JUST_GONE_DOWN;
					mod_timer(&bounce_timer,
						jiffies+current_params.bounce_interval);
					/* start new stroke/tap */
					debounced_down=new_down;
					notify_pad_up_down();
				}
			}
			else /* just gone up */
			{
				if(recent_transition)
				{
					/* early bounces are probably part of
					 * a multi-tap gesture, so process
					 * immediately
					 */
					debounced_down=new_down;
					notify_pad_up_down();
				}
				else
				{
					/* don't trust it yet */
					bounce=JUST_GONE_UP;
					mod_timer(&bounce_timer,
						jiffies+current_params.bounce_interval);
				}
			}
		}
		wake_readers();
		raw_data_count=0;
	}
}

/**
 *	read_raw_pad:
 *	@down: set if the pen is down
 *	@debounced: set if the debounced pen position is down
 *	@x: X position
 *	@y: Y position
 *
 *	Retrieve the data saved by the interrupt handler and indicate we
 *	have no more pending XY to do. 
 *
 *	FIXME: We should switch to a spinlock for this.
 */

static void read_raw_pad(int *down, int *debounced, int *x, int *y)
{
	disable_irq(current_params.irq);
	{
		*down=raw_down;
		*debounced=debounced_down;
		*x=raw_x;
		*y=raw_y;
		xy_pending = 0;
	}
	enable_irq(current_params.irq);
}

/*****************************************************************************/
/*
 * Filesystem interface
 */

/* 
 * Read returns byte triples, so we need to keep track of
 * how much of a triple has been read.  This is shared across
 * all processes which have this device open---not that anything
 * will make much sense in that case.