ps2 keyboard filter hook

[ddstreet@us.ibm.com]

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IBM Retail Store Solutions dept has certain PS/2 keyboards which extend the
standard PS/2 specification in order to support addition hardware built into the
keyboard (such as a Magnetic Strip Reader, Keylock, Tone generator, extra keys,
extra LEDs, etc).  This addition hardware behaves in a manner that makes it
unusable if driven by a standard PS/2 driver (sadly, due to the fact that its
design is "IP" I can't elaborate on how or why it is incompatible with the
standard PS/2 specification).

In order to use these keyboards, a the standard PS/2 driver needs to behave a
bit differently; thus attached is a modifcation to the PS/2 driver which allows
other drivers to register with the PS/2 driver as 'filters'.  There is a
arbitrary max number of 'filters' set to 1, which is a compile-time define.
The registered drivers are called (in order of registration) for every scancode,
and they may change or consume the scancode (or allow it to pass).  Also the
'filters' are given a function to send an variable-sized buffer to the keyboard
output port; this function is synchronized using a semaphore which also
coordinates with pckbd_leds().

-Dan

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diff -urN 2.4.5-clean/Documentation/Configure.help linux/Documentation/Configure.help
--- 2.4.5-clean/Documentation/Configure.help	Thu May 24 18:03:06 2001
+++ linux/Documentation/Configure.help	Fri Jun 15 13:34:18 2001
@@ -13274,6 +13274,21 @@
   If you are unsure, say N and read the HOWTO nevertheless: it will
   tell you what you have.
 
+PS/2 Keyboard Filter support
+CONFIG_PC_KEYB_FILTER
+  This enables filter support in the PS/2 keyboard driver.  With
+  this enabled, other drivers will be able to register with the
+  PS/2 driver and filter all incoming scancodes.  This is useful
+  for keyboards which extend the PS/2 keyboard standard with
+  non-standard scancodes which should not be normally routed to
+  the current console.
+
+  This option does not actually filter any scancodes, it only
+  allows other drivers (who will do the filtering) to register
+  with the PS/2 driver.
+
+  If unsure, say N.
+
 QIC-02 tape support
 CONFIG_QIC02_TAPE
   If you have a non-SCSI tape drive like that, say Y. Or, if you want
diff -urN 2.4.5-clean/drivers/char/Config.in linux/drivers/char/Config.in
--- 2.4.5-clean/drivers/char/Config.in	Tue Mar  6 22:44:34 2001
+++ linux/drivers/char/Config.in	Fri Jun 15 13:34:18 2001
@@ -105,6 +105,11 @@
 
 source drivers/char/joystick/Config.in
 
+mainmenu_option next_comment
+comment 'Keyboards'
+bool 'PS/2 Keyboard Filter support' CONFIG_PC_KEYB_FILTER
+endmenu
+
 tristate 'QIC-02 tape support' CONFIG_QIC02_TAPE
 if [ "$CONFIG_QIC02_TAPE" != "n" ]; then
    bool '  Do you want runtime configuration for QIC-02' CONFIG_QIC02_DYNCONF
diff -urN 2.4.5-clean/drivers/char/Makefile linux/drivers/char/Makefile
--- 2.4.5-clean/drivers/char/Makefile	Wed May 16 13:27:02 2001
+++ linux/drivers/char/Makefile	Fri Jun 15 13:34:18 2001
@@ -21,7 +21,7 @@
 # All of the (potential) objects that export symbols.
 # This list comes from 'grep -l EXPORT_SYMBOL *.[hc]'.
 
-export-objs     :=	busmouse.o console.o keyboard.o sysrq.o \
+export-objs     :=	busmouse.o console.o keyboard.o pc_keyb.o sysrq.o \
 			misc.o pty.o random.o selection.o serial.o \
 			tty_io.o
 
diff -urN 2.4.5-clean/drivers/char/pc_keyb.c linux/drivers/char/pc_keyb.c
--- 2.4.5-clean/drivers/char/pc_keyb.c	Fri Apr  6 13:42:55 2001
+++ linux/drivers/char/pc_keyb.c	Fri Jun 15 13:34:18 2001
@@ -13,6 +13,11 @@
  * Code fixes to handle mouse ACKs properly.
  * C. Scott Ananian <cananian@alumni.princeton.edu> 1999-01-29.
  *
+ * Added optional scancode filtering, used in keyboards which
+ * (incompatibly) extend the standard PS/2 specification.
+ * Also added synchronized output writing using a semaphore.
+ * Dan Streetman <ddstreet@us.ibm.com> 2001-03-14
+ *
  */
 
 #include <linux/config.h>
@@ -32,6 +37,7 @@
 #include <linux/slab.h>
 #include <linux/kbd_kern.h>
 #include <linux/smp_lock.h>
+#include <linux/module.h>
 
 #include <asm/keyboard.h>
 #include <asm/bitops.h>
@@ -60,6 +66,7 @@
 
 static void kbd_write_command_w(int data);
 static void kbd_write_output_w(int data);
+static void kb_wait(void);
 #ifdef CONFIG_PSMOUSE
 static void aux_write_ack(int val);
 static void __aux_write_ack(int val);
@@ -68,7 +75,7 @@
 static spinlock_t kbd_controller_lock = SPIN_LOCK_UNLOCKED;
 static unsigned char handle_kbd_event(void);
 
-/* used only by send_data - set by keyboard_interrupt */
+/* used by send_data and send_data_buffer - set by keyboard_interrupt */
 static volatile unsigned char reply_expected;
 static volatile unsigned char acknowledge;
 static volatile unsigned char resend;
@@ -94,6 +101,104 @@
 #define MAX_RETRIES	60		/* some aux operations take long time*/
 #endif /* CONFIG_PSMOUSE */
 
+#ifdef CONFIG_PC_KEYB_FILTER
+/* Use an array (instead of a linked list) to save time in_interrupt() */
+static struct pc_keyb_filter *filters[PC_KEYB_MAX_FILTERS];
+static int num_filters = 0;
+
+static DECLARE_MUTEX(kbd_output_sema);
+static spinlock_t pc_keyb_filter_lock = SPIN_LOCK_UNLOCKED;
+
+static int send_data_buffer( unsigned char *buffer, unsigned int len, unsigned int *xferred, unsigned int retries, unsigned int timeout )
+{
+	const unsigned int timeout_jiffies = ( (timeout * HZ) + 999 ) / 1000;
+	int i;
+	unsigned int xfer = 0;
+
+	if (xferred) *xferred = 0;
+
+	if (down_interruptible(&kbd_output_sema))
+		return -EINTR;
+	for (i=0; i<len; i++) {
+		do {
+			timeout = timeout_jiffies;
+			acknowledge = resend = 0;
+			reply_expected = 1;
+			kbd_write_output_w( (int)buffer[i] );
+			while (timeout-- && !resend && !acknowledge) {
+				set_current_state(TASK_INTERRUPTIBLE);
+				if (schedule_timeout(1) && signal_pending(current)) {
+					set_current_state(TASK_RUNNING);
+					up(&kbd_output_sema);
+					return -EINTR;
+				}
+				set_current_state(TASK_RUNNING);
+			}
+#ifdef KBD_REPORT_TIMEOUTS
+			if (0 >= timeout)
+				printk( __FILE__ ": Timeout - AT keyboard not present?\n" );
+#endif
+		} while (retries-- && !acknowledge && resend);
+		if (acknowledge) {
+			xfer++;
+			if (xferred) *xferred = xfer;
+		} else {
+#ifdef KBD_REPORT_TIMEOUTS
+			if (resend)
+				printk( __FILE__ ": Too many NACKs - Noisy keyboard cable?\n" );
+#endif
+			break;
+		}
+	}
+	up(&kbd_output_sema);
+
+	return len == xfer ? 0 : -ETIMEDOUT;
+}
+#endif /* CONFIG_PC_KEYB_FILTER */
+
+int register_pc_keyb_filter( struct pc_keyb_filter *filter )
+{
+#ifdef CONFIG_PC_KEYB_FILTER
+	unsigned long flags;
+	int retval = 0;
+
+	spin_lock_irqsave(&pc_keyb_filter_lock, flags);
+	if (PC_KEYB_MAX_FILTERS > num_filters) {
+		filters[num_filters++] = filter;
+		filter->write_data = send_data_buffer;
+	} else {
+		retval = -EDQUOT;
+	}
+	spin_unlock_irqrestore(&pc_keyb_filter_lock, flags);
+	return retval;
+#else
+	return -ENOSYS;
+#endif
+}
+
+void unregister_pc_keyb_filter( struct pc_keyb_filter *filter )
+{
+#ifdef CONFIG_PC_KEYB_FILTER
+	unsigned long flags;
+	int i, found = 0;
+
+	spin_lock_irqsave(&pc_keyb_filter_lock, flags);
+	filter->write_data = NULL;
+	for (i=0; i<num_filters; i++) {
+		if (filters[i] == filter)
+			found = 1;
+		if (found && i+1<PC_KEYB_MAX_FILTERS)
+			filters[i] = filters[i+1];
+	}
+	if (found)
+		filters[num_filters--] = NULL;
+	spin_unlock_irqrestore(&pc_keyb_filter_lock, flags);
+#endif
+}
+
+EXPORT_SYMBOL(register_pc_keyb_filter);
+EXPORT_SYMBOL(unregister_pc_keyb_filter);
+
 /*
  * Wait for keyboard controller input buffer to drain.
  *
@@ -428,6 +533,18 @@
 
 static inline void handle_keyboard_event(unsigned char scancode)
 {
+#ifdef CONFIG_PC_KEYB_FILTER
+	int i;
+
+	spin_lock(&pc_keyb_filter_lock);
+	for (i=0; i<num_filters; i++) {
+		if (filters[i]->filter_scancode( &scancode )) {
+			spin_unlock(&pc_keyb_filter_lock);
+			return;
+		}
+	}
+	spin_unlock(&pc_keyb_filter_lock);
+#endif /* CONFIG_PC_KEYB_FILTER */
 #ifdef CONFIG_VT
 	kbd_exists = 1;
 	if (do_acknowledge(scancode))
@@ -527,10 +644,17 @@
 
 void pckbd_leds(unsigned char leds)
 {
+#ifdef CONFIG_PC_KEYB_FILTER
+	if (down_interruptible(&kbd_output_sema))
+		return;
+#endif
 	if (kbd_exists && (!send_data(KBD_CMD_SET_LEDS) || !send_data(leds))) {
 		send_data(KBD_CMD_ENABLE);	/* re-enable kbd if any errors */
 		kbd_exists = 0;
 	}
+#ifdef CONFIG_PC_KEYB_FILTER
+	up(&kbd_output_sema);
+#endif
 }
 
 /*
diff -urN 2.4.5-clean/include/linux/pc_keyb.h linux/include/linux/pc_keyb.h
--- 2.4.5-clean/include/linux/pc_keyb.h	Mon Oct 11 13:15:40 1999
+++ linux/include/linux/pc_keyb.h	Fri Jun 15 13:34:18 2001
@@ -6,6 +6,11 @@
  *	(c) 1997 Martin Mares <mj@atrey.karlin.mff.cuni.cz>
  */
 
+#ifndef __PC_KEYB_H
+#define __PC_KEYB_H
+
+#ifdef __KERNEL__
+
 /*
  *	Configuration Switches
  */
@@ -128,3 +133,17 @@
 	struct fasync_struct *fasync;
 	unsigned char buf[AUX_BUF_SIZE];
 };
+
+#define PC_KEYB_MAX_FILTERS		1
+
+struct pc_keyb_filter {
+	int (*filter_scancode)( unsigned char *scancode );
+	int (*write_data)( unsigned char *data, unsigned int length, unsigned int *xferred, unsigned int retries, unsigned int timeout );
+};
+
+int register_pc_keyb_filter( struct pc_keyb_filter *filter );
+void unregister_pc_keyb_filter( struct pc_keyb_filter *filter );
+
+#endif /* __KERNEL__ */
+
+#endif /* __PC_KEYB_H */