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Subject/dev/psaux-caused kbd lockups and init problems fixed -- please test!

A few weeks ago, I ran out of serial ports, and since my motherboard
(Triton chipset) has a built-in PS/2 port, I decided to move the mouse
from a serial to the psaux port. Everything ok so far under M$DOS (so
I assumed the hardware itself being ok...), but under Linux, sometimes
strange keyboard lockups occured :-( More specifically, these lockups
happened sometimes when switching from X to a VC, or vice versa.

I traced the problem down to be a race when /dev/psaux is opened. The
driver then sends some multi-byte command sequences to the mouse (via
the kbd controller), and if a keyboard interrupt happens inside such a
sequence (in my case, the break code for Alt or Ctrl of A-Fx or
C-A-Fx), the trouble is there: keyboard_interrupt() itself sends a
command to the controller (0xad, to disable the kbd, later 0xae to
reenable it), and this mangling of different commands seems to confuse
the controller. It doesn't generate any interrupts anymore after
that...

My solution to the problem was to temporarily disable the keyboard
(with the 0xad command) while sending such multi-byte sequences to the
mouse. Finally, this has fixed the lockup problems. BTW, such
sequences are not only in open_aux(), but also in two other places. I
did the same fix there, too.

But then I noticed something else: Since my notebook (Mitac 4023, i.e.
no-name :-), trackball acting as PS/2 mouse) needs the psaux device to
be initialized (#define INITIALIZE_DEVICE in psaux.c), I also compiled
a kernel with that initialization included. And, everytime after
booting, the mouse was dead :-( It worked again after closing and
re-opening /dev/psaux (i.e., by switching from X to VC or the other
way round). Some more debugging showed that the driver obviously sent
commands too fast to the mouse, and it responded with RESEND requests,
that the driver silently ignored. Consequence was that the mouse was
totally misconfigured.

To fix this, I additionally changed the init procedure to 1) wait for
the ACKs from the mouse/controller and 2) to handle such RESEND
requests. Already 1) alone solved the "too-fast" problem :-), but it
seems safer to keep the RESEND handling code, in case it should be
needed. (I also provoked RESEND to test the code... :-)

And, since I was already hacking around in psaux.c, I made some more
cleanups...

Ok, a summary of the changes I made:

- The keyboard is disabled for each critical section where multi-byte
command sequences are sent, to avoid confusion in the controller
between commands/data for the mouse and kbd commands given in
kbd_intr(). Those critical sections are in: release_aux(),
aux_open(), and write_aux() (user commands). I've always taken care
to not leave the keyboard disabled if any errors happen.

- poll_aux_status_nosleep() isn't needed anymore, since 1.3.24 driver
init functions can sleep, too.

- New function aux_write_byte() for writing to controller and wait
for input buffer being free again. (similar to send_cmd() in
keyboard.c)

- aux_write_dev() (without checking for ACK) not needed anymore,
every aux device command (except RESET, which isn't used) returns
an ACK. Instead, aux_write_ack() now always needed, not only if
INITIALIZE_DEVICE is defined.

- aux_write_ack() now really waits for the ACK being returned from
the mouse. Formerly it just waited as long as the input buffer was
full, which is usually not long enough.

- aux_write_ack() also handles RESEND requests. If it receives RESEND
(0xfa) instead of ACK (0xfe), it sends the byte for the mouse
again.

- poll_aux_status() not just empties the output buffer, but also
returns what it has read. Necessary for checking for ACK and
RESEND. With this, the return values' semantics have changed: < 0
means timeout, 0 means ok, > 0 is a byte received from the device.

- Better error checking (timeouts) in all functions.

- init_module() is quite ok, cry for help is outdated... :-)

You see, quit a lot of stuff, and I admit that I can't guarantee that
it doesn't break /dev/psaux on some other machine... No need to say
that it works well on both my machines, the desktop and the notebook.
But, obviously, a much broader test is needed... (I've already
contacted Alessandro Rubini, the mouse maintainer, but he didn't know
any testers, too :-( )

So: If you're using a PS/2 mouse, or had problems with it in the past,
please test the patch below and tell me about results! Please reply to
me directly, not to this mailing list, since I'm not subscribed here
(jusst too much traffic... I know better ways for keeping me busy :-)

Roman

PS: The patch is relative to 2.0, but psaux.c hasn't changed for quite
a long time now, and it should apply to all not too old kernel
versions.

---------------------------------------------------------------------------

--- linux-2.0/driver/char/psaux.c~ Fri Jun 21 19:23:56 1996
+++ linux-2.0/driver/char/psaux.c Wed Jul 3 21:10:00 1996
@@ -25,6 +25,10 @@
* Rearranged SIGIO support to use code from tty_io. 9Sept95 ctm@ardi.com
*
* Modularised 8-Sep-95 Philip Blundell <pjb27@cam.ac.uk>
+ *
+ * Fixed keyboard lockups at open time (intervening kbd interrupts), handle
+ * RESEND replies, better error checking
+ * 3-Jul-96 Roman Hodek <Roman.Hodek@informatik.uni-erlangen.de>
*/

/* Uncomment the following line if your mouse needs initialization. */
@@ -57,8 +61,10 @@
#define AUX_STATUS 0x64 /* Aux device status reg */

/* aux controller status bits */
+#define AUX_KOBUF_FULL 0x01 /* output buffer (from controller) full */
#define AUX_OBUF_FULL 0x21 /* output buffer (from device) full */
#define AUX_IBUF_FULL 0x02 /* input buffer (to device) full */
+#define AUX_TIMEOUT 0x40 /* controller reports timeout */

/* aux controller commands */
#define AUX_CMD_WRITE 0x60 /* value to write to controller */
@@ -81,6 +87,14 @@
#define AUX_DISABLE_DEV 0xf5 /* disable aux device */
#define AUX_RESET 0xff /* reset aux device */

+/* kbd controller commands */
+#define KBD_DISABLE 0xad
+#define KBD_ENABLE 0xae
+
+/* replies */
+#define AUX_ACK 0xfa
+#define AUX_RESEND 0xfe
+
#define MAX_RETRIES 60 /* some aux operations take long time*/
#if defined(__alpha__) && !defined(CONFIG_PCI)
# define AUX_IRQ 9 /* Jensen is odd indeed */
@@ -121,7 +135,6 @@
static int aux_count = 0;
static int aux_present = 0;
static int poll_aux_status(void);
-static int poll_aux_status_nosleep(void);
static int fasync_aux(struct inode *inode, struct file *filp, int on);

#ifdef CONFIG_82C710_MOUSE
@@ -136,49 +149,70 @@


/*
- * Write to aux device
+ * Write a byte to the kbd controller and wait for it being processed
*/

-static void aux_write_dev(int val)
+static int aux_write_byte(int val,int port)
{
- poll_aux_status();
- outb_p(AUX_MAGIC_WRITE,AUX_COMMAND); /* write magic cookie */
- poll_aux_status();
- outb_p(val,AUX_OUTPUT_PORT); /* write data */
+ outb_p(val, port);
+ return poll_aux_status();
}

/*
- * Write to device & handle returned ack
+ * Write to device, handle returned resend requests and wait for ack
*/
-#if defined INITIALIZE_DEVICE
static int aux_write_ack(int val)
{
- int retries = 0;
+ int rv, retries = 0, stat;

- poll_aux_status_nosleep();
- outb_p(AUX_MAGIC_WRITE,AUX_COMMAND);
- poll_aux_status_nosleep();
- outb_p(val,AUX_OUTPUT_PORT);
- poll_aux_status_nosleep();
-
- if ((inb(AUX_STATUS) & AUX_OBUF_FULL) == AUX_OBUF_FULL)
- {
- return (inb(AUX_INPUT_PORT));
+ repeat:
+ if (poll_aux_status() < 0)
+ return -1;
+ outb_p(AUX_MAGIC_WRITE, AUX_COMMAND);
+ if (poll_aux_status() < 0)
+ return -1;
+ outb_p(val, AUX_OUTPUT_PORT);
+
+ if ((rv = poll_aux_status()) < 0)
+ /* timeout */
+ return -1;
+ else if (rv == AUX_RESEND)
+ /* controller needs last byte again... */
+ goto repeat;
+ else if (rv == AUX_ACK)
+ /* already got ACK */
+ return 0;
+ else {
+ /* wait for ACK from controller */
+ while (retries < MAX_RETRIES) {
+ stat = inb_p(AUX_STATUS);
+ if ((stat & AUX_OBUF_FULL) == AUX_OBUF_FULL &&
+ inb_p(AUX_INPUT_PORT) == AUX_ACK)
+ return 0;
+ current->state = TASK_INTERRUPTIBLE;
+ current->timeout = jiffies + (5*HZ + 99) / 100;
+ schedule();
+ retries++;
+ }
+ return -1;
}
- return 0;
}
-#endif /* INITIALIZE_DEVICE */

/*
* Write aux device command
*/

-static void aux_write_cmd(int val)
+static int aux_write_cmd(int val)
{
- poll_aux_status();
- outb_p(AUX_CMD_WRITE,AUX_COMMAND);
- poll_aux_status();
- outb_p(val,AUX_OUTPUT_PORT);
+ if (poll_aux_status() < 0)
+ return -1;
+ outb_p(AUX_CMD_WRITE, AUX_COMMAND);
+ if (poll_aux_status() < 0)
+ return -1;
+ outb_p(val, AUX_OUTPUT_PORT);
+ if (poll_aux_status() < 0)
+ return -1;
+ return 0;
}


@@ -258,10 +292,19 @@
fasync_aux(inode, file, 0);
if (--aux_count)
return;
- aux_write_cmd(AUX_INTS_OFF); /* disable controller ints */
- poll_aux_status();
- outb_p(AUX_DISABLE,AUX_COMMAND); /* Disable Aux device */
+ /* disable keyboard to avoid clashes with multi-byte command sequences */
poll_aux_status();
+ if (aux_write_byte(KBD_DISABLE, AUX_COMMAND) < 0)
+ printk(KERN_ERR "psaux: controller timeout\n");
+ /* disable controller ints */
+ if (aux_write_cmd(AUX_INTS_OFF) < 0)
+ printk(KERN_ERR "psaux: controller timeout\n");
+ /* Disable Aux device */
+ if (aux_write_byte(AUX_DISABLE, AUX_COMMAND) < 0)
+ printk(KERN_ERR "psaux: controller timeout\n");
+ /* re-enable keyboard */
+ if (aux_write_byte(KBD_ENABLE, AUX_COMMAND) < 0)
+ printk(KERN_ERR "psaux: controller timeout\n");
free_irq(AUX_IRQ, NULL);
MOD_DEC_USE_COUNT;
}
@@ -306,7 +349,7 @@
return -ENODEV;
if (aux_count++)
return 0;
- if (!poll_aux_status()) {
+ if (poll_aux_status() < 0) {
aux_count--;
return -EBUSY;
}
@@ -317,12 +360,27 @@
}
MOD_INC_USE_COUNT;
poll_aux_status();
- outb_p(AUX_ENABLE,AUX_COMMAND); /* Enable Aux */
- aux_write_dev(AUX_ENABLE_DEV); /* enable aux device */
- aux_write_cmd(AUX_INTS_ON); /* enable controller ints */
- poll_aux_status();
+ /* disable keyboard to avoid clashes with multi-byte command sequences */
+ if (aux_write_byte(KBD_DISABLE, AUX_COMMAND) < 0)
+ goto open_error;
+ /* Enable Aux in kbd controller */
+ if (aux_write_byte(AUX_ENABLE, AUX_COMMAND) < 0)
+ goto open_error;
+ /* enable aux device */
+ if (aux_write_ack(AUX_ENABLE_DEV) < 0)
+ goto open_error;
+ /* enable controller ints */
+ if (aux_write_cmd(AUX_INTS_ON) < 0)
+ goto open_error;
+ /* re-enable keyboard */
+ if (aux_write_byte(KBD_ENABLE, AUX_COMMAND) < 0)
+ goto open_error;
+
aux_ready = 0;
return 0;
+ open_error:
+ printk( KERN_ERR "psaux: controller timeout\n" );
+ return -EIO;
}

#ifdef CONFIG_82C710_MOUSE
@@ -378,17 +436,31 @@
static int write_aux(struct inode * inode, struct file * file, const char * buffer, int count)
{
int i = count;
+ int rv = 0;
+
+ /* temporary disable keyboard to avoid clashes with multi-byte command
+ * sequence */
+ if (aux_write_byte(KBD_DISABLE, AUX_COMMAND) < 0)
+ return -EIO;

while (i--) {
- if (!poll_aux_status())
- return -EIO;
+ if (poll_aux_status() < 0) {
+ rv = -EIO;
+ break;
+ }
outb_p(AUX_MAGIC_WRITE,AUX_COMMAND);
- if (!poll_aux_status())
- return -EIO;
+ if (poll_aux_status() < 0) {
+ rv = -EIO;
+ break;
+ }
outb_p(get_user(buffer++),AUX_OUTPUT_PORT);
}
+ /* reenable keyboard */
+ if (poll_aux_status() < 0 || aux_write_byte(KBD_ENABLE, AUX_COMMAND) < 0)
+ rv = -EIO;
+
inode->i_mtime = CURRENT_TIME;
- return count;
+ return rv ? rv : count;
}


@@ -519,13 +591,11 @@
aux_write_ack(AUX_SET_RES);
aux_write_ack(3); /* 8 counts per mm */
aux_write_ack(AUX_SET_SCALE21); /* 2:1 scaling */
- poll_aux_status_nosleep();
#endif /* INITIALIZE_DEVICE */
- outb_p(AUX_DISABLE,AUX_COMMAND); /* Disable Aux device */
- poll_aux_status_nosleep();
- outb_p(AUX_CMD_WRITE,AUX_COMMAND);
- poll_aux_status_nosleep(); /* Disable interrupts */
- outb_p(AUX_INTS_OFF, AUX_OUTPUT_PORT); /* on the controller */
+ /* Disable Aux device and its interrupts on the controller */
+ if (aux_write_byte(AUX_DISABLE, AUX_COMMAND) < 0 ||
+ aux_write_cmd(AUX_INTS_OFF) < 0)
+ printk(KERN_ERR "psaux: controller timeout\n");
}
return 0;
}
@@ -533,7 +603,7 @@
#ifdef MODULE
int init_module(void)
{
- return psaux_init(); /*?? Bjorn */
+ return psaux_init();
}

void cleanup_module(void)
@@ -545,28 +615,18 @@
static int poll_aux_status(void)
{
int retries=0;
+ int reply=0;

- while ((inb(AUX_STATUS)&0x03) && retries < MAX_RETRIES) {
+ while ((inb(AUX_STATUS) & (AUX_KOBUF_FULL|AUX_IBUF_FULL)) &&
+ retries < MAX_RETRIES) {
if ((inb_p(AUX_STATUS) & AUX_OBUF_FULL) == AUX_OBUF_FULL)
- inb_p(AUX_INPUT_PORT);
+ reply = inb_p(AUX_INPUT_PORT);
current->state = TASK_INTERRUPTIBLE;
current->timeout = jiffies + (5*HZ + 99) / 100;
schedule();
retries++;
}
- return !(retries==MAX_RETRIES);
-}
-
-static int poll_aux_status_nosleep(void)
-{
- int retries = 0;
-
- while ((inb(AUX_STATUS)&0x03) && retries < 1000000) {
- if ((inb_p(AUX_STATUS) & AUX_OBUF_FULL) == AUX_OBUF_FULL)
- inb_p(AUX_INPUT_PORT);
- retries++;
- }
- return !(retries == 1000000);
+ return (retries==MAX_RETRIES) ? -1 : reply;
}

#ifdef CONFIG_82C710_MOUSE

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