[PATCH] Input: psmouse - further improve error handling forbasic protocols

[Jim Hill]

  Keep a failing PS/2 mouse usable until it's convenient to replace it.
  Filter incoming packets: drop invalid ones and attempt to correct for
  dropped bytes.
 
  New parameter 'filter' makes filtering and logging selectable, leave at 0
  to shut off all effects, 3 to work silently.
--
 drivers/input/mouse/psmouse-base.c | 197 +++++++++++++++++++++++++++++++++++++
 drivers/input/mouse/psmouse.h      |   7 ++
 2 files changed, 204 insertions(+)

diff --git a/drivers/input/mouse/psmouse-base.c b/drivers/input/mous/psmouse-base.c
index 22fe254..4a3a95f 100644
--- a/drivers/input/mouse/psmouse-base.c
+++ b/drivers/input/mouse/psmouse-base.c
@@ -72,6 +72,25 @@ static unsigned int psmouse_resync_time;
 module_param_named(resync_time, psmouse_resync_time, uint, 0644);
 MODULE_PARM_DESC(resync_time, "How long can mouse stay idle before forcing resync (in seconds, 0 = never).");

+enum {
+	DROP_BAD_PACKET = 1,
+	ATTEMPT_SYNC = 2,
+	LOG_SUMMARIES = 4,
+	LOG_MALFORMED = 8,
+	LOG_ALL	 = 16,
+	REPORT_SYNC_FAILURE = 32,
+
+	DEFAULT_FILTER = 0
+};
+static int psmouse_filter = DEFAULT_FILTER;
+module_param_named(filter, psmouse_filter, int, 0644);
+MODULE_PARM_DESC(filter, "1 = drop invalid or hotio packets"
+		", +2 = attempt-sync"
+		", +4 = summary logs"
+		", +8 = log-malformed"
+		",+16 = log-all"
+		",+32 = use hard resets");
+
 PSMOUSE_DEFINE_ATTR(protocol, S_IWUSR | S_IRUGO,
 			NULL,
 			psmouse_attr_show_protocol, psmouse_attr_set_protocol);
@@ -123,6 +142,169 @@ struct psmouse_protocol {
 };

 /*
+ * psmouse_filter_*: diagnose bad data, recover what we can, drop the rest, log
+ * selected events. See input_report_*()s in psmouse_process_byte below, and
+ * <http://www.computer-engineering.org/ps2mouse/>
+ */
+
+static int psmouse_filter_header_byte(enum psmouse_type type, int byte)
+{
+	int todo = 0;
+	if ((byte & 0xc0) &&
+			type != PSMOUSE_THINKPS &&
+			type != PSMOUSE_GENPS)
+		todo |= DROP_BAD_PACKET+ATTEMPT_SYNC;
+	if ((byte & 0x08) == 0 &&
+			type != PSMOUSE_THINKPS &&
+			type != PSMOUSE_CORTRON)
+		todo |= DROP_BAD_PACKET+ATTEMPT_SYNC;
+	return todo;
+}
+
+static int psmouse_filter_wheel_byte(enum psmouse_type type, int byte)
+{
+	int todo = 0;
+	if (type == PSMOUSE_IMPS || type == PSMOUSE_GENPS)
+		if (abs(byte) > 3)
+			todo = DROP_BAD_PACKET+ATTEMPT_SYNC;
+	if (type == PSMOUSE_IMEX)
+		if (((byte&0xC0) == 0) || ((byte&0XC0) == 0xC0))
+			if (abs((byte&0x08)-(byte&0x07)) > 3)
+				todo = DROP_BAD_PACKET+ATTEMPT_SYNC;
+	return todo;
+}
+
+static int psmouse_filter_motion(struct psmouse *m)
+{	/*
+	 * Hunt for implausible accelerations here if it ever seems necessary.
+	 * Header/wheel sniffing seems to detect everything recoverable so far.
+	 */
+	return 0;
+}
+
+static int psmouse_filter_hotio(struct psmouse *m)
+{
+	int ret = 0;
+	if (time_after(m->last, m->hotio_interval_start + HZ/m->rate)) {
+		m->hotio_interval_pkts = 0;
+		m->hotio_interval_start = m->last;
+	}
+	if (m->hotio_interval_pkts++ > m->rate/HZ + 1) {
+		if (m->hotio_log_counter == 0)
+			m->hotio_log_interval_start = m->last;
+		++m->hotio_log_counter;
+		ret = DROP_BAD_PACKET;
+	}
+	return ret;
+}
+
+static void psmouse_filter_packet_logger(struct psmouse *m, int todo,
+		const char *tag)
+{
+	if ((todo & psmouse_filter & LOG_MALFORMED) ||
+			(psmouse_filter & LOG_ALL)) {
+		unsigned long long packet = 0;
+		int p;
+		for (p = 0; p < m->pktcnt; ++p)
+			packet = packet<<8 | m->packet[p];
+		printk(KERN_INFO "psmouse.c: packet %0*llx%s\n", p*2, packet,
+			tag ? tag : "");
+	}
+}
+
+static int psmouse_filter_inspect_packet(struct psmouse *m)
+{
+	int todo = 0;
+	todo |= psmouse_filter_header_byte(m->type, m->packet[0]);
+	todo |= psmouse_filter_motion(m);
+	todo |= psmouse_filter_wheel_byte(m->type, (signed char)m->packet[3]);
+	if (todo & DROP_BAD_PACKET) {
+		todo |= LOG_MALFORMED;
+		if (m->err_log_counter == 0)
+			m->err_log_interval_start = m->last;
+		++m->err_log_counter;
+	}
+	return todo;
+}
+
+/*
+ * find-sync: if the mouse dropped one or more bytes the next packet start
+ * byte's almost certainly in this buffer. Return its offset if we can find it.
+ */
+static unsigned psmouse_filter_find_sync(struct psmouse *m)
+{
+	int p;
+
+	/* same buttons, same general direction as last report? Seems best */
+	for (p = m->pktcnt; --p ; )
+		if (m->packet[p] == m->last_good_packet[0])
+			return p;
+
+	/* same or no buttons, plausible direction from what we can see? */
+	for (p = m->pktcnt; --p ; ) {
+		signed char test0 = (signed char)m->packet[p];
+		signed char last0 = (signed char)m->last_good_packet[0];
+		signed char test1 = (signed char)m->packet[(p+1)%m->pktcnt];
+		signed char test2 = (signed char)m->packet[(p+2)%m->pktcnt];
+		if (((test0&7) == 0 || (test0&7) == (last0&7)) &&
+				(test0>>4&1) == (test1>>7&1) &&
+				(test0>>5&1) == (test2>>7&1) &&
+				!psmouse_filter_header_byte(m->type, test0))
+			return p;
+	}
+	/* nothing looks good */
+	return 0;
+}
+
+static void psmouse_filter_write_summary_logs(struct psmouse *m)
+{
+	if (m->err_log_counter && time_after(m->last, m->err_log_interval_start+HZ)) {
+		printk(KERN_WARNING "psmouse.c: %s at %s %lu bad packets\n",
+				m->name, m->phys, m->err_log_counter);
+		m->err_log_counter = m->err_log_interval_start = 0;
+	}
+	if (m->hotio_log_counter && time_after(m->last, m->hotio_log_interval_start+HZ)) {
+		printk(KERN_WARNING "psmouse.c: %s at %s %lu excess packets\n",
+				m->name, m->phys, m->hotio_log_counter);
+		m->hotio_log_counter = m->hotio_log_interval_start = 0;
+	}
+}
+
+static int psmouse_filter_packet(struct psmouse *m)
+{
+	int todo;
+
+	if (psmouse_filter < 0)
+		psmouse_filter = DEFAULT_FILTER;
+
+	todo = psmouse_filter_inspect_packet(m);
+
+	if (!(todo & DROP_BAD_PACKET))
+		todo |= psmouse_filter_hotio(m);
+
+	psmouse_filter_packet_logger(m, todo, todo&LOG_MALFORMED ? " bad" : 0);
+	if (psmouse_filter & (LOG_SUMMARIES | LOG_ALL))
+		psmouse_filter_write_summary_logs(m);
+
+	if (todo & psmouse_filter & ATTEMPT_SYNC) {
+		unsigned p = psmouse_filter_find_sync(m);
+		if (p) {
+			m->pktcnt -= p;
+			memmove(m->packet, m->packet+p, m->pktcnt);
+			psmouse_filter_packet_logger(m, todo, " sync");
+		} else {
+			todo |= REPORT_SYNC_FAILURE;
+			todo &= ~ATTEMPT_SYNC;
+		}
+	}
+
+	if (!(todo & DROP_BAD_PACKET))
+		memcpy(m->last_good_packet, m->packet, sizeof m->packet);
+
+	return todo & psmouse_filter;
+}
+
+/*
  * psmouse_process_byte() analyzes the PS/2 data stream and reports
  * relevant events to the input module once full packet has arrived.
  */
@@ -135,6 +317,15 @@ psmouse_ret_t psmouse_process_byte(struct psmouse *psmouse)
 	if (psmouse->pktcnt < psmouse->pktsize)
 		return PSMOUSE_GOOD_DATA;

+	{
+		int filter = psmouse_filter_packet(psmouse);
+		if (filter & ATTEMPT_SYNC)
+			return PSMOUSE_GOOD_DATA;
+		if (filter & REPORT_SYNC_FAILURE)
+			return PSMOUSE_BAD_DATA;
+		if (filter & DROP_BAD_PACKET)
+			return PSMOUSE_FULL_PACKET;
+	}
 /*
  * Full packet accumulated, process it
  */
@@ -226,6 +417,12 @@ static inline void __psmouse_set_state(struct psmouse *psmouse, enum psmouse_sta
 	psmouse->pktcnt = psmouse->out_of_sync_cnt = 0;
 	psmouse->ps2dev.flags = 0;
 	psmouse->last = jiffies;
+	psmouse->err_log_interval_start = 0;
+	psmouse->err_log_counter = 0;
+	psmouse->hotio_interval_start = 0;
+	psmouse->hotio_interval_pkts = 0;
+	psmouse->hotio_log_interval_start = 0;
+	psmouse->hotio_log_counter = 0;
 }


diff --git a/drivers/input/mouse/psmouse.h b/drivers/input/mouse/psmouse.h
index fe1df23..7d8817e7 100644
--- a/drivers/input/mouse/psmouse.h
+++ b/drivers/input/mouse/psmouse.h
@@ -44,6 +44,7 @@ struct psmouse {
 	char *vendor;
 	char *name;
 	unsigned char packet[8];
+	unsigned char last_good_packet[8];
 	unsigned char badbyte;
 	unsigned char pktcnt;
 	unsigned char pktsize;
@@ -54,6 +55,12 @@ struct psmouse {
 	unsigned long last;
 	unsigned long out_of_sync_cnt;
 	unsigned long num_resyncs;
+	unsigned long hotio_interval_start;
+	unsigned long hotio_interval_pkts;
+	unsigned long hotio_log_interval_start;
+	unsigned long hotio_log_counter;
+	unsigned long err_log_interval_start;
+	unsigned long err_log_counter;
 	enum psmouse_state state;
 	char devname[64];
 	char phys[32];
-- 
1.7.11.rc2.220.g2b5a256

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