Upon receiving a PS/2 command the device and controller are supposed to
stop sending normal data (scancodes or movement packets) and instead
immediately start delivering ACK/NAK and command response. Unfortunately
often EC has an output buffer which may contain latched data by the time
the EC receives a command from the host. The kernel used to ignore such
data, but that may cause "stuck" keys if the data dropped happens to be a
break code or a part of a break code. This occasionally happens, for
example, on Chromebooks when the kernel tries to toggle CapsLock LED on
a keyboard while user releases Alt+Search keyboard shortcut.
Fix this by passing the first non-ACK byte to the normal handler for a
handful of PS/2 commands that are expected to be used during normal device
operation (as opposed to probe/configuration time).
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>
---
drivers/input/serio/libps2.c | 36 ++++++++++++++++++++++++++++++++----
1 file changed, 32 insertions(+), 4 deletions(-)
diff --git a/drivers/input/serio/libps2.c b/drivers/input/serio/libps2.c
index 7c5fc853072a..6d78a1fe00c1 100644
--- a/drivers/input/serio/libps2.c
+++ b/drivers/input/serio/libps2.c
@@ -21,7 +21,10 @@
#define PS2_CMD_SETSCALE11 0x00e6
#define PS2_CMD_SETRES 0x10e8
+#define PS2_CMD_EX_SETLEDS 0x20eb
+#define PS2_CMD_SETLEDS 0x10ed
#define PS2_CMD_GETID 0x02f2
+#define PS2_CMD_SETREP 0x10f3 /* Set repeat rate/set report rate */
#define PS2_CMD_RESET_BAT 0x02ff
#define PS2_RET_BAT 0xaa
@@ -35,6 +38,7 @@
#define PS2_FLAG_CMD1 BIT(2) /* Waiting for the first byte of command response */
#define PS2_FLAG_WAITID BIT(3) /* Command executing is GET ID */
#define PS2_FLAG_NAK BIT(4) /* Last transmission was NAKed */
+#define PS2_FLAG_PASS_NOACK BIT(5) /* Pass non-ACK byte to receive handler */
static int ps2_do_sendbyte(struct ps2dev *ps2dev, u8 byte,
unsigned int timeout, unsigned int max_attempts)
@@ -281,9 +285,28 @@ int __ps2_command(struct ps2dev *ps2dev, u8 *param, unsigned int command)
serio_pause_rx(ps2dev->serio);
- /* Some mice do not ACK the "get ID" command, prepare to handle this. */
- ps2dev->flags = command == PS2_CMD_GETID ? PS2_FLAG_WAITID : 0;
ps2dev->cmdcnt = receive;
+
+ switch (command) {
+ case PS2_CMD_GETID:
+ /*
+ * Some mice do not ACK the "get ID" command, prepare to
+ * handle this.
+ */
+ ps2dev->flags = PS2_FLAG_WAITID;
+ break;
+
+ case PS2_CMD_SETLEDS:
+ case PS2_CMD_EX_SETLEDS:
+ case PS2_CMD_SETREP:
+ ps2dev->flags = PS2_FLAG_PASS_NOACK;
+ break;
+
+ default:
+ ps2dev->flags = 0;
+ break;
+ }
+
if (receive) {
/* Indicate that we expect response to the command. */
ps2dev->flags |= PS2_FLAG_CMD | PS2_FLAG_CMD1;
@@ -512,14 +535,19 @@ static void ps2_handle_ack(struct ps2dev *ps2dev, u8 data)
* Do not signal errors if we get unexpected reply while
* waiting for an ACK to the initial (first) command byte:
* the device might not be quiesced yet and continue
- * delivering data.
+ * delivering data. For certain commands (such as set leds and
+ * set repeat rate) that can be used during normal device
+ * operation, we even pass this data byte to the normal receive
+ * handler.
* Note that we reset PS2_FLAG_WAITID flag, so the workaround
* for mice not acknowledging the Get ID command only triggers
* on the 1st byte; if device spews data we really want to see
* a real ACK from it.
*/
dev_dbg(&ps2dev->serio->dev, "unexpected %#02x\n", data);
- ps2dev->flags &= ~PS2_FLAG_WAITID;
+ if (ps2dev->flags & PS2_FLAG_PASS_NOACK)
+ ps2dev->receive_handler(ps2dev, data);
+ ps2dev->flags &= ~(PS2_FLAG_WAITID | PS2_FLAG_PASS_NOACK);
return;
}
--
2.40.1.606.ga4b1b128d6-goog
