Input: psmouse - fix fast_reconnect function for PS/2 mode

When the SMBus connection is attempted psmouse_smbus_init() sets
the fast_reconnect pointer to psmouse_smbus_reconnecti(). If SMBus
initialization fails, elantech_setup_ps2() and synaptics_init_ps2() will
fallback to PS/2 mode, replacing the psmouse private data. This can cause
issues on resume, since psmouse_smbus_reconnect() expects to find an
instance of struct psmouse_smbus_dev in psmouse->private.

The issue was uncovered when in 92e24e0 ("Input: psmouse - add
delay when deactivating for SMBus mode") psmouse_smbus_reconnect()
started attempting to use more of the data structure. The commit was
since reverted, not because it was at fault, but because there was found
a better way of doing what it was attempting to do.

Fix the problem by resetting the fast_reconnect pointer in psmouse
structure in elantech_setup_ps2() and synaptics_init_ps2() when the PS/2
mode is used.

Reported-by: Thorsten Leemhuis <linux@leemhuis.info>
Tested-by: Thorsten Leemhuis <linux@leemhuis.info>
Signed-off-by: Jeffery Miller <jefferymiller@google.com>
Fixes: bf232e4 ("Input: psmouse-smbus - allow to control psmouse_deactivate")
Link: https://lore.kernel.org/r/20231005002249.554877-1-jefferymiller@google.com
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Author: jefferymiller

drivers/input/mouse/elantech.c

@@ -2114,6 +2114,7 @@ static int elantech_setup_ps2(struct psmouse *psmouse,
 	psmouse->protocol_handler = elantech_process_byte;
 	psmouse->disconnect = elantech_disconnect;
 	psmouse->reconnect = elantech_reconnect;
+	psmouse->fast_reconnect = NULL;
 	psmouse->pktsize = info->hw_version > 1 ? 6 : 4;
 
 	return 0;

drivers/input/mouse/synaptics.c

@@ -1623,6 +1623,7 @@ static int synaptics_init_ps2(struct psmouse *psmouse,
 	psmouse->set_rate = synaptics_set_rate;
 	psmouse->disconnect = synaptics_disconnect;
 	psmouse->reconnect = synaptics_reconnect;
+	psmouse->fast_reconnect = NULL;
 	psmouse->cleanup = synaptics_reset;
 	/* Synaptics can usually stay in sync without extra help */
 	psmouse->resync_time = 0;