[PATCH v2] Input: psmouse - fix fast_reconnect function for PS/2 mode

[PATCH v2] Input: psmouse - fix fast_reconnect function for PS/2 mode

[Jeffery Miller]

Make elantech_setup_ps2 and synaptics_init_ps2 set an appropriate
fast_reconnect pointer when the PS/2 mode is used.

When the SMBus connection is attempted psmouse_smbus_init sets
the fast_reconnect pointer to psmouse_smbus_reconnect. When this fails
elantech_setup_ps2 and synaptics_init_ps2 will fallback to PS/2
mode replacing the psmouse private data.
This was causing an issue on resume since psmouse_smbus_reconnect was
being called while in PS/2 mode and attempting to use the invalid
private data.

This issue was uncovered when psmouse_smbus_reconnect started attempting
to use more of the data structure.

Reported-by: Thorsten Leemhuis <linux@leemhuis.info>
Closes: https://lore.kernel.org/all/ca0109fa-c64b-43c1-a651-75b294d750a1@leemhuis.info/
Fixes: 92e24e0e57f7 ("Input: psmouse - add delay when deactivating for SMBus mode")

Tested-by: Thorsten Leemhuis <linux@leemhuis.info>

Signed-off-by: Jeffery Miller <jefferymiller@google.com>
---

The other callbacks set in psmouse_smbus_init are already replaced.


Changes in v2:
- Also set fast_reconnect in the synaptics ps2 fallback path from review
  comments.
- Add Fixes: tag to the commit that uncovered the problem.

 drivers/input/mouse/elantech.c  | 1 +
 drivers/input/mouse/synaptics.c | 1 +
 2 files changed, 2 insertions(+)

diff --git a/drivers/input/mouse/elantech.c b/drivers/input/mouse/elantech.c
index 2118b2075f43..4e38229404b4 100644
--- a/drivers/input/mouse/elantech.c
+++ b/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;
diff --git a/drivers/input/mouse/synaptics.c b/drivers/input/mouse/synaptics.c
index ada299ec5bba..cefc74b3b34b 100644
--- a/drivers/input/mouse/synaptics.c
+++ b/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;
-- 
2.42.0.582.g8ccd20d70d-goog

Re: [PATCH v2] Input: psmouse - fix fast_reconnect function for PS/2 mode

[Jeffery Miller]

On Wed, Oct 4, 2023 at 7:23 PM Jeffery Miller <jefferymiller@google.com> wrote:
>
>  drivers/input/mouse/elantech.c  | 1 +
>  drivers/input/mouse/synaptics.c | 1 +
>  2 files changed, 2 insertions(+)
>
> diff --git a/drivers/input/mouse/elantech.c b/drivers/input/mouse/elantech.c
> index 2118b2075f43..4e38229404b4 100644
> --- a/drivers/input/mouse/elantech.c
> +++ b/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;
> diff --git a/drivers/input/mouse/synaptics.c b/drivers/input/mouse/synaptics.c
> index ada299ec5bba..cefc74b3b34b 100644
> --- a/drivers/input/mouse/synaptics.c
> +++ b/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;
> --
> 2.42.0.582.g8ccd20d70d-goog
>

This fast_reconnect function pointer being left over has been here since commit
8eb92e5c9133 ("Input: psmouse - add support for SMBus companions")

It is only recently noticed due to 92e24e0e57f7 ("Input: psmouse - add
delay when deactivating for SMBus mode") which is in the v6.6 rc
branches.

Shouldn't it be OK to merge regardless of a future refactor of
8eb92e5c9133 ("Input: psmouse - add support for SMBus companions")
as described in https://lore.kernel.org/all/ZR1yUFJ8a9Zt606N@penguin/?

This is a v2 from the previous submission at
https://lore.kernel.org/all/20231004005729.3943515-1-jefferymiller@google.com/

Thanks,
Jeff