[PATCH] Input: synaptics - Add LEN205b entry to smbus_pnp_ids for ThinkPad T490

[PATCH] Input: synaptics - Add LEN205b entry to smbus_pnp_ids for ThinkPad T490

[Lovekesh Solanki]

Lenovo ThinkPad T490 has a Synaptics Touchpad that supports SMBus/RMI4
mode, but is not listed in smbus_pnp_ids table.

Add LEN205b to smbus_pnp_ids[] passlist.

Reported-by: John Rosencutter <rosencutter@gmail.com>
Closes: https://lore.kernel.org/all/CAOGuaRh025eKcBf9P8UrvtXNp68vQ0HVF2EbNMp-kpdaC1HNpA@mail.gmail.com/
Signed-off-by: Lovekesh Solanki <lovekeshsolanki00@gmail.com>
---
 drivers/input/mouse/synaptics.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/input/mouse/synaptics.c b/drivers/input/mouse/synaptics.c
index 2170bbe4c589..14484164f067 100644
--- a/drivers/input/mouse/synaptics.c
+++ b/drivers/input/mouse/synaptics.c
@@ -192,6 +192,7 @@ static const char * const smbus_pnp_ids[] = {
 	"LEN2054", /* E480 */
 	"LEN2055", /* E580 */
 	"LEN2058", /* E490 */
+	"LEN205b", /* T490 */
 	"LEN2068", /* T14 Gen 1 */
 	"SYN1221", /* TUXEDO InfinityBook Pro 14 v5 */
 	"SYN3003", /* HP EliteBook 850 G1 */
-- 
2.55.0

Re: [PATCH] Input: synaptics - Add LEN205b entry to smbus_pnp_ids for ThinkPad T490

[Dmitry Torokhov]

On Mon, Sep 21, 2026 at 01:37:30AM +0530, Lovekesh Solanki wrote:
> Lenovo ThinkPad T490 has a Synaptics Touchpad that supports SMBus/RMI4
> mode, but is not listed in smbus_pnp_ids table.
> 
> Add LEN205b to smbus_pnp_ids[] passlist.
> 
> Reported-by: John Rosencutter <rosencutter@gmail.com>
> Closes: https://lore.kernel.org/all/CAOGuaRh025eKcBf9P8UrvtXNp68vQ0HVF2EbNMp-kpdaC1HNpA@mail.gmail.com/
> Signed-off-by: Lovekesh Solanki <lovekeshsolanki00@gmail.com>

Applied, thank you.

-- 
Dmitry

Re: [PATCH] Input: synaptics - Add LEN205b entry to smbus_pnp_ids for ThinkPad T490

[Jakariya Abbas]

Hi Lovekesh and Dmitry,

I have a ThinkPad T490 with the same Synaptics TM3471-020 touchpad
(LEN205B, firmware ID 3972349).
After the SMBus/RMI4 support was added, I noticed that touchpad
movement and scrolling work, but physical clicking and tapping become
extremely unreliable. A click registers only after several attempts.

My environment:
- ThinkPad T490
- Synaptics TM3471-020
- Tested on kernel 6.18.58-1-lts and 7.3.0-4-cachyos

Relevant kernel error:
    rmi4_physical rmi4-00: rmi_driver_clear_irq_bits:
    Failed to change enabled interrupts!

Workaround confirmed: Disabling Synaptics InterTouch resolves the
clicking and tapping issue:
    sudo modprobe -r psmouse
    sudo modprobe psmouse synaptics_intertouch=0

With this setting, the touchpad falls back to the PS/2 Synaptics path,
and clicking and tapping become reliable.
Could this indicate an issue with the SMBus/RMI4 implementation or
interrupt handling for this particular touchpad?
I would appreciate your guidance on whether this is an expected
limitation or a driver issue that needs further investigation.

Thank you.

Best Regards,
Jakariya Abbas

Re: [PATCH] Input: synaptics - Add LEN205b entry to smbus_pnp_ids for ThinkPad T490

[Lovekesh Solanki]

Hi Jakariya,

On Sat, Nov 07, 2026 at 12:16:29PM +0600, Jakariya Abbas wrote:
> Hi Lovekesh and Dmitry,
> 
> I have a ThinkPad T490 with the same Synaptics TM3471-020 touchpad
> (LEN205B, firmware ID 3972349).
> After the SMBus/RMI4 support was added, I noticed that touchpad
> movement and scrolling work, but physical clicking and tapping become
> extremely unreliable. A click registers only after several attempts.

Could you verify again whether this bug is really there, on mainline?
Because same issue was reported a week ago but then reporter said they
were unable to reproduce it.

...For some reason I can't find their mail on lore here's the link
to thread anyways.
https://lore.kernel.org/all/audS8Nb1wnifhCpr@eggarch/T/#u

Regards,
Lovekesh