[PATCH] HID: logitech-hidpp: Silence protocol errors on newer lightspeed receivers

[PATCH] HID: logitech-hidpp: Silence protocol errors on newer lightspeed receivers

[Mavroudis Chatzilazaridis]

When logitech-hidpp tries to communicate with an unreachable device paired
to a 046d:c547 lightspeed receiver, the following message is printed to the
console:

hidpp_root_get_protocol_version: received protocol error 0x08

This occurs because this receiver returns 0x08 (HIDPP_ERROR_UNKNOWN_DEVICE)
when a device is unreachable, compared to 0x09 (HIDPP_ERROR_RESOURCE_ERROR)
that the older receivers return.

This patch silences this harmless error by treating
HIDPP_ERROR_UNKNOWN_DEVICE the same as HIDPP_ERROR_RESOURCE_ERROR
in hidpp_root_get_protocol_version().

There are other checks for HIDPP_ERROR_RESOURCE_ERROR found in
battery-related functions, however this receiver does not trigger them when
the device is disconnected.

Signed-off-by: Mavroudis Chatzilazaridis <mavchatz@protonmail.com>
---
 drivers/hid/hid-logitech-hidpp.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/hid/hid-logitech-hidpp.c b/drivers/hid/hid-logitech-hidpp.c
index aaef405a717e..1d46783384ed 100644
--- a/drivers/hid/hid-logitech-hidpp.c
+++ b/drivers/hid/hid-logitech-hidpp.c
@@ -969,7 +969,8 @@ static int hidpp_root_get_protocol_version(struct hidpp_device *hidpp)
 	}
 
 	/* the device might not be connected */
-	if (ret == HIDPP_ERROR_RESOURCE_ERROR)
+	if (ret == HIDPP_ERROR_RESOURCE_ERROR ||
+	    ret == HIDPP_ERROR_UNKNOWN_DEVICE)
 		return -EIO;
 
 	if (ret > 0) {
-- 
2.43.0

Re: [PATCH] HID: logitech-hidpp: Silence protocol errors on newer lightspeed receivers

[Stuart]

Tested on 6.17.0 with a handful of other patches:
 - https://lore.kernel.org/all/20250927234834.2635483-1-mavchatz@protonmail.com/
 - https://lore.kernel.org/all/20251002193025.2066319-1-mavchatz@protonmail.com/

Gets rid of that annoying warning on my Logitech G915 TKL keyboard
No regressions on my Logitech G502 Lightspeed Wireless mouse

Tested-by: Stuart Hayhurst <stuart.a.hayhurst@gmail.com>

Thanks,
Stuart

Re: [PATCH] HID: logitech-hidpp: Silence protocol errors on newer lightspeed receivers

[Jiri Kosina]

On Thu, 2 Oct 2025, Mavroudis Chatzilazaridis wrote:

> When logitech-hidpp tries to communicate with an unreachable device paired
> to a 046d:c547 lightspeed receiver, the following message is printed to the
> console:
> 
> hidpp_root_get_protocol_version: received protocol error 0x08
> 
> This occurs because this receiver returns 0x08 (HIDPP_ERROR_UNKNOWN_DEVICE)
> when a device is unreachable, compared to 0x09 (HIDPP_ERROR_RESOURCE_ERROR)
> that the older receivers return.
> 
> This patch silences this harmless error by treating
> HIDPP_ERROR_UNKNOWN_DEVICE the same as HIDPP_ERROR_RESOURCE_ERROR
> in hidpp_root_get_protocol_version().
> 
> There are other checks for HIDPP_ERROR_RESOURCE_ERROR found in
> battery-related functions, however this receiver does not trigger them when
> the device is disconnected.

Applied, thanks.

-- 
Jiri Kosina
SUSE Labs