Re: Linux "hid_led" vs "hidraw" USB HID question

[Heiner Kallweit <hkallweit1@gmail.com>]

On 10.11.2019 04:26, Tod E. Kurt wrote:
> HiI
> 
Hi Tod,

> Since you are listed as author of "hid-led.c": 
>   https://github.com/torvalds/linux/blob/master/drivers/hid/hid-led.c, 
> I was wondering if you could offer some insight on an issue I'm seeing.
> I'm a maintainer of "hidapi" and "node-hid", cross-platform C and NodeJs libraries for accessing HID devices, and I'm the creator of the ThingM blink(1) USB LED that "hid-led" controls.
> 
> On the distros I've seen (Ubuntu, Raspian) where "hid-led" is enabled, when inserting a blink(1) device, the "hid-led" driver appears to grab the device and remove it from available "hidraw" devices.  This makes generic hidraw-based systems (like "hidapi" and the upcoming Chrome WebHID) unable to see the blink(1)
> 
> I have tried blacklisting the "hid-led" module but the problem persist. Ffrom dmesg and lsmod the module does appear to not be loaded on reboot.
> 
> Any insights on what's going on?  Any tips on how to debug this or how to prevent this from occurring?
> 
When hid-led was written it was needed to add the LED devices to hid_have_special_driver list.
Else the driver can't take control over the device. Side effect is that even if hid-led
isn't loaded hid-generic can't take control.
I think since e04a0442d33b ("HID: core: remove the absolute need of hid_have_special_driver[]")
it's no longer needed to have the LED devices in hid_have_special_driver.
Could you please test the following patch? If hid-led is loaded is should control the
device, if it's blacklisted hid-generic should have the control.


diff --git a/drivers/hid/hid-quirks.c b/drivers/hid/hid-quirks.c
index c50bcd967..bdaab79f7 100644
--- a/drivers/hid/hid-quirks.c
+++ b/drivers/hid/hid-quirks.c
@@ -419,13 +419,6 @@ static const struct hid_device_id hid_have_special_driver[] = {
 #if IS_ENABLED(CONFIG_HID_LCPOWER)
 	{ HID_USB_DEVICE(USB_VENDOR_ID_LCPOWER, USB_DEVICE_ID_LCPOWER_LC1000) },
 #endif
-#if IS_ENABLED(CONFIG_HID_LED)
-	{ HID_USB_DEVICE(USB_VENDOR_ID_DREAM_CHEEKY, USB_DEVICE_ID_DREAM_CHEEKY_WN) },
-	{ HID_USB_DEVICE(USB_VENDOR_ID_DREAM_CHEEKY, USB_DEVICE_ID_DREAM_CHEEKY_FA) },
-	{ HID_USB_DEVICE(USB_VENDOR_ID_MICROCHIP, USB_DEVICE_ID_LUXAFOR) },
-	{ HID_USB_DEVICE(USB_VENDOR_ID_RISO_KAGAKU, USB_DEVICE_ID_RI_KA_WEBMAIL) },
-	{ HID_USB_DEVICE(USB_VENDOR_ID_THINGM, USB_DEVICE_ID_BLINK1) },
-#endif
 #if IS_ENABLED(CONFIG_HID_LENOVO)
 	{ HID_USB_DEVICE(USB_VENDOR_ID_LENOVO, USB_DEVICE_ID_LENOVO_TPKBD) },
 	{ HID_USB_DEVICE(USB_VENDOR_ID_LENOVO, USB_DEVICE_ID_LENOVO_CUSBKBD) },
-- 
2.24.0

> I can send you blink(1) devices and "hidapi" test programs if you'd like to try to replicate this.
> 
Thanks for the offer, I've got a blink(1) already. Just tested the patch with this device
and it worked properly like described above.

> Thanks!
> -=Tod

Heiner