Re: [PATCH v3 04/11] HID: haptic: introduce hid_haptic_device

[Randy Dunlap <rdunlap@infradead.org>]

Hi,

I think I found it... see below.


On 10/9/25 11:48 PM, Thorsten Leemhuis wrote:
> [Top-Posting for easier consumption]
> 
> Mainly writing this mail to bring Lucas GISSOT in here, who reported the
> same error yesterday here:
> https://lore.kernel.org/all/aOgvA8Jiofcnk2xb@ARSENIURE.localdomain/
> 
> Lucas there suggested:
> """but it seems to me that the #if IS_ENABLED(CONFIG_HID_HAPTIC) in
> hid-haptic.h should be replaced by IS_BUILTIN(CONFIG_HID_HAPTIC) and
> Kconfig updated."""
> 
> And Randy: Thx for the closer investigation! It explains some of the
> "that feels odd, am I holding this wrong" feeling I had when reporting this.
> 
> Ciao, Thorsten
> 
> On 10/10/25 06:50, Randy Dunlap wrote:
>> On 10/9/25 7:43 AM, Thorsten Leemhuis wrote:
>>> On 8/19/25 01:08, Jonathan Denose wrote:
>>>> From: Angela Czubak <aczubak@google.com>
>>>>
>>>> Define a new structure that contains simple haptic device configuration
>>>> as well as current state.
>>>> Add functions that recognize auto trigger and manual trigger reports
>>>> as well as save their addresses.Hi,
>>>> Verify that the pressure unit is either grams or newtons.
>>>> Mark the input device as a haptic touchpad if the unit is correct and
>>>> the reports are found.
>>>>  [...]
>>>> +config HID_HAPTIC
>>>> +	tristate "Haptic touchpad support"
>>>> +	default n
>>>> +	help
>>>> +	Support for touchpads with force sensors and haptic actuators instead of a
>>>> +	traditional button.
>>>> +	Adds extra parsing and FF device for the hid multitouch driver.
>>>> +	It can be used for Elan 2703 haptic touchpad.
>>>> +
>>>> +	If unsure, say N.
>>>> +
>>>>  menu "Special HID drivers"
>>>
>>> I suspect this change is related to a build error I ran into today:
>>>
>>>   MODPOST Module.symvers
>>> ERROR: modpost: "hid_haptic_init" [drivers/hid/hid-multitouch.ko] undefined!
>>> ERROR: modpost: "hid_haptic_pressure_increase" [drivers/hid/hid-multitouch.ko] undefined!
>>> ERROR: modpost: "hid_haptic_check_pressure_unit" [drivers/hid/hid-multitouch.ko] undefined!
>>> ERROR: modpost: "hid_haptic_input_configured" [drivers/hid/hid-multitouch.ko] undefined!
>>> ERROR: modpost: "hid_haptic_input_mapping" [drivers/hid/hid-multitouch.ko] undefined!
>>> ERROR: modpost: "hid_haptic_feature_mapping" [drivers/hid/hid-multitouch.ko] undefined!
>>> ERROR: modpost: "hid_haptic_pressure_reset" [drivers/hid/hid-multitouch.ko] undefined!
>>> make[3]: *** [/home/thl/var/linux.dev/scripts/Makefile.modpost:147: Module.symvers] Error 1
>>>
>>> The config where this occurred had this:
>>>
>>> CONFIG_HID=y
>>> CONFIG_HID_MULTITOUCH=m
>>> CONFIG_HID_HAPTIC=m
>>>
>>> Changing the latter to "CONFIG_HID_HAPTIC=y" fixed the problem for me.
>>
>> Sure, but that's just covering up the problem.
>>> First, I get this build error:
>>
>> ERROR: modpost: missing MODULE_LICENSE() in drivers/hid/hid-haptic.o
>> WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/hid/hid-haptic.o
>>

ISTM that tristate is incompatible with this newly added Makefile
line:

+hid-$(CONFIG_HID_HAPTIC)       += hid-haptic.o

hid-* lists files that should be builtin, not loadable modules.
These should all be hid-y.  AFAIK, hid-m is not useful.
(A maintainer can correct me as needed.)

So adding a MODULE_LICENSE() and MODULE_DESCRIPTION() to
hid-haptic.c and changing drivers/hid/Makefile to use
obj-$(CONFIG_HID_HAPTIC_	+= hid-haptic.o

fixes the build errors for me.

Angela, Jonathan D., is there any reason that
hid-haptic needs to be builtin instead of a loadable
module?  It's no problem for hid-multitouch.ko to call
into hid-haptic.ko (both as loadable modules) as long as
hid-haptic.ko is loaded first.

Thanks.

~Randy
---
---
 drivers/hid/hid-haptic.c |    3 +++
 1 file changed, 3 insertions(+)

--- linux.orig/drivers/hid/hid-haptic.c
+++ linux/drivers/hid/hid-haptic.c
@@ -10,6 +10,9 @@
 
 #include "hid-haptic.h"
 
+MODULE_DESCRIPTION("HID haptic touchpad support");
+MODULE_LICENSE("GPL");
+
 void hid_haptic_feature_mapping(struct hid_device *hdev,
 				struct hid_haptic_device *haptic,
 				struct hid_field *field, struct hid_usage *usage)
---
 drivers/hid/Makefile |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- linux.orig/drivers/hid/Makefile
+++ linux/drivers/hid/Makefile
@@ -4,7 +4,8 @@
 #
 hid-y			:= hid-core.o hid-input.o hid-quirks.o
 hid-$(CONFIG_DEBUG_FS)		+= hid-debug.o
-hid-$(CONFIG_HID_HAPTIC)	+= hid-haptic.o
+
+obj-$(CONFIG_HID_HAPTIC)	+= hid-haptic.o
 
 obj-$(CONFIG_HID_BPF)		+= bpf/