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

[Jonathan Denose]

Hi all,

Thanks for looking into this.

On Fri, Oct 10, 2025 at 1:55 PM Randy Dunlap <rdunlap@xxxxxxxxxxxxx> wrote:
>
> 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@xxxxxxxxxx>
> >>>>
> >>>> 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.
>
As long as hid-multitouch.ko is able to call into hid-haptic.ko I
don't see any issues, but is there a way to enforce that when
CONFIG_HID_HAPTIC is enabled, hid-haptic.ko will be loaded before
hid-multitouch.ko?
>
> 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/
>
>
--
Jonathan