Download raw body.
imt(4)/umt(4): finding HID report IDs
Hello!
If you guys are still hung up on the name of this macro:
#define IS_TOP_LEVEL_USAGE(u) ((((u) >> 16) & 0xffff) == HUP_BUTTON || \
(u) == HID_USAGE2(HUP_DIGITIZERS, HUD_CONTACTCOUNT))
let me offer my 2 cents...
What you are actually trying to match with it is a usage ID for a
button or something equivalent.
So "TOP_LEVEL_USAGE" is perfect for the first half of the Macro,
but the second half, after the ||, it is not. Sorry, Ulf!
My propopsal:
#define IS_USAGEID_FOR_BUTTON(u) ...
Thomas
> Ulf Brosziewski <ulf.brosziewski@t-online.de> hat am 16.07.2025 12:49 CEST geschrieben:
>
>
> On 7/16/25 00:07, Mark Kettenis wrote:
> >> Date: Tue, 15 Jul 2025 23:08:29 +0200
> >> From: Ulf Brosziewski <ulf.brosziewski@t-online.de>
> >>
> >> Anybody?
> >
> > The same comment about "top-level usage" not being a thing in the spec
> > and being inconsistent with the existing comments applies here as well.
> >
> > Otherwise this makes (some) sense to me.
>
> In hid_find_report(), "top-level usage" is the more accurate term because
> it refers to collections without a parent collection in the descriptor.
> However, this should be an application collection ("Each top level
> collection must be an application collection", hid1_11, p. 67). I could
> rename "top_usage" to "app_usage" and add the check for the collection
> type (h.collection == HCOLL_APPLICATION).
>
> Is something else missing? More tests would be nice, of course, but it's
> summertime. I had checked a userland version of hid_find_report() with a
> set of report descriptors grabbed from the web.
>
> Skipping unknown collections is a recommendation from the specification:
> "If the Usage attached to a collection is unknown to an application,
> then the application should ignore the collection and all Usages
> contained in the collection. A collection can be used to modify the
> meaning of the Usages that it contains [...]" (hud1_6, p. 20)
>
>
> >
> >> On 7/2/25 01:37, Ulf Brosziewski wrote:
> >>> The way imt(4) and umt(4) search for report IDs is broken. Depending
> >>> on the structure and distribution of IDs in a report descriptor, it might
> >>> succeed, or fail with wrong ID values (as has been reported by Thomas
> >>> Dettbarn, see https://marc.info/?l=openbsd-tech&m=174841257723328&w=2 ).
> >>>
> >>> The hid_*_collection functions only provide partial information, which,
> >>> in isolation, may be useless if you aren't lucky and deal with simple,
> >>> uniform descriptors.
> >>>
> >>> The patch adds another helper function to hid.c, which permits searching
> >>> for several report items at once, and filters out "unknown" collections
> >>> (see the comment in the diff). It doesn't put further constraints on the
> >>> search and the structure of the descriptor, but the heuristic might be
> >>> safe enough for most practical purposes. However, my experience with the
> >>> real HID world is limited, comments and hints would be appreciated.
> >>>
> >>> The patch moves the search for "PTP" reports to hidmt, and adapts imt
> >>> and umt accordingly. Please note that it also contains a fix for another
> >>> bug in hidmt (see https://marc.info/?l=openbsd-tech&m=175101436027656&w=2 ).
> >>> It may be hidden by the faulty report search; that's why for tests, it
> >>> makes sense to combine the patches.
> >>>
> >>> Tests, comments, and OKs would be welcome.
> >>>
> >>>
> >>> Index: dev/hid/hid.c
> >>> ===================================================================
> >>> RCS file: /cvs/src/sys/dev/hid/hid.c,v
> >>> retrieving revision 1.7
> >>> diff -u -p -r1.7 hid.c
> >>> --- dev/hid/hid.c 10 May 2024 10:49:10 -0000 1.7
> >>> +++ dev/hid/hid.c 1 Jul 2025 20:11:57 -0000
> >>> @@ -706,3 +706,70 @@ hid_get_id_of_collection(const void *des
> >>> hid_end_parse(hd);
> >>> return -1;
> >>> }
> >>> +
> >>> +/*
> >>> + * Find the first report that contains each of the given "usages"
> >>> + * and belongs to a top-level collection with the 'top_usage' type.
> >>> + * The size of the 'usages' array must be in the range [1..32].
> >>> + *
> >>> + * If 'coll_usages' is NULL, the search will skip collections with
> >>> + * usages from vendor pages (0xFF00 - 0xFFFF).
> >>> + *
> >>> + * If 'coll_usages' is non-NULL, it must point to a 0-terminated
> >>> + * sequence of collection usages, and the search will skip collections
> >>> + * with usages not present in this set. (It isn't necessary to include
> >>> + * the top-level usage here).
> >>> + *
> >>> + * Return Values:
> >>> + * -1: No match
> >>> + * 0: Success (single report without an ID)
> >>> + * [1..255]: Report ID
> >>> + */
> >>> +int
> >>> +hid_find_report(const void *desc, int len, enum hid_kind kind,
> >>> + int32_t top_usage, int n_usages, int32_t *usages, int32_t *coll_usages)
> >>> +{
> >>> + struct hid_data *hd;
> >>> + struct hid_item h;
> >>> + uint32_t matches;
> >>> + int i, cur_id, skip;
> >>> +
> >>> + hd = hid_start_parse(desc, len, hid_all);
> >>> + for (cur_id = -1, skip = 0; hid_get_item(hd, &h); ) {
> >>> + if (cur_id != h.report_ID) {
> >>> + matches = 0;
> >>> + cur_id = h.report_ID;
> >>> + }
> >>> + if (h.kind == hid_collection) {
> >>> + if (skip)
> >>> + continue;
> >>> + if (h.collevel == 1) {
> >>> + if (h.usage != top_usage)
> >>> + skip = 1;
> >>> + } else if (coll_usages != NULL) {
> >>> + for (i = 0; coll_usages[i] != h.usage; i++)
> >>> + if (coll_usages[i] == 0) {
> >>> + skip = h.collevel;
> >>> + break;
> >>> + }
> >>> + } else if (((h.usage >> 16) & 0xffff) >= 0xff00) {
> >>> + skip = h.collevel;
> >>> + }
> >>> + } else if (h.kind == hid_endcollection) {
> >>> + if (h.collevel < skip)
> >>> + skip = 0;
> >>> + }
> >>> + if (h.kind != kind || skip)
> >>> + continue;
> >>> + for (i = 0; i < n_usages; i++)
> >>> + if (h.usage == usages[i] && !(matches & (1 << i))) {
> >>> + matches |= (1 << i);
> >>> + if (matches != (1 << n_usages) - 1)
> >>> + break;
> >>> + hid_end_parse(hd);
> >>> + return (h.report_ID);
> >>> + }
> >>> + }
> >>> + hid_end_parse(hd);
> >>> + return (-1);
> >>> +}
> >>> Index: dev/hid/hid.h
> >>> ===================================================================
> >>> RCS file: /cvs/src/sys/dev/hid/hid.h,v
> >>> retrieving revision 1.11
> >>> diff -u -p -r1.11 hid.h
> >>> --- dev/hid/hid.h 12 Aug 2023 20:47:06 -0000 1.11
> >>> +++ dev/hid/hid.h 1 Jul 2025 20:11:57 -0000
> >>> @@ -95,6 +95,8 @@ uint32_t hid_get_udata(const uint8_t *bu
> >>> int hid_is_collection(const void *, int, uint8_t, int32_t);
> >>> struct hid_data *hid_get_collection_data(const void *, int, int32_t, uint32_t);
> >>> int hid_get_id_of_collection(const void *, int, int32_t, uint32_t);
> >>> +int hid_find_report(const void *, int len, enum hid_kind, int32_t,
> >>> + int, int32_t *, int32_t *);
> >>>
> >>> #endif /* _KERNEL */
> >>>
> >>> Index: dev/hid/hidmt.c
> >>> ===================================================================
> >>> RCS file: /cvs/src/sys/dev/hid/hidmt.c,v
> >>> retrieving revision 1.13
> >>> diff -u -p -r1.13 hidmt.c
> >>> --- dev/hid/hidmt.c 16 Oct 2022 20:17:08 -0000 1.13
> >>> +++ dev/hid/hidmt.c 1 Jul 2025 20:11:57 -0000
> >>> @@ -42,6 +42,9 @@
> >>> #define DPRINTF(x)
> >>> #endif
> >>>
> >>> +#define IS_TOP_LEVEL_USAGE(u) ((((u) >> 16) & 0xffff) == HUP_BUTTON || \
> >>> + (u) == HID_USAGE2(HUP_DIGITIZERS, HUD_CONTACTCOUNT))
> >>> +
> >>> #define HID_UNIT_CM 0x11
> >>> #define HID_UNIT_INCH 0x13
> >>>
> >>> @@ -373,7 +376,7 @@ hidmt_input(struct hidmt *mt, uint8_t *d
> >>>
> >>> bzero(&hc, sizeof(struct hidmt_contact));
> >>> }
> >>> - else if (!firstu)
> >>> + else if (!firstu && !IS_TOP_LEVEL_USAGE(hi->usage))
> >>> firstu = hi->usage;
> >>>
> >>> switch (hi->usage) {
> >>> @@ -530,4 +533,41 @@ void
> >>> hidmt_disable(struct hidmt *mt)
> >>> {
> >>> mt->sc_enabled = 0;
> >>> +}
> >>> +
> >>> +int
> >>> +hidmt_find_winptp_reports(const void *desc, int len, int *input_rid,
> >>> + int *config_rid, int *cap_rid)
> >>> +{
> >>> + static int32_t ptp_collections[] = {
> >>> + HID_USAGE2(HUP_DIGITIZERS, HUD_FINGER), 0
> >>> + };
> >>> + static int32_t input_usages[] = {
> >>> + /* top-level */
> >>> + HID_USAGE2(HUP_DIGITIZERS, HUD_CONTACTCOUNT),
> >>> + /* contact-level */
> >>> + HID_USAGE2(HUP_GENERIC_DESKTOP, HUG_X),
> >>> + HID_USAGE2(HUP_GENERIC_DESKTOP, HUG_Y),
> >>> + HID_USAGE2(HUP_DIGITIZERS, HUD_CONFIDENCE),
> >>> + HID_USAGE2(HUP_DIGITIZERS, HUD_TIP_SWITCH),
> >>> + HID_USAGE2(HUP_DIGITIZERS, HUD_CONTACTID),
> >>> + };
> >>> + static int32_t cfg_usages[] = {
> >>> + HID_USAGE2(HUP_DIGITIZERS, HUD_INPUT_MODE),
> >>> + };
> >>> + static int32_t cap_usages[] = {
> >>> + HID_USAGE2(HUP_DIGITIZERS, HUD_CONTACT_MAX),
> >>> + };
> >>> +
> >>> + *input_rid = hid_find_report(desc, len, hid_input,
> >>> + HID_USAGE2(HUP_DIGITIZERS, HUD_TOUCHPAD),
> >>> + nitems(input_usages), input_usages, ptp_collections);
> >>> + *config_rid = hid_find_report(desc, len, hid_feature,
> >>> + HID_USAGE2(HUP_DIGITIZERS, HUD_CONFIG),
> >>> + nitems(cfg_usages), cfg_usages, ptp_collections);
> >>> + *cap_rid = hid_find_report(desc, len, hid_feature,
> >>> + HID_USAGE2(HUP_DIGITIZERS, HUD_TOUCHPAD),
> >>> + nitems(cap_usages), cap_usages, ptp_collections);
> >>> +
> >>> + return (*input_rid > 0 && *config_rid > 0 && *cap_rid > 0);
> >>> }
> >>> Index: dev/hid/hidmtvar.h
> >>> ===================================================================
> >>> RCS file: /cvs/src/sys/dev/hid/hidmtvar.h,v
> >>> retrieving revision 1.8
> >>> diff -u -p -r1.8 hidmtvar.h
> >>> --- dev/hid/hidmtvar.h 8 Nov 2019 01:20:22 -0000 1.8
> >>> +++ dev/hid/hidmtvar.h 1 Jul 2025 20:11:57 -0000
> >>> @@ -77,3 +77,4 @@ int hidmt_enable(struct hidmt *);
> >>> void hidmt_input(struct hidmt *, uint8_t *, u_int);
> >>> int hidmt_ioctl(struct hidmt *, u_long, caddr_t, int, struct proc *);
> >>> int hidmt_setup(struct device *, struct hidmt *, void *, int);
> >>> +int hidmt_find_winptp_reports(const void *, int, int *, int *, int *);
> >>> Index: dev/i2c/imt.c
> >>> ===================================================================
> >>> RCS file: /cvs/src/sys/dev/i2c/imt.c,v
> >>> retrieving revision 1.6
> >>> diff -u -p -r1.6 imt.c
> >>> --- dev/i2c/imt.c 13 May 2024 01:15:50 -0000 1.6
> >>> +++ dev/i2c/imt.c 1 Jul 2025 20:11:57 -0000
> >>> @@ -56,8 +56,6 @@ const struct wsmouse_accessops imt_acces
> >>> };
> >>>
> >>> int imt_match(struct device *, void *, void *);
> >>> -int imt_find_winptp_reports(struct ihidev_softc *, void *, int,
> >>> - struct imt_softc *);
> >>> void imt_attach(struct device *, struct device *, void *);
> >>> int imt_hidev_get_report(struct device *, int, int, void *, int);
> >>> int imt_hidev_set_report(struct device *, int, int, void *, int);
> >>> @@ -78,16 +76,17 @@ int
> >>> imt_match(struct device *parent, void *match, void *aux)
> >>> {
> >>> struct ihidev_attach_arg *iha = (struct ihidev_attach_arg *)aux;
> >>> - struct imt_softc sc;
> >>> + int input_rid, conf_rid, cap_rid;
> >>> int size;
> >>> void *desc;
> >>>
> >>> if (iha->reportid == IHIDEV_CLAIM_MULTIPLEID) {
> >>> ihidev_get_report_desc(iha->parent, &desc, &size);
> >>> - if (imt_find_winptp_reports(iha->parent, desc, size, &sc)) {
> >>> - iha->claims[0] = sc.sc_rep_input;
> >>> - iha->claims[1] = sc.sc_rep_config;
> >>> - iha->claims[2] = sc.sc_rep_cap;
> >>> + if (hidmt_find_winptp_reports(desc, size,
> >>> + &input_rid, &conf_rid, &cap_rid)) {
> >>> + iha->claims[0] = input_rid;
> >>> + iha->claims[1] = conf_rid;
> >>> + iha->claims[2] = cap_rid;
> >>> iha->nclaims = 3;
> >>> return (IMATCH_DEVCLASS_DEVSUBCLASS);
> >>> }
> >>> @@ -96,49 +95,6 @@ imt_match(struct device *parent, void *m
> >>> return (IMATCH_NONE);
> >>> }
> >>>
> >>> -int
> >>> -imt_find_winptp_reports(struct ihidev_softc *parent, void *desc, int size,
> >>> - struct imt_softc *sc)
> >>> -{
> >>> - int repid;
> >>> - int input = 0, conf = 0, cap = 0;
> >>> -
> >>> - if (sc != NULL) {
> >>> - sc->sc_rep_input = -1;
> >>> - sc->sc_rep_config = -1;
> >>> - sc->sc_rep_cap = -1;
> >>> - }
> >>> -
> >>> - for (repid = 0; repid < parent->sc_nrepid; repid++) {
> >>> - if (hid_report_size(desc, size, hid_input, repid) == 0 &&
> >>> - hid_report_size(desc, size, hid_output, repid) == 0 &&
> >>> - hid_report_size(desc, size, hid_feature, repid) == 0)
> >>> - continue;
> >>> -
> >>> - if (hid_is_collection(desc, size, repid,
> >>> - HID_USAGE2(HUP_DIGITIZERS, HUD_TOUCHPAD))) {
> >>> - input = 1;
> >>> - if (sc != NULL && sc->sc_rep_input == -1)
> >>> - sc->sc_rep_input = repid;
> >>> - } else if (hid_is_collection(desc, size, repid,
> >>> - HID_USAGE2(HUP_DIGITIZERS, HUD_CONFIG))) {
> >>> - conf = 1;
> >>> - if (sc != NULL && sc->sc_rep_config == -1)
> >>> - sc->sc_rep_config = repid;
> >>> - }
> >>> -
> >>> - /* capabilities report could be anywhere */
> >>> - if (hid_locate(desc, size, HID_USAGE2(HUP_DIGITIZERS,
> >>> - HUD_CONTACT_MAX), repid, hid_feature, NULL, NULL)) {
> >>> - cap = 1;
> >>> - if (sc != NULL && sc->sc_rep_cap == -1)
> >>> - sc->sc_rep_cap = repid;
> >>> - }
> >>> - }
> >>> -
> >>> - return (conf && input && cap);
> >>> -}
> >>> -
> >>> void
> >>> imt_attach(struct device *parent, struct device *self, void *aux)
> >>> {
> >>> @@ -152,7 +108,8 @@ imt_attach(struct device *parent, struct
> >>> sc->sc_hdev.sc_parent = iha->parent;
> >>>
> >>> ihidev_get_report_desc(iha->parent, &desc, &size);
> >>> - imt_find_winptp_reports(iha->parent, desc, size, sc);
> >>> + hidmt_find_winptp_reports(desc, size, &sc->sc_rep_input,
> >>> + &sc->sc_rep_config, &sc->sc_rep_cap);
> >>>
> >>> memset(mt, 0, sizeof(sc->sc_mt));
> >>>
> >>> Index: dev/usb/umt.c
> >>> ===================================================================
> >>> RCS file: /cvs/src/sys/dev/usb/umt.c,v
> >>> retrieving revision 1.8
> >>> diff -u -p -r1.8 umt.c
> >>> --- dev/usb/umt.c 26 May 2024 20:06:27 -0000 1.8
> >>> +++ dev/usb/umt.c 1 Jul 2025 20:11:57 -0000
> >>> @@ -60,8 +60,6 @@ const struct wsmouse_accessops umt_acces
> >>> };
> >>>
> >>> int umt_match(struct device *, void *, void *);
> >>> -int umt_find_winptp_reports(struct uhidev_softc *, void *, int, int *,
> >>> - int *, int *);
> >>> void umt_attach(struct device *, struct device *, void *);
> >>> int umt_hidev_get_report(struct device *, int, int, void *, int);
> >>> int umt_hidev_set_report(struct device *, int, int, void *, int);
> >>> @@ -88,7 +86,7 @@ umt_match(struct device *parent, void *m
> >>>
> >>> if (UHIDEV_CLAIM_MULTIPLE_REPORTID(uha)) {
> >>> uhidev_get_report_desc(uha->parent, &desc, &size);
> >>> - if (umt_find_winptp_reports(uha->parent, desc, size, &input,
> >>> + if (hidmt_find_winptp_reports(desc, size, &input,
> >>> &conf, &cap)) {
> >>> uha->claimed[input] = 1;
> >>> uha->claimed[conf] = 1;
> >>> @@ -100,50 +98,6 @@ umt_match(struct device *parent, void *m
> >>> return (UMATCH_NONE);
> >>> }
> >>>
> >>> -int
> >>> -umt_find_winptp_reports(struct uhidev_softc *parent, void *desc, int size,
> >>> - int *input, int *config, int *cap)
> >>> -{
> >>> - int repid;
> >>> - int finput = 0, fconf = 0, fcap = 0;
> >>> -
> >>> - if (input != NULL)
> >>> - *input = -1;
> >>> - if (config != NULL)
> >>> - *config = -1;
> >>> - if (cap != NULL)
> >>> - *cap = -1;
> >>> -
> >>> - for (repid = 0; repid < parent->sc_nrepid; repid++) {
> >>> - if (hid_report_size(desc, size, hid_input, repid) == 0 &&
> >>> - hid_report_size(desc, size, hid_output, repid) == 0 &&
> >>> - hid_report_size(desc, size, hid_feature, repid) == 0)
> >>> - continue;
> >>> -
> >>> - if (hid_is_collection(desc, size, repid,
> >>> - HID_USAGE2(HUP_DIGITIZERS, HUD_TOUCHPAD))) {
> >>> - finput = 1;
> >>> - if (input != NULL && *input == -1)
> >>> - *input = repid;
> >>> - } else if (hid_is_collection(desc, size, repid,
> >>> - HID_USAGE2(HUP_DIGITIZERS, HUD_CONFIG))) {
> >>> - fconf = 1;
> >>> - if (config != NULL && *config == -1)
> >>> - *config = repid;
> >>> - }
> >>> -
> >>> - /* capabilities report could be anywhere */
> >>> - if (hid_locate(desc, size, HID_USAGE2(HUP_DIGITIZERS,
> >>> - HUD_CONTACT_MAX), repid, hid_feature, NULL, NULL)) {
> >>> - fcap = 1;
> >>> - if (cap != NULL && *cap == -1)
> >>> - *cap = repid;
> >>> - }
> >>> - }
> >>> -
> >>> - return (fconf && finput && fcap);
> >>> -}
> >>> -
> >>> void
> >>> umt_attach(struct device *parent, struct device *self, void *aux)
> >>> {
> >>> @@ -163,7 +117,7 @@ umt_attach(struct device *parent, struct
> >>> sc->sc_quirks = usbd_get_quirks(sc->sc_hdev.sc_udev)->uq_flags;
> >>>
> >>> uhidev_get_report_desc(uha->parent, &desc, &size);
> >>> - umt_find_winptp_reports(uha->parent, desc, size, &sc->sc_rep_input,
> >>> + hidmt_find_winptp_reports(desc, size, &sc->sc_rep_input,
> >>> &sc->sc_rep_config, &sc->sc_rep_cap);
> >>>
> >>> memset(mt, 0, sizeof(sc->sc_mt));
> >>>
> >>
> >>
imt(4)/umt(4): finding HID report IDs