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    SubjectRe: [RFC] HID: input: do not increment usages when a duplicate is found
    A bit late, but this has bitten us again recently. below are two
    typos/nitpicks comments

    On Mon, Jun 19, 2017 at 11:55:13AM +0200, Benjamin Tissoires wrote:
    > This is something that bothered us from a long time. When hid-input

    'for a long time'

    > doesn't know how to map a usage, it uses *_MISC. But there is something
    > else which increments the usage if the evdev code is already used.

    this sentence is a bit confusing, needs to be reworded.

    Acked-by: Peter Hutterer <peter.hutterer@who-t.net>

    Cheers,
    Peter

    > This leads to few issues:
    > - some devices may have their ABS_X mapped to ABS_Y if they export a bad
    > set of usages (see the DragonRise joysticks IIRC -> fixed in a specific
    > HID driver)
    > - *_MISC + N might (will) conflict with other defined axes (my Logitech
    > H800 exports some multitouch axes because of that)
    > - this prevents to freely add some new evdev usages, because "hey, my
    > headset will now report ABS_COFFEE, and it's not coffee capable".
    >
    > So let's try to kill this nonsense, and hope we won't break too many
    > devices.
    >
    > I my headset case, the ABS_MISC axes are created because of some
    > proprietary usages, so we might not break that many devices.
    >
    > For backward compatibility, a quirk HID_QUIRK_INCREMENT_USAGE_ON_DUPLICATE
    > is created and can be applied to any device that needs this behavior.
    >
    > Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
    > ---
    >
    > Hi,
    >
    > well, given I'd like to have a formal "go" before spending too much time
    > in this, I am sending this a an RFC.
    > This won't solve all the user space problems (especially the detection of
    > non-mt devices based on ABS_MT_SLOT - 1 being set), but it should help us
    > extending the other event types.
    >
    > Jiri, this patch applies on top of for-next + my series that creates
    > HID_QUIRK_HAVE_SPECIAL_DRIVER, so do not expect it to apply cleanly on your
    > tree :)
    >
    > Cheers,
    > Benjamin
    >
    > drivers/hid/hid-input.c | 33 +++++++++++++++++++++++++++++++--
    > include/linux/hid.h | 2 ++
    > 2 files changed, 33 insertions(+), 2 deletions(-)
    >
    > diff --git a/drivers/hid/hid-input.c b/drivers/hid/hid-input.c
    > index ccdff1e..9a9be89 100644
    > --- a/drivers/hid/hid-input.c
    > +++ b/drivers/hid/hid-input.c
    > @@ -1025,8 +1025,31 @@ static void hidinput_configure_usage(struct hid_input *hidinput, struct hid_fiel
    >
    > set_bit(usage->type, input->evbit);
    >
    > - while (usage->code <= max && test_and_set_bit(usage->code, bit))
    > - usage->code = find_next_zero_bit(bit, max + 1, usage->code);
    > + /*
    > + * This part is *really* controversial:
    > + * - HID aims at being generic so we should do our best to export
    > + * all incoming events
    > + * - HID describes what events are, so there is no reason for ABS_X
    > + * to be mapped to ABS_Y
    > + * - HID is using *_MISC+N as a default value, but nothing prevents
    > + * *_MISC+N to overwrite a legitimate even, which confuses userspace
    > + * (for instance ABS_MISC + 7 is ABS_MT_SLOT, which has a different
    > + * processing)
    > + *
    > + * If devices still want to use this (at their own risk), they will
    > + * have to use the quirk HID_QUIRK_INCREMENT_USAGE_ON_DUPLICATE, but
    > + * the default should be a reliable mapping.
    > + */
    > + while (usage->code <= max && test_and_set_bit(usage->code, bit)) {
    > + if (device->quirks & HID_QUIRK_INCREMENT_USAGE_ON_DUPLICATE) {
    > + usage->code = find_next_zero_bit(bit,
    > + max + 1,
    > + usage->code);
    > + } else {
    > + device->status |= HID_STAT_DUP_DETECTED;
    > + goto ignore;
    > + }
    > + }
    >
    > if (usage->code > max)
    > goto ignore;
    > @@ -1527,6 +1550,8 @@ int hidinput_connect(struct hid_device *hid, unsigned int force)
    > INIT_LIST_HEAD(&hid->inputs);
    > INIT_WORK(&hid->led_work, hidinput_led_worker);
    >
    > + hid->status &= ~HID_STAT_DUP_DETECTED;
    > +
    > if (!force) {
    > for (i = 0; i < hid->maxcollection; i++) {
    > struct hid_collection *col = &hid->collection[i];
    > @@ -1593,6 +1618,10 @@ int hidinput_connect(struct hid_device *hid, unsigned int force)
    > goto out_unwind;
    > }
    >
    > + if (hid->status & HID_STAT_DUP_DETECTED)
    > + hid_info(hid,
    > + "Some usages could not be mapped, please use HID_QUIRK_INCREMENT_USAGE_ON_DUPLICATE if this is legitimate.\n");
    > +
    > return 0;
    >
    > out_unwind:
    > diff --git a/include/linux/hid.h b/include/linux/hid.h
    > index 7a473bf..245d1ac 100644
    > --- a/include/linux/hid.h
    > +++ b/include/linux/hid.h
    > @@ -340,6 +340,7 @@ struct hid_item {
    > #define HID_QUIRK_SKIP_OUTPUT_REPORT_ID 0x00020000
    > #define HID_QUIRK_NO_OUTPUT_REPORTS_ON_INTR_EP 0x00040000
    > #define HID_QUIRK_HAVE_SPECIAL_DRIVER 0x00080000
    > +#define HID_QUIRK_INCREMENT_USAGE_ON_DUPLICATE 0x00100000
    > #define HID_QUIRK_FULLSPEED_INTERVAL 0x10000000
    > #define HID_QUIRK_NO_INIT_REPORTS 0x20000000
    > #define HID_QUIRK_NO_IGNORE 0x40000000
    > @@ -491,6 +492,7 @@ struct hid_output_fifo {
    >
    > #define HID_STAT_ADDED 1
    > #define HID_STAT_PARSED 2
    > +#define HID_STAT_DUP_DETECTED 3
    >
    > struct hid_input {
    > struct list_head list;
    > --
    > 2.9.4
    >

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