Re: [PATCH 1/5] HID: hid-multitouch: fix wrong protocol detection

From: Benjamin Tissoires
Date: Wed May 09 2012 - 15:04:31 EST


Hi Henrik,

thanks for the review.
Some comments inlined:

On Sun, May 6, 2012 at 9:01 PM, Henrik Rydberg <rydberg@xxxxxxxxxxx> wrote:
> Hi Benjamin,
>
>> The previous implementation introduced a randomness in the splitting
>> of the different touches reported by the device. This version is more
>> robust as we don't rely on hi->input->absbit, but on our own structure.
>>
>> This also prepares hid-multitouch to better support Win8 devices.
>>
>> Signed-off-by: Benjamin Tissoires <benjamin.tissoires@xxxxxxx>
>> ---
>>  drivers/hid/hid-multitouch.c |   58 +++++++++++++++++++++++++++++++++--------
>>  1 files changed, 46 insertions(+), 12 deletions(-)
>>
>> diff --git a/drivers/hid/hid-multitouch.c b/drivers/hid/hid-multitouch.c
>> index 84bb32e..c6ffb05 100644
>> --- a/drivers/hid/hid-multitouch.c
>> +++ b/drivers/hid/hid-multitouch.c
>> @@ -70,9 +70,16 @@ struct mt_class {
>>       bool is_indirect;       /* true for touchpads */
>>  };
>>
>> +struct mt_fields {
>> +     unsigned usages[HID_MAX_FIELDS];
>> +     unsigned int length;
>> +};
>> +
>>  struct mt_device {
>>       struct mt_slot curdata; /* placeholder of incoming data */
>>       struct mt_class mtclass;        /* our mt device class */
>> +     struct mt_fields *fields;       /* temporary placeholder for storing the
>> +                                        multitouch fields */
>
> Why not skip the pointer here?

well, the idea was to keep the memory footprint low. As these values
are only needed at init, then I freed them once I finished using them.
I can of course skip the pointer, but in that case, wouldn't the
struct declaration be worthless?

>
>>       unsigned last_field_index;      /* last field index of the report */
>>       unsigned last_slot_field;       /* the last field of a slot */
>>       __s8 inputmode;         /* InputMode HID feature, -1 if non-existent */
>> @@ -275,11 +282,15 @@ static void set_abs(struct input_dev *input, unsigned int code,
>>       input_set_abs_params(input, code, fmin, fmax, fuzz, 0);
>>  }
>>
>> -static void set_last_slot_field(struct hid_usage *usage, struct mt_device *td,
>> +static void mt_store_field(struct hid_usage *usage, struct mt_device *td,
>>               struct hid_input *hi)
>
> How about adding the last_field_index here also, using a function like

I'm not a big fan of this idea.
last_field_index represent the last mt field, was it local or global
(i.e. per touch or global to the report).
mt_store_field stores only the local (per-touch) information to be
able to divide the array by the number of touch. Adding the global
items there too will force us to introduce a switch to exclude global
items.

Cheers,
Benjamin

>
> static void mt_store_field(struct mt_device *td, struct hid_input *hi,
>                        struct hid_field *field, struct hid_usage *usage)
>
>>  {
>> -     if (!test_bit(usage->hid, hi->input->absbit))
>> -             td->last_slot_field = usage->hid;
>> +     struct mt_fields *f = td->fields;
>
> And inserting td->last_field_index = field->index here.
>
>> +
>> +     if (f->length >= HID_MAX_FIELDS)
>> +             return;
>> +
>> +     f->usages[f->length++] = usage->hid;
>>  }
>>
>>  static int mt_input_mapping(struct hid_device *hdev, struct hid_input *hi,
>> @@ -330,7 +341,7 @@ static int mt_input_mapping(struct hid_device *hdev, struct hid_input *hi,
>>                               cls->sn_move);
>>                       /* touchscreen emulation */
>>                       set_abs(hi->input, ABS_X, field, cls->sn_move);
>> -                     set_last_slot_field(usage, td, hi);
>> +                     mt_store_field(usage, td, hi);
>>                       td->last_field_index = field->index;
>>                       return 1;
>>               case HID_GD_Y:
>> @@ -340,7 +351,7 @@ static int mt_input_mapping(struct hid_device *hdev, struct hid_input *hi,
>>                               cls->sn_move);
>>                       /* touchscreen emulation */
>>                       set_abs(hi->input, ABS_Y, field, cls->sn_move);
>> -                     set_last_slot_field(usage, td, hi);
>> +                     mt_store_field(usage, td, hi);
>>                       td->last_field_index = field->index;
>>                       return 1;
>>               }
>> @@ -349,24 +360,24 @@ static int mt_input_mapping(struct hid_device *hdev, struct hid_input *hi,
>>       case HID_UP_DIGITIZER:
>>               switch (usage->hid) {
>>               case HID_DG_INRANGE:
>> -                     set_last_slot_field(usage, td, hi);
>> +                     mt_store_field(usage, td, hi);
>>                       td->last_field_index = field->index;
>>                       return 1;
>>               case HID_DG_CONFIDENCE:
>> -                     set_last_slot_field(usage, td, hi);
>> +                     mt_store_field(usage, td, hi);
>>                       td->last_field_index = field->index;
>>                       return 1;
>>               case HID_DG_TIPSWITCH:
>>                       hid_map_usage(hi, usage, bit, max, EV_KEY, BTN_TOUCH);
>>                       input_set_capability(hi->input, EV_KEY, BTN_TOUCH);
>> -                     set_last_slot_field(usage, td, hi);
>> +                     mt_store_field(usage, td, hi);
>>                       td->last_field_index = field->index;
>>                       return 1;
>>               case HID_DG_CONTACTID:
>>                       if (!td->maxcontacts)
>>                               td->maxcontacts = MT_DEFAULT_MAXCONTACT;
>>                       input_mt_init_slots(hi->input, td->maxcontacts);
>> -                     td->last_slot_field = usage->hid;
>> +                     mt_store_field(usage, td, hi);
>>                       td->last_field_index = field->index;
>>                       td->touches_by_report++;
>>                       return 1;
>> @@ -375,7 +386,7 @@ static int mt_input_mapping(struct hid_device *hdev, struct hid_input *hi,
>>                                       EV_ABS, ABS_MT_TOUCH_MAJOR);
>>                       set_abs(hi->input, ABS_MT_TOUCH_MAJOR, field,
>>                               cls->sn_width);
>> -                     set_last_slot_field(usage, td, hi);
>> +                     mt_store_field(usage, td, hi);
>>                       td->last_field_index = field->index;
>>                       return 1;
>>               case HID_DG_HEIGHT:
>> @@ -385,7 +396,7 @@ static int mt_input_mapping(struct hid_device *hdev, struct hid_input *hi,
>>                               cls->sn_height);
>>                       input_set_abs_params(hi->input,
>>                                       ABS_MT_ORIENTATION, 0, 1, 0, 0);
>> -                     set_last_slot_field(usage, td, hi);
>> +                     mt_store_field(usage, td, hi);
>>                       td->last_field_index = field->index;
>>                       return 1;
>>               case HID_DG_TIPPRESSURE:
>> @@ -396,7 +407,7 @@ static int mt_input_mapping(struct hid_device *hdev, struct hid_input *hi,
>>                       /* touchscreen emulation */
>>                       set_abs(hi->input, ABS_PRESSURE, field,
>>                               cls->sn_pressure);
>> -                     set_last_slot_field(usage, td, hi);
>> +                     mt_store_field(usage, td, hi);
>>                       td->last_field_index = field->index;
>>                       return 1;
>>               case HID_DG_CONTACTCOUNT:
>> @@ -650,6 +661,16 @@ static void mt_post_parse_default_settings(struct mt_device *td)
>>       td->mtclass.quirks = quirks;
>>  }
>>
>> +static void mt_post_parse(struct mt_device *td)
>> +{
>> +     struct mt_fields *f = td->fields;
>> +
>> +     if (td->touches_by_report > 0) {
>> +             int field_count_per_touch = f->length / td->touches_by_report;
>> +             td->last_slot_field = f->usages[field_count_per_touch - 1]->hid;
>> +     }
>> +}
>> +
>>  static int mt_probe(struct hid_device *hdev, const struct hid_device_id *id)
>>  {
>>       int ret, i;
>> @@ -680,6 +701,13 @@ static int mt_probe(struct hid_device *hdev, const struct hid_device_id *id)
>>       td->maxcontact_report_id = -1;
>>       hid_set_drvdata(hdev, td);
>>
>> +     td->fields = kzalloc(sizeof(struct mt_fields), GFP_KERNEL);
>> +     if (!td->fields) {
>> +             dev_err(&hdev->dev, "cannot allocate multitouch fields data\n");
>> +             ret = -ENOMEM;
>> +             goto fail;
>> +     }
>> +
>
> This can be skipped.
>
>>       ret = hid_parse(hdev);
>>       if (ret != 0)
>>               goto fail;
>> @@ -688,6 +716,8 @@ static int mt_probe(struct hid_device *hdev, const struct hid_device_id *id)
>>       if (ret)
>>               goto fail;
>>
>> +     mt_post_parse(td);
>> +
>>       if (id->vendor == HID_ANY_ID && id->product == HID_ANY_ID)
>>               mt_post_parse_default_settings(td);
>>
>> @@ -705,9 +735,13 @@ static int mt_probe(struct hid_device *hdev, const struct hid_device_id *id)
>>       mt_set_maxcontacts(hdev);
>>       mt_set_input_mode(hdev);
>>
>> +     kfree(td->fields);
>> +     td->fields = NULL;
>> +
>
> Ditto.
>
>>       return 0;
>>
>>  fail:
>> +     kfree(td->fields);
>
> Ditto.
>
>>       kfree(td);
>>       return ret;
>>  }
>> --
>> 1.7.7.6
>>
>
> Thanks,
> Henrik
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