Re: [PATCH 1/3] HID: Use existing parser for pre-scanning the reportdescriptors

From: Benjamin Tissoires
Date: Wed Aug 14 2013 - 11:09:26 EST

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On 13/08/13 20:37, Alexander Holler wrote:
> Am 13.08.2013 16:58, schrieb Benjamin Tissoires:
>> hid_scan_report() implements its own HID report descriptor parsing. It
>> was
>> fine until we added the SENSOR_HUB detection. It is going to be even
>> worse
>> with the detection of Win 8 certified touchscreen, as this detection
>> relies on a special feature and on the report_size and report_count
>> fields.
>
> Sorry, but I can't agree with your wording here.
>
> If you look at the if expression I've added to support HID sensor hubs,
> you will notice that the first expression was a test for the usage page
> of sensor hubs. That wasn't the first test by accident, instead I've
> choosen the order of those 4 tests very carefully to make the impact on
> the existing parsing of other HID devices very small. So it might not
> have be pleasing to your eyes, but it was for sure an appropriate solution.
>
> Anyway, I've tested your patch 1/3 on top of 3.11-rc5 here and the
> detection of sensor hubs doesn't work anymore with your patch applied.
> Up to now I only had a quick look at it, but it looks like the test in
> hid_scan_open_collection() isn't hit for my device.

Ok, I found the culprit (see below). Thanks for providing your report
descriptors (and sources), I managed to test the detection of your device.

>
> Another problem is that I don't have any commercial sensor hub and I'm
> therefor not a very relvant as tester (I've implemented the firmware for
> my HID (sensor hub) device too). Therefor I've added Srinivas Pandruvada
> to cc, because he's the only one I know who has HID sensor hubs.
>
> And, as said, I've implemented the other side here too, therefor I've
> added the descriptor I'm using below.
>
> Regards,
>
> Alexander Holler
>
>
> --my-descriptor--
> 0x05, 0x20, // HID_USAGE_PAGE_SENSOR
> 0xa1, 0x01, // COLLECTION (Application)
> 0x09, 0xa0, // HID_USAGE_SENSOR_CATEGORY_TIME
> 0xa1, 0x00, // COLLECTION (Physical)
> #ifndef USE_FULL_YEAR
> 0x75, 0x08, // REPORT_SIZE (8 bits)
> #endif
> 0x95, 0x01, // REPORT_COUNT (1)
> 0x85, HID_REPORT_ID_TIME, // REPORT_ID
>
> 0x0a, 0x21, 0x05, // USAGE (Year)
> #ifdef USE_FULL_YEAR
> 0x75, 0x10, // REPORT_SIZE (16 bits)
> #else
> 0x15, 0x00, // LOGICAL_MINIMUM (0) (Range is currently not
> specified in HUTRR39)
> 0x25, 0x63, // LOGICAL_MAXIMUM (99)
> #endif
> 0x65, 0x00, // UNIT (None)
> 0x81, 0x02, // INPUT (Data,Var,Abs)
>
> 0x0a, 0x22, 0x05, // USAGE (Month)
> #ifdef USE_FULL_YEAR
> 0x75, 0x08, // REPORT_SIZE (8 bits)
> #endif
> 0x15, 0x01, // LOGICAL_MINIMUM (1)
> 0x25, 0x0c, // LOGICAL_MAXIMUM (12)
> 0x65, 0x00, // UNIT (None)
> 0x81, 0x02, // INPUT (Data,Var,Abs)
>
> 0x0a, 0x23, 0x05, // USAGE (Day)
> 0x15, 0x01, // LOGICAL_MINIMUM (1)
> 0x25, 0x1f, // LOGICAL_MAXIMUM (31)
> 0x65, 0x00, // UNIT (None)
> 0x81, 0x02, // INPUT (Data,Var,Abs)
>
> 0x0a, 0x24, 0x05, // USAGE (Day of Week)
> 0x15, 0x00, // LOGICAL_MINIMUM (0)
> 0x25, 0x06, // LOGICAL_MAXIMUM (6)
> 0xa1, 0x02, // COLLECTION (Logical)
> 0x0a, 0xc0, 0x08, // Day of Week: Sunday
> 0x0a, 0xc1, 0x08, // Day of Week: Monday
> 0x0a, 0xc2, 0x08, // Day of Week: Tuesday
> 0x0a, 0xc3, 0x08, // Day of Week: Wednesday
> 0x0a, 0xc4, 0x08, // Day of Week: Thursday
> 0x0a, 0xc5, 0x08, // Day of Week: Friday
> 0x0a, 0xc6, 0x08, // Day of Week: Saturday
> 0x81, 0x02, // INPUT (Const,Arr,Abs)
> 0xc0, // END_COLLECTION
>
> 0x0a, 0x25, 0x05, // USAGE (Hour)
> 0x15, 0x00, // LOGICAL_MINIMUM (0)
> 0x25, 0x17, // LOGICAL_MAXIMUM (23)
> 0x65, 0x00, // UNIT (None)
> 0x81, 0x02, // INPUT (Data,Var,Abs)
>
> 0x0a, 0x26, 0x05, // USAGE (Minute)
> 0x15, 0x00, // LOGICAL_MINIMUM (0)
> 0x25, 0x3b, // LOGICAL_MAXIMUM (59)
> 0x65, 0x00, // UNIT (None)
> 0x81, 0x02, // INPUT (Data,Var,Abs)
>
> 0x0a, 0x27, 0x05, // USAGE (Second)
> 0x15, 0x00, // LOGICAL_MINIMUM (0)
> 0x25, 0x3b, // LOGICAL_MAXIMUM (59)
> 0x65, 0x00, // UNIT (None)
> //0x66, 0x10, 0x01, // UNIT (second)
> 0x81, 0x02, // INPUT (Data,Var,Abs)
>
> 0x0a, 0x28, 0x05, // USAGE (Millisecond)
> 0x75, 0x10, // REPORT_SIZE (16 bits)
> 0x65, 0x00, // UNIT (None)
> 0x81, 0x02, // INPUT (Data,Var,Abs)
>
> 0xc0, // END_COLLECTION
> 0xc0, // END_COLLECTION
> --my-descriptor--
>
>>
>> We can use the existing HID parser in hid-core for hid_scan_report()
>> by re-using the code from hid_open_report(). hid_parser_global,
>> hid_parser_local and hid_parser_reserved does not have any side effects.
>> We just need to reimplement the MAIN_ITEM callback to have a proper
>> parsing without side effects.
>>
>> Instead of directly overwriting the ->group field, this patch introduce
>> a ->flags field and then decide which group the device belongs to,
>> depending on the whole parsing (not just the local item). This will be
>> useful for Win 8 multitouch devices, which are multitouch devices and
>> Win 8 certified (so 2 flags to check).
>>
>> Signed-off-by: Benjamin Tissoires <benjamin.tissoires@xxxxxxxxxx>
>> ---
>> drivers/hid/hid-core.c | 131
>> +++++++++++++++++++++++++++++++++++--------------
>> include/linux/hid.h | 4 ++
>> 2 files changed, 97 insertions(+), 38 deletions(-)
>>
>> diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
>> index 3efe19f..d8cdb0a 100644
>> --- a/drivers/hid/hid-core.c
>> +++ b/drivers/hid/hid-core.c
>> @@ -677,10 +677,49 @@ static u8 *fetch_item(__u8 *start, __u8 *end,
>> struct hid_item *item)
>> return NULL;
>> }
>>
>> -static void hid_scan_usage(struct hid_device *hid, u32 usage)
>> +static void hid_scan_input_usage(struct hid_parser *parser, u32 usage)
>> {
>> if (usage == HID_DG_CONTACTID)
>> - hid->group = HID_GROUP_MULTITOUCH;
>> + parser->flags |= HID_FLAG_MULTITOUCH;
>> +}
>> +
>> +static void hid_scan_open_collection(struct hid_parser *parser,
>> unsigned type)
>> +{
>> + if (parser->global.usage_page == HID_UP_SENSOR &&

HID_UP_SENSOR is actually 0x00200000, and parser->global.usage_page
contains the raw value 0x0020... Moving HID_UP_SENSOR 16 bits to the
right makes the test working, and your sensor device correctly tagged.

Cheers,
Benjamin

>> + type == HID_COLLECTION_PHYSICAL)
>> + parser->flags |= HID_FLAG_SENSOR_HUB;
>> +}
>> +
>> +static int hid_scan_main(struct hid_parser *parser, struct hid_item
>> *item)
>> +{
>> + __u32 data;
>> + int i;
>> +
>> + data = item_udata(item);
>> +
>> + switch (item->tag) {
>> + case HID_MAIN_ITEM_TAG_BEGIN_COLLECTION:
>> + hid_scan_open_collection(parser, data & 0xff);
>> + break;
>> + case HID_MAIN_ITEM_TAG_END_COLLECTION:
>> + break;
>> + case HID_MAIN_ITEM_TAG_INPUT:
>> + for (i = 0; i < parser->local.usage_index; i++)
>> + hid_scan_input_usage(parser, parser->local.usage[i]);
>> + break;
>> + case HID_MAIN_ITEM_TAG_OUTPUT:
>> + break;
>> + case HID_MAIN_ITEM_TAG_FEATURE:
>> + break;
>> + default:
>> + hid_err(parser->device, "unknown main item tag 0x%x\n",
>> + item->tag);
>> + }
>> +
>> + /* Reset the local parser environment */
>> + memset(&parser->local, 0, sizeof(parser->local));
>> +
>> + return 0;
>> }
>>
>> /*
>> @@ -690,49 +729,65 @@ static void hid_scan_usage(struct hid_device
>> *hid, u32 usage)
>> */
>> static int hid_scan_report(struct hid_device *hid)
>> {
>> - unsigned int page = 0, delim = 0;
>> + struct hid_parser *parser;
>> + struct hid_item item;
>> __u8 *start = hid->dev_rdesc;
>> __u8 *end = start + hid->dev_rsize;
>> - unsigned int u, u_min = 0, u_max = 0;
>> - struct hid_item item;
>> + int ret;
>> + static int (*dispatch_type[])(struct hid_parser *parser,
>> + struct hid_item *item) = {
>> + hid_scan_main,
>> + hid_parser_global,
>> + hid_parser_local,
>> + hid_parser_reserved
>> + };
>>
>> - hid->group = HID_GROUP_GENERIC;
>> + parser = vzalloc(sizeof(struct hid_parser));
>> + if (!parser)
>> + return -ENOMEM;
>> +
>> + parser->device = hid;
>> +
>> + ret = -EINVAL;
>> while ((start = fetch_item(start, end, &item)) != NULL) {
>> - if (item.format != HID_ITEM_FORMAT_SHORT)
>> - return -EINVAL;
>> - if (item.type == HID_ITEM_TYPE_GLOBAL) {
>> - if (item.tag == HID_GLOBAL_ITEM_TAG_USAGE_PAGE)
>> - page = item_udata(&item) << 16;
>> - } else if (item.type == HID_ITEM_TYPE_LOCAL) {
>> - if (delim > 1)
>> - break;
>> - u = item_udata(&item);
>> - if (item.size <= 2)
>> - u += page;
>> - switch (item.tag) {
>> - case HID_LOCAL_ITEM_TAG_DELIMITER:
>> - delim += !!u;
>> - break;
>> - case HID_LOCAL_ITEM_TAG_USAGE:
>> - hid_scan_usage(hid, u);
>> - break;
>> - case HID_LOCAL_ITEM_TAG_USAGE_MINIMUM:
>> - u_min = u;
>> - break;
>> - case HID_LOCAL_ITEM_TAG_USAGE_MAXIMUM:
>> - u_max = u;
>> - for (u = u_min; u <= u_max; u++)
>> - hid_scan_usage(hid, u);
>> - break;
>> +
>> + if (item.format != HID_ITEM_FORMAT_SHORT) {
>> + hid_err(hid, "unexpected long global item\n");
>> + goto out;
>> + }
>> +
>> + if (dispatch_type[item.type](parser, &item)) {
>> + hid_err(hid, "item %u %u %u %u parsing failed\n",
>> + item.format, (unsigned)item.size,
>> + (unsigned)item.type, (unsigned)item.tag);
>> + goto out;
>> + }
>> +
>> + if (start == end) {
>> + if (parser->local.delimiter_depth) {
>> + hid_err(hid, "unbalanced delimiter at end of report
>> description\n");
>> + goto out;
>> }
>> - } else if (page == HID_UP_SENSOR &&
>> - item.type == HID_ITEM_TYPE_MAIN &&
>> - item.tag == HID_MAIN_ITEM_TAG_BEGIN_COLLECTION &&
>> - (item_udata(&item) & 0xff) == HID_COLLECTION_PHYSICAL)
>> - hid->group = HID_GROUP_SENSOR_HUB;
>> + ret = 0;
>> + goto out;
>> + }
>> }
>>
>> - return 0;
>> + hid_err(hid, "item fetching failed at offset %d\n", (int)(end -
>> start));
>> +out:
>> + switch (parser->flags) {
>> + case HID_FLAG_MULTITOUCH:
>> + hid->group = HID_GROUP_MULTITOUCH;
>> + break;
>> + case HID_FLAG_SENSOR_HUB:
>> + hid->group = HID_GROUP_SENSOR_HUB;
>> + break;
>> + default:
>> + hid->group = HID_GROUP_GENERIC;
>> + }
>> +
>> + vfree(parser);
>> + return ret;
>> }
>>
>> /**
>> diff --git a/include/linux/hid.h b/include/linux/hid.h
>> index 5a4e789..7d823db 100644
>> --- a/include/linux/hid.h
>> +++ b/include/linux/hid.h
>> @@ -533,6 +533,9 @@ static inline void hid_set_drvdata(struct
>> hid_device *hdev, void *data)
>> #define HID_GLOBAL_STACK_SIZE 4
>> #define HID_COLLECTION_STACK_SIZE 4
>>
>> +#define HID_FLAG_MULTITOUCH 0x0001
>> +#define HID_FLAG_SENSOR_HUB 0x0002
>> +
>> struct hid_parser {
>> struct hid_global global;
>> struct hid_global global_stack[HID_GLOBAL_STACK_SIZE];
>> @@ -541,6 +544,7 @@ struct hid_parser {
>> unsigned collection_stack[HID_COLLECTION_STACK_SIZE];
>> unsigned collection_stack_ptr;
>> struct hid_device *device;
>> + unsigned flags;
>> };
>>
>> struct hid_class_descriptor {
>>
>

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Next message: Julia Lawall: "Re: question about netif_rx"
Previous message: Kishon Vijay Abraham I: "Re: [PATCH 01/15] drivers: phy: add generic PHY framework"
In reply to: Alexander Holler: "Re: [PATCH 1/3] HID: Use existing parser for pre-scanning the reportdescriptors"
Next in thread: Srinivas Pandruvada: "Re: [PATCH 1/3] HID: Use existing parser for pre-scanning the reportdescriptors"
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