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Message-ID: <CAN+gG=Ft=wer1GAiR9W8z7xjujRuqh13co35X-eA2PpSppCZRA@mail.gmail.com>
Date: Thu, 22 Aug 2013 10:31:57 +0200
From: Benjamin Tissoires <benjamin.tissoires@...il.com>
To: Henrik Rydberg <rydberg@...omail.se>
Cc: Benjamin Tissoires <benjamin.tissoires@...hat.com>,
Jiri Kosina <jkosina@...e.cz>,
Stephane Chatty <chatty@...c.fr>,
Alexander Holler <holler@...oftware.de>,
Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
linux-input <linux-input@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/3] HID: Use hid_parser for pre-scanning the report descriptors
Hi Henrik,
On Wed, Aug 21, 2013 at 8:15 PM, Henrik Rydberg <rydberg@...omail.se> wrote:
> Hi Benjamin,
>
> this looks pretty good to me, just a few nitpicks below.
>
>> hid_scan_report() implements its own HID report descriptor parsing. It is
>> going to be really bad 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.
>
> How about 'The Win 8 detection is sufficiently complex to warrant use
> of the full parser code, in spite of the inferred memory
> usage. Therefore...'
>
Sure. Will change in v3.
>>
>> 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.
>>
>> Signed-off-by: Benjamin Tissoires <benjamin.tissoires@...hat.com>
>> ---
>>
>> changes in v2:
>> - moved "flags" processing in patch 2/3 (so use hid->group in this patch)
>> - hid_scan_report() is less verbose when errors are found in the descriptor
>> - hid_scan_report() is tolerant to parsing errors
>> - fixed usage_page handling in hid_scan_collection(), which fixes sensors detection
>> - amended commit message
>>
>> drivers/hid/hid-core.c | 106 +++++++++++++++++++++++++++++++------------------
>> 1 file changed, 67 insertions(+), 39 deletions(-)
>>
>> diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
>> index 3efe19f..e072b15 100644
>> --- a/drivers/hid/hid-core.c
>> +++ b/drivers/hid/hid-core.c
>> @@ -677,12 +677,55 @@ 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)
>> {
>> + struct hid_device *hid = parser->device;
>> +
>> if (usage == HID_DG_CONTACTID)
>> hid->group = HID_GROUP_MULTITOUCH;
>> }
>>
>> +static void hid_scan_collection(struct hid_parser *parser, unsigned type)
>> +{
>> + struct hid_device *hid = parser->device;
>> +
>> + if (((parser->global.usage_page << 16) == HID_UP_SENSOR) &&
>> + type == HID_COLLECTION_PHYSICAL)
>> + hid->group = HID_GROUP_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_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);
>
> Looks this this message is a duplicate as well.
oops, forgot to remove it :)
Cheers,
Benjamin
>
>> + }
>> +
>> + /* Reset the local parser environment */
>> + memset(&parser->local, 0, sizeof(parser->local));
>> +
>> + return 0;
>> +}
>> +
>> /*
>> * Scan a report descriptor before the device is added to the bus.
>> * Sets device groups and other properties that determine what driver
>> @@ -690,48 +733,33 @@ 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;
>> + 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;
>> - 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;
>> - }
>> - } 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;
>> - }
>> + parser = vzalloc(sizeof(struct hid_parser));
>> + if (!parser)
>> + return -ENOMEM;
>> +
>> + parser->device = hid;
>> +
>> + /*
>> + * The parsing is simpler than the one in hid_open_report() as we should
>> + * be robust against hid errors. Those errors will be raised by
>> + * hid_open_report() anyway.
>> + */
>> + while ((start = fetch_item(start, end, &item)) != NULL)
>> + dispatch_type[item.type](parser, &item);
>>
>> + vfree(parser);
>> return 0;
>> }
>>
>> --
>> 1.8.3.1
>>
>
> Thanks,
> Henrik
--
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