HID: Use hid_parser for pre-scanning the report descriptors

The Win 8 detection is sufficiently complex to warrant use of the full
parser code, in spite of the inferred memory usage. Therefore, 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@redhat.com>
Reviewed-by: Henrik Rydberg <rydberg@euromail.se>
Tested-by: Srinivas Pandruvada<srinivas.pandruvada@linux.intel.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
index e39dac6..ddd95f3 100644 (file)
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -677,12 +677,52 @@ 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;
+       }
+
+       /* 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 +730,34 @@ 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
+       };
+
+       parser = vzalloc(sizeof(struct hid_parser));
+       if (!parser)
+               return -ENOMEM;
 
+       parser->device = hid;
        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;
-       }
 
+       /*
+        * 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;
 }