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>

1 files changed, 64 insertions, 38 deletions

diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
index e39dac68063c..ddd95f3e33c0 100644
--- 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;
 }