[PATCH 1/3] HID: Use existing parser for pre-scanning the report descriptors
From: Benjamin Tissoires
Date: Tue Aug 13 2013 - 10:59:13 EST
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.
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 &&
+ 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 {
--
1.8.3.1
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/