Hi Nicolas,
On Tue, Mar 12, 2019 at 10:37 AM Nicolas Saenz Julienne
<nsaenzjulienne@xxxxxxx> wrote:
>
> As seen on some USB wireless keyboards manufactured by Primax, the HID
> parser was using some assumptions that are not always true. In this case
> it's s the fact that, inside the scope of a main item, an Usage Page
> will always precede an Usage.
>
> The spec is not pretty clear as 6.2.2.7 states "Any usage that follows
> is interpreted as a Usage ID and concatenated with the Usage Page".
> While 6.2.2.8 states "When the parser encounters a main item it
> concatenates the last declared Usage Page with a Usage to form a
> complete usage value." Being somewhat contradictory it was decided to
> match Window's implementation, which follows 6.2.2.8.
>
> In summary, the patch moves the Usage Page concatenation from the local
> item parsing function to the main item parsing function.
>
> Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@xxxxxxx>
> ---
Patch looks good to me.
Terry, did you have time to review it?
Cheers,
Benjamin
>
> Note: A PR in hid-tools shoud show up anytime soon
>
> drivers/hid/hid-core.c | 30 ++++++++++++++++++------------
> include/linux/hid.h | 1 +
> 2 files changed, 19 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
> index 9993b692598f..158468ef23a6 100644
> --- a/drivers/hid/hid-core.c
> +++ b/drivers/hid/hid-core.c
> @@ -218,13 +218,14 @@ static unsigned hid_lookup_collection(struct hid_parser *parser, unsigned type)
> * Add a usage to the temporary parser table.
> */
>
> -static int hid_add_usage(struct hid_parser *parser, unsigned usage)
> +static int hid_add_usage(struct hid_parser *parser, unsigned usage, __u8 size)
> {
> if (parser->local.usage_index >= HID_MAX_USAGES) {
> hid_err(parser->device, "usage index exceeded\n");
> return -1;
> }
> parser->local.usage[parser->local.usage_index] = usage;
> + parser->local.usage_size[parser->local.usage_index] = size;
> parser->local.collection_index[parser->local.usage_index] =
> parser->collection_stack_ptr ?
> parser->collection_stack[parser->collection_stack_ptr - 1] : 0;
> @@ -486,10 +487,7 @@ static int hid_parser_local(struct hid_parser *parser, struct hid_item *item)
> return 0;
> }
>
> - if (item->size <= 2)
> - data = (parser->global.usage_page << 16) + data;
> -
> - return hid_add_usage(parser, data);
> + return hid_add_usage(parser, data, item->size);
>
> case HID_LOCAL_ITEM_TAG_USAGE_MINIMUM:
>
> @@ -498,9 +496,6 @@ static int hid_parser_local(struct hid_parser *parser, struct hid_item *item)
> return 0;
> }
>
> - if (item->size <= 2)
> - data = (parser->global.usage_page << 16) + data;
> -
> parser->local.usage_minimum = data;
> return 0;
>
> @@ -511,9 +506,6 @@ static int hid_parser_local(struct hid_parser *parser, struct hid_item *item)
> return 0;
> }
>
> - if (item->size <= 2)
> - data = (parser->global.usage_page << 16) + data;
> -
> count = data - parser->local.usage_minimum;
> if (count + parser->local.usage_index >= HID_MAX_USAGES) {
> /*
> @@ -533,7 +525,7 @@ static int hid_parser_local(struct hid_parser *parser, struct hid_item *item)
> }
>
> for (n = parser->local.usage_minimum; n <= data; n++)
> - if (hid_add_usage(parser, n)) {
> + if (hid_add_usage(parser, n, item->size)) {
> dbg_hid("hid_add_usage failed\n");
> return -1;
> }
> @@ -553,8 +545,22 @@ static int hid_parser_local(struct hid_parser *parser, struct hid_item *item)
>
> static int hid_parser_main(struct hid_parser *parser, struct hid_item *item)
> {
> + unsigned int usages;
> __u32 data;
> int ret;
> + int i;
> +
> + usages = max_t(unsigned, parser->local.usage_index,
> + parser->global.report_count);
> +
> + /*
> + * As per specification, 6.2.2.8:
> + * "When the parser encounters a main item it concatenates the last
> + * declared Usage Page with a Usage to form a complete usage value."
> + */
> + for (i = 0; i < usages; i++)
> + if (parser->local.usage_size[i] <= 2)
> + parser->local.usage[i] += parser->global.usage_page << 16;
>
> data = item_udata(item);
>
> diff --git a/include/linux/hid.h b/include/linux/hid.h
> index f9707d1dcb58..d1fb4b678873 100644
> --- a/include/linux/hid.h
> +++ b/include/linux/hid.h
> @@ -417,6 +417,7 @@ struct hid_global {
>
> struct hid_local {
> unsigned usage[HID_MAX_USAGES]; /* usage array */
> + __u8 usage_size[HID_MAX_USAGES]; /* usage size array */
> unsigned collection_index[HID_MAX_USAGES]; /* collection index array */
> unsigned usage_index;
> unsigned usage_minimum;
> --
> 2.21.0
>
