Re: [PATCH v2] HID: core: check whether usage page item is after usage id item

[Benjamin Tissoires <benjamin.tissoires@redhat.com>]

On Wed, Oct 9, 2019 at 2:54 PM Candle Sun <candlesea@gmail.com> wrote:
>
> From: Candle Sun <candle.sun@unisoc.com>
>
> Upstream commit 58e75155009c ("HID: core: move Usage Page concatenation
> to Main item") adds support for Usage Page item after Usage ID items
> (such as keyboards manufactured by Primax).
>
> Usage Page concatenation in Main item works well for following report
> descriptor patterns:
>
>     USAGE_PAGE (Keyboard)                   05 07
>     USAGE_MINIMUM (Keyboard LeftControl)    19 E0
>     USAGE_MAXIMUM (Keyboard Right GUI)      29 E7
>     LOGICAL_MINIMUM (0)                     15 00
>     LOGICAL_MAXIMUM (1)                     25 01
>     REPORT_SIZE (1)                         75 01
>     REPORT_COUNT (8)                        95 08
>     INPUT (Data,Var,Abs)                    81 02
>
> -------------
>
>     USAGE_MINIMUM (Keyboard LeftControl)    19 E0
>     USAGE_MAXIMUM (Keyboard Right GUI)      29 E7
>     LOGICAL_MINIMUM (0)                     15 00
>     LOGICAL_MAXIMUM (1)                     25 01
>     REPORT_SIZE (1)                         75 01
>     REPORT_COUNT (8)                        95 08
>     USAGE_PAGE (Keyboard)                   05 07
>     INPUT (Data,Var,Abs)                    81 02
>
> But it makes the parser act wrong for the following report
> descriptor pattern(such as some Gamepads):
>
>     USAGE_PAGE (Button)                     05 09
>     USAGE (Button 1)                        09 01
>     USAGE (Button 2)                        09 02
>     USAGE (Button 4)                        09 04
>     USAGE (Button 5)                        09 05
>     USAGE (Button 7)                        09 07
>     USAGE (Button 8)                        09 08
>     USAGE (Button 14)                       09 0E
>     USAGE (Button 15)                       09 0F
>     USAGE (Button 13)                       09 0D
>     USAGE_PAGE (Consumer Devices)           05 0C
>     USAGE (Back)                            0a 24 02
>     USAGE (HomePage)                        0a 23 02
>     LOGICAL_MINIMUM (0)                     15 00
>     LOGICAL_MAXIMUM (1)                     25 01
>     REPORT_SIZE (1)                         75 01
>     REPORT_COUNT (11)                       95 0B
>     INPUT (Data,Var,Abs)                    81 02
>
> With Usage Page concatenation in Main item, parser recognizes all the
> 11 Usages as consumer keys, it is not the HID device's real intention.
>
> This patch adds usage_page_last to flag whether Usage Page is after
> Usage ID items. usage_page_last is false default, it is set as true
> once Usage Page item is encountered and is reverted by next Usage ID
> item.
>
> Usage Page concatenation on the currently defined Usage Page will do
> firstly in Local parsing when Usage ID items encountered.
>
> When Main item is parsing, concatenation will do again with last
> defined Usage Page if usage_page_last flag is true.
>
> Signed-off-by: Candle Sun <candle.sun@unisoc.com>
> Signed-off-by: Nianfu Bai <nianfu.bai@unisoc.com>
> ---
> Changes in v2:
> - Update patch title
> - Add GET_COMPLETE_USAGE macro
> - Change the logic of checking whether to concatenate usage page again
>   in main parsing
> ---
>  drivers/hid/hid-core.c | 31 +++++++++++++++++++++++++------
>  include/linux/hid.h    |  1 +
>  2 files changed, 26 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
> index 3eaee2c..3394222 100644
> --- a/drivers/hid/hid-core.c
> +++ b/drivers/hid/hid-core.c
> @@ -35,6 +35,8 @@
>
>  #include "hid-ids.h"
>
> +#define GET_COMPLETE_USAGE(page, id) (((page) << 16) + ((id) & 0xffff))
> +
>  /*
>   * Version Information
>   */
> @@ -221,7 +223,15 @@ static int hid_add_usage(struct hid_parser *parser, unsigned usage, u8 size)
>                 hid_err(parser->device, "usage index exceeded\n");
>                 return -1;
>         }
> -       parser->local.usage[parser->local.usage_index] = usage;
> +
> +       if (size <= 2) {
> +               parser->local.usage_page_last = false;
> +               parser->local.usage[parser->local.usage_index] =
> +                       GET_COMPLETE_USAGE(parser->global.usage_page, usage);
> +       } else {
> +               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 ?
> @@ -366,6 +376,7 @@ static int hid_parser_global(struct hid_parser *parser, struct hid_item *item)
>
>         case HID_GLOBAL_ITEM_TAG_USAGE_PAGE:
>                 parser->global.usage_page = item_udata(item);
> +               parser->local.usage_page_last = true;
>                 return 0;
>
>         case HID_GLOBAL_ITEM_TAG_LOGICAL_MINIMUM:
> @@ -543,13 +554,21 @@ static int hid_parser_local(struct hid_parser *parser, struct hid_item *item)
>   * usage value."
>   */
>
> -static void hid_concatenate_usage_page(struct hid_parser *parser)
> +static void hid_concatenate_last_usage_page(struct hid_parser *parser)
>  {
>         int i;
> +       unsigned int usage;
> +       unsigned int usage_page = parser->global.usage_page;
> +
> +       if (!parser->local.usage_page_last)
> +               return;
>
>         for (i = 0; i < parser->local.usage_index; i++)
> -               if (parser->local.usage_size[i] <= 2)
> -                       parser->local.usage[i] += parser->global.usage_page << 16;
> +               if (parser->local.usage_size[i] <= 2) {
> +                       usage = parser->local.usage[i];
> +                       parser->local.usage[i] =
> +                               GET_COMPLETE_USAGE(usage_page, usage);
> +               }
>  }
>
>  /*
> @@ -561,7 +580,7 @@ static int hid_parser_main(struct hid_parser *parser, struct hid_item *item)
>         __u32 data;
>         int ret;
>
> -       hid_concatenate_usage_page(parser);
> +       hid_concatenate_last_usage_page(parser);
>
>         data = item_udata(item);
>
> @@ -772,7 +791,7 @@ static int hid_scan_main(struct hid_parser *parser, struct hid_item *item)
>         __u32 data;
>         int i;
>
> -       hid_concatenate_usage_page(parser);
> +       hid_concatenate_last_usage_page(parser);
>
>         data = item_udata(item);
>
> diff --git a/include/linux/hid.h b/include/linux/hid.h
> index cd41f20..2e0ea2f7 100644
> --- a/include/linux/hid.h
> +++ b/include/linux/hid.h
> @@ -412,6 +412,7 @@ struct hid_local {
>         unsigned usage_minimum;
>         unsigned delimiter_depth;
>         unsigned delimiter_branch;
> +       bool usage_page_last;      /* whether usage page is after usage id */

We don't need that extra flag:
if you just check on the last element, you can guess that information:

        if ((parser->local.usage[parser->local.usage_index - 1] &
HID_USAGE_PAGE) >> 16 == usage_page)
              return 0;

Let's see the next version before requesting too many changes.

And yes, I agree I need the hid-tools patches or I will not merge this
patch (and I will advise Jiri to not take it either).

Cheers,
Benjamin