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

From: Candle Sun
Date: Wed Oct 09 2019 - 23:06:05 EST

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On Thu, Oct 10, 2019 at 1:01 AM Nicolas Saenz Julienne
<nsaenzjulienne@xxxxxxx> wrote:
>
> On Wed, 2019-10-09 at 20:53 +0800, Candle Sun wrote:
> > From: Candle Sun <candle.sun@xxxxxxxxxx>
> >
> > 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.
>
> Functionally I think this is the right approach. Sadly I don't have access to
> any Primax device anymore so I can't test it. But I suggest you update
> hid-tools' parser and add a new unit test to verify we aren't missing anything.
>
> You can base your code on this:
>
> https://gitlab.freedesktop.org/libevdev/hid-tools/merge_requests/37/commits
>

Thanks Nicolas. I will check and try to do it.

Candle

> > Signed-off-by: Candle Sun <candle.sun@xxxxxxxxxx>
> > Signed-off-by: Nianfu Bai <nianfu.bai@xxxxxxxxxx>
> > ---
> > 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))
>
> Not sure I like the macro. I'd rather have the explicit code. That said, lets
> see what Benjamin has to say.
>
> > +
> > /*
> > * 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."
> > */
>
> I'd expand the comment above to further explain what we're doing here.
>

OK, some comment here is better, I will add it.

Candle

> >
> > -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++)
>
> Technically correct but it's preferred if you use braces here.
>

Nicolas, do you mean this:

@@ -563,12 +563,13 @@ static void
hid_concatenate_last_usage_page(struct hid_parser *parser)
if (!parser->local.usage_page_last)
return;

- for (i = 0; i < parser->local.usage_index; i++)
+ for (i = 0; i < parser->local.usage_index; i++) {
if (parser->local.usage_size[i] <= 2) {
usage = parser->local.usage[i];
parser->local.usage[i] =
GET_COMPLETE_USAGE(usage_page, usage);
}
+ }
}

Candle

> > - 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 */
> > };
> >
> > /*
>
> Regards,
> Nicolas
>

Next message: Paul E. McKenney: "Re: [PATCH] rcu: Fix data-race due to atomic_t copy-by-value"
Previous message: Tuowen Zhao: "[PATCH v3 2/2] mfd: intel-lpss: use devm_ioremap_uc for MMIO"
In reply to: Candle Sun: "Re: [PATCH v2] HID: core: check whether usage page item is after usage id item"
Next in thread: Nicolas Saenz Julienne: "Re: [PATCH v2] HID: core: check whether usage page item is after usage id item"
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