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Date: Tue, 26 Mar 2019 22:43:24 +0000
From: "Junge, Terry" <terry.junge@...y.com>
To: Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
Jiri Kosina <jikos@...nel.org>,
Benjamin Tissoires <benjamin.tissoires@...hat.com>
CC: "oneukum@...e.de" <oneukum@...e.de>,
"linux-input@...r.kernel.org" <linux-input@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v3] HID: core: move Usage Page concatenation to Main item
Hi Nicolas,
This patch looks good except for one comment/question below.
Thanks,
Terry
On Tuesday, March 26, 2019 1:04 PM Nicolas Saenz Julienne <nsaenzjulienne@...e.de> 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@...e.de>
>---
>
>v2->v3: - Update patch title
>
>v1->v2: - Add usage concatenation to hid_scan_main()
> - Rework tests in hid-tools, making sure no-one is failing
>
> drivers/hid/hid-core.c | 40 ++++++++++++++++++++++++++++------------
> include/linux/hid.h | 1 +
> 2 files changed, 29 insertions(+), 12 deletions(-)
>
>diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c index
>9993b692598f..40c836ce3248 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;
> }
>@@ -547,6 +539,26 @@ static int hid_parser_local(struct hid_parser *parser,
>struct hid_item *item)
> return 0;
> }
>
>+/*
>+ * Concatenate Usage Pages into Usages where relevant:
>+ * 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."
>+ */
>+
>+static void hid_concatenate_usage_page(struct hid_parser *parser) {
>+ unsigned usages;
>+ int i;
>+
>+ usages = max_t(unsigned, parser->local.usage_index,
>+ parser->global.report_count);
I don't think we need to worry about global.report_count here,
just concatenate for the usages currently in the local queue so could
this be simplified by removing usages and just using local.usage_index?
for (i = 0; i < local.usage_index; i++)
>+
>+ for (i = 0; i < usages; i++)
>+ if (parser->local.usage_size[i] <= 2)
>+ parser->local.usage[i] += parser->global.usage_page
><< 16; }
>+
> /*
> * Process a main item.
> */
>@@ -556,6 +568,8 @@ static int hid_parser_main(struct hid_parser *parser,
>struct hid_item *item)
> __u32 data;
> int ret;
>
>+ hid_concatenate_usage_page(parser);
>+
> data = item_udata(item);
>
> switch (item->tag) {
>@@ -765,6 +779,8 @@ static int hid_scan_main(struct hid_parser *parser,
>struct hid_item *item)
> __u32 data;
> int i;
>
>+ hid_concatenate_usage_page(parser);
>+
> data = item_udata(item);
>
> switch (item->tag) {
>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
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