linux-kernel - [PATCH v2 01/12] HID: core: statically allocate read buffers

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Date:   Thu,  3 Feb 2022 15:32:15 +0100
From:   Benjamin Tissoires <benjamin.tissoires@...hat.com>
To:     Jiri Kosina <jikos@...nel.org>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Jonathan Corbet <corbet@....net>,
        Ahelenia Ziemiańska 
        <nabijaczleweli@...ijaczleweli.xyz>,
        Ping Cheng <pinglinux@...il.com>,
        Aaron Armstrong Skomra <skomra@...il.com>,
        Jason Gerecke <killertofu@...il.com>,
        Peter Hutterer <peter.hutterer@...-t.net>
Cc:     linux-input@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>
Subject: [PATCH v2 01/12] HID: core: statically allocate read buffers

This is a preparation patch for rethinking the generic processing
of HID reports.

We can actually pre-allocate all of our memory instead of dynamically
allocating/freeing it whenever we parse a report.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@...hat.com>
---
 drivers/hid/hid-core.c | 12 +++++-------
 include/linux/hid.h    |  1 +
 2 files changed, 6 insertions(+), 7 deletions(-)

diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
index f1aed5bbd000..75e7b8447bf7 100644
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -101,7 +101,7 @@ static struct hid_field *hid_register_field(struct hid_report *report, unsigned
 
 	field = kzalloc((sizeof(struct hid_field) +
 			 usages * sizeof(struct hid_usage) +
-			 usages * sizeof(unsigned)), GFP_KERNEL);
+			 2 * usages * sizeof(unsigned int)), GFP_KERNEL);
 	if (!field)
 		return NULL;
 
@@ -109,6 +109,7 @@ static struct hid_field *hid_register_field(struct hid_report *report, unsigned
 	report->field[field->index] = field;
 	field->usage = (struct hid_usage *)(field + 1);
 	field->value = (s32 *)(field->usage + usages);
+	field->new_value = (s32 *)(field->value + usages);
 	field->report = report;
 
 	return field;
@@ -1541,9 +1542,8 @@ static void hid_input_field(struct hid_device *hid, struct hid_field *field,
 	__s32 max = field->logical_maximum;
 	__s32 *value;
 
-	value = kmalloc_array(count, sizeof(__s32), GFP_ATOMIC);
-	if (!value)
-		return;
+	value = field->new_value;
+	memset(value, 0, count * sizeof(__s32));
 
 	for (n = 0; n < count; n++) {
 
@@ -1557,7 +1557,7 @@ static void hid_input_field(struct hid_device *hid, struct hid_field *field,
 		    value[n] >= min && value[n] <= max &&
 		    value[n] - min < field->maxusage &&
 		    field->usage[value[n] - min].hid == HID_UP_KEYBOARD + 1)
-			goto exit;
+			return;
 	}
 
 	for (n = 0; n < count; n++) {
@@ -1581,8 +1581,6 @@ static void hid_input_field(struct hid_device *hid, struct hid_field *field,
 	}
 
 	memcpy(field->value, value, count * sizeof(__s32));
-exit:
-	kfree(value);
 }
 
 /*
diff --git a/include/linux/hid.h b/include/linux/hid.h
index 7487b0586fe6..3fbfe0986659 100644
--- a/include/linux/hid.h
+++ b/include/linux/hid.h
@@ -476,6 +476,7 @@ struct hid_field {
 	unsigned  report_count;		/* number of this field in the report */
 	unsigned  report_type;		/* (input,output,feature) */
 	__s32    *value;		/* last known value(s) */
+	__s32    *new_value;		/* newly read value(s) */
 	__s32     logical_minimum;
 	__s32     logical_maximum;
 	__s32     physical_minimum;
-- 
2.33.1