HID: i2c-hid: override HID descriptors for certain devices

A particular touchpad (SIPODEV SP1064) refuses to supply the HID
descriptors. This patch provides the framework for overriding these
descriptors based on DMI data. It also includes the descriptors for
said touchpad, which were extracted by listening to the traffic of the
windows filter driver, as well as the DMI data for the laptops known
to use this device.

Relevant Bug: https://bugzilla.redhat.com/show_bug.cgi?id=1526312

Cc: Hans de Goede <hdegoede@redhat.com>
Reported-and-tested-by: ahormann@gmx.net
Reported-and-tested-by: Bruno Jesus <bruno.fl.jesus@gmail.com>
Reported-and-tested-by: Dietrich <enaut.w@googlemail.com>
Reported-and-tested-by: kloxdami@yahoo.com
Signed-off-by: Julian Sax <jsbc@gmx.de>
Reviewed-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/i2c-hid/Makefile

@@ -3,3 +3,6 @@
 #
 
 obj-$(CONFIG_I2C_HID)				+= i2c-hid.o
+
+i2c-hid-objs					=  i2c-hid-core.o
+i2c-hid-$(CONFIG_DMI)				+= i2c-hid-dmi-quirks.o

drivers/hid/i2c-hid/i2c-hid.c → drivers/hid/i2c-hid/i2c-hid-core.c

@@ -43,6 +43,7 @@
 #include <linux/platform_data/i2c-hid.h>
 
 #include "../hid-ids.h"
+#include "i2c-hid.h"
 
 /* quirks to control the device */
 #define I2C_HID_QUIRK_SET_PWR_WAKEUP_DEV	BIT(0)
@@ -669,6 +670,7 @@ static int i2c_hid_parse(struct hid_device *hid)
 	char *rdesc;
 	int ret;
 	int tries = 3;
+	char *use_override;
 
 	i2c_hid_dbg(ihid, "entering %s\n", __func__);
 
@@ -687,26 +689,37 @@ static int i2c_hid_parse(struct hid_device *hid)
 	if (ret)
 		return ret;
 
-	rdesc = kzalloc(rsize, GFP_KERNEL);
+	use_override = i2c_hid_get_dmi_hid_report_desc_override(client->name,
+								&rsize);
 
-	if (!rdesc) {
-		dbg_hid("couldn't allocate rdesc memory\n");
-		return -ENOMEM;
-	}
-
-	i2c_hid_dbg(ihid, "asking HID report descriptor\n");
-
-	ret = i2c_hid_command(client, &hid_report_descr_cmd, rdesc, rsize);
-	if (ret) {
-		hid_err(hid, "reading report descriptor failed\n");
-		kfree(rdesc);
-		return -EIO;
+	if (use_override) {
+		rdesc = use_override;
+		i2c_hid_dbg(ihid, "Using a HID report descriptor override\n");
+	} else {
+		rdesc = kzalloc(rsize, GFP_KERNEL);
+
+		if (!rdesc) {
+			dbg_hid("couldn't allocate rdesc memory\n");
+			return -ENOMEM;
+		}
+
+		i2c_hid_dbg(ihid, "asking HID report descriptor\n");
+
+		ret = i2c_hid_command(client, &hid_report_descr_cmd,
+				      rdesc, rsize);
+		if (ret) {
+			hid_err(hid, "reading report descriptor failed\n");
+			kfree(rdesc);
+			return -EIO;
+		}
 	}
 
 	i2c_hid_dbg(ihid, "Report Descriptor: %*ph\n", rsize, rdesc);
 
 	ret = hid_parse_report(hid, rdesc, rsize);
-	kfree(rdesc);
+	if (!use_override)
+		kfree(rdesc);
+
 	if (ret) {
 		dbg_hid("parsing report descriptor failed\n");
 		return ret;
@@ -833,12 +846,19 @@ static int i2c_hid_fetch_hid_descriptor(struct i2c_hid *ihid)
 	int ret;
 
 	/* i2c hid fetch using a fixed descriptor size (30 bytes) */
-	i2c_hid_dbg(ihid, "Fetching the HID descriptor\n");
-	ret = i2c_hid_command(client, &hid_descr_cmd, ihid->hdesc_buffer,
-				sizeof(struct i2c_hid_desc));
-	if (ret) {
-		dev_err(&client->dev, "hid_descr_cmd failed\n");
-		return -ENODEV;
+	if (i2c_hid_get_dmi_i2c_hid_desc_override(client->name)) {
+		i2c_hid_dbg(ihid, "Using a HID descriptor override\n");
+		ihid->hdesc =
+			*i2c_hid_get_dmi_i2c_hid_desc_override(client->name);
+	} else {
+		i2c_hid_dbg(ihid, "Fetching the HID descriptor\n");
+		ret = i2c_hid_command(client, &hid_descr_cmd,
+				      ihid->hdesc_buffer,
+				      sizeof(struct i2c_hid_desc));
+		if (ret) {
+			dev_err(&client->dev, "hid_descr_cmd failed\n");
+			return -ENODEV;
+		}
 	}
 
 	/* Validate the length of HID descriptor, the 4 first bytes:

drivers/hid/i2c-hid/i2c-hid.h

+/* SPDX-License-Identifier: GPL-2.0+ */
+
+#ifndef I2C_HID_H
+#define I2C_HID_H
+
+
+#ifdef CONFIG_DMI
+struct i2c_hid_desc *i2c_hid_get_dmi_i2c_hid_desc_override(uint8_t *i2c_name);
+char *i2c_hid_get_dmi_hid_report_desc_override(uint8_t *i2c_name,
+					       unsigned int *size);
+#else
+static inline struct i2c_hid_desc
+		   *i2c_hid_get_dmi_i2c_hid_desc_override(uint8_t *i2c_name)
+{ return NULL; }
+static inline char *i2c_hid_get_dmi_hid_report_desc_override(uint8_t *i2c_name,
+							     unsigned int *size)
+{ return NULL; }
+#endif
+
+#endif