HID: huion: Switch to generating report descriptor

Switch to generating tablet pen report descriptor from a template and
parameters retrieved from string descriptor 0x64.
Signed-off-by: NNikolai Kondrashov <spbnick@gmail.com>
Reviewed-by: NBenjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

drivers/hid/hid-huion.c

@@ -16,15 +16,29 @@
 #include <linux/hid.h>
 #include <linux/module.h>
 #include <linux/usb.h>
+#include <asm/unaligned.h>
 #include "usbhid/usbhid.h"
 
 #include "hid-ids.h"
 
-/* Original tablet report descriptor size */
-#define HUION_TABLET_RDESC_ORIG_SIZE	177
+/* Report descriptor template placeholder head */
+#define HUION_PH_HEAD	0xFE, 0xED, 0x1D
 
-/* Fixed tablet report descriptor */
-static __u8 huion_tablet_rdesc_fixed[] = {
+/* Report descriptor template placeholder IDs */
+enum huion_ph_id {
+	HUION_PH_ID_X_LM,
+	HUION_PH_ID_X_PM,
+	HUION_PH_ID_Y_LM,
+	HUION_PH_ID_Y_PM,
+	HUION_PH_ID_PRESSURE_LM,
+	HUION_PH_ID_NUM
+};
+
+/* Report descriptor template placeholder */
+#define HUION_PH(_ID) HUION_PH_HEAD, HUION_PH_ID_##_ID
+
+/* Fixed report descriptor template */
+static const __u8 huion_tablet_rdesc_template[] = {
 	0x05, 0x0D,             /*  Usage Page (Digitizer),                 */
 	0x09, 0x02,             /*  Usage (Pen),                            */
 	0xA1, 0x01,             /*  Collection (Application),               */
@@ -54,29 +68,37 @@ static __u8 huion_tablet_rdesc_fixed[] = {
 	0x55, 0xFD,             /*          Unit Exponent (-3),             */
 	0x34,                   /*          Physical Minimum (0),           */
 	0x09, 0x30,             /*          Usage (X),                      */
-	0x46, 0x40, 0x1F,   /*          Physical Maximum (8000),    */
-	0x26, 0x00, 0x7D,   /*          Logical Maximum (32000),    */
+	0x27, HUION_PH(X_LM),   /*          Logical Maximum (PLACEHOLDER),  */
+	0x47, HUION_PH(X_PM),   /*          Physical Maximum (PLACEHOLDER), */
 	0x81, 0x02,             /*          Input (Variable),               */
 	0x09, 0x31,             /*          Usage (Y),                      */
-	0x46, 0x88, 0x13,   /*          Physical Maximum (5000),    */
-	0x26, 0x20, 0x4E,   /*          Logical Maximum (20000),    */
+	0x27, HUION_PH(Y_LM),   /*          Logical Maximum (PLACEHOLDER),  */
+	0x47, HUION_PH(Y_PM),   /*          Physical Maximum (PLACEHOLDER), */
 	0x81, 0x02,             /*          Input (Variable),               */
 	0xB4,                   /*          Pop,                            */
 	0x09, 0x30,             /*          Usage (Tip Pressure),           */
-	0x26, 0xFF, 0x07,   /*          Logical Maximum (2047),     */
+	0x27,
+	HUION_PH(PRESSURE_LM),  /*          Logical Maximum (PLACEHOLDER),  */
 	0x81, 0x02,             /*          Input (Variable),               */
 	0xC0,                   /*      End Collection,                     */
 	0xC0                    /*  End Collection                          */
 };
 
+/* Driver data */
+struct huion_drvdata {
+	__u8 *rdesc;
+	unsigned int rsize;
+};
+
 static __u8 *huion_report_fixup(struct hid_device *hdev, __u8 *rdesc,
 		unsigned int *rsize)
 {
+	struct huion_drvdata *drvdata = hid_get_drvdata(hdev);
 	switch (hdev->product) {
 	case USB_DEVICE_ID_HUION_TABLET:
-		if (*rsize == HUION_TABLET_RDESC_ORIG_SIZE) {
-			rdesc = huion_tablet_rdesc_fixed;
-			*rsize = sizeof(huion_tablet_rdesc_fixed);
+		if (drvdata->rdesc != NULL) {
+			rdesc = drvdata->rdesc;
+			*rsize = drvdata->rsize;
 		}
 		break;
 	}
@@ -84,57 +106,124 @@ static __u8 *huion_report_fixup(struct hid_device *hdev, __u8 *rdesc,
 }
 
 /**
- * Enable fully-functional tablet mode by reading special string
- * descriptor.
+ * Enable fully-functional tablet mode and determine device parameters.
  *
  * @hdev:	HID device
- *
- * The specific string descriptor and data were discovered by sniffing
- * the Windows driver traffic.
  */
 static int huion_tablet_enable(struct hid_device *hdev)
 {
 	int rc;
-	char buf[22];
+	struct usb_device *usb_dev = hid_to_usb_dev(hdev);
+	struct huion_drvdata *drvdata = hid_get_drvdata(hdev);
+	u16 buf[6];
 
-	rc = usb_string(hid_to_usb_dev(hdev), 0x64, buf, sizeof(buf));
-	if (rc < 0)
-		return rc;
+	/*
+	 * Read string descriptor containing tablet parameters. The specific
+	 * string descriptor and data were discovered by sniffing the Windows
+	 * driver traffic.
+	 * NOTE: This enables fully-functional tablet mode.
+	 */
+	rc = usb_control_msg(usb_dev, usb_rcvctrlpipe(usb_dev, 0),
+				USB_REQ_GET_DESCRIPTOR, USB_DIR_IN,
+				(USB_DT_STRING << 8) + 0x64,
+				0x0409, buf, sizeof(buf),
+				USB_CTRL_GET_TIMEOUT);
+	if (rc == -EPIPE)
+		hid_warn(hdev, "device parameters not found\n");
+	else if (rc < 0)
+		hid_warn(hdev, "failed to get device parameters: %d\n", rc);
+	else if (rc != sizeof(buf))
+		hid_warn(hdev, "invalid device parameters\n");
+	else {
+		s32 params[HUION_PH_ID_NUM];
+		s32 resolution;
+		__u8 *p;
+		s32 v;
+
+		/* Extract device parameters */
+		params[HUION_PH_ID_X_LM] = le16_to_cpu(buf[1]);
+		params[HUION_PH_ID_Y_LM] = le16_to_cpu(buf[2]);
+		params[HUION_PH_ID_PRESSURE_LM] = le16_to_cpu(buf[4]);
+		resolution = le16_to_cpu(buf[5]);
+		if (resolution == 0) {
+			params[HUION_PH_ID_X_PM] = 0;
+			params[HUION_PH_ID_Y_PM] = 0;
+		} else {
+			params[HUION_PH_ID_X_PM] = params[HUION_PH_ID_X_LM] *
+							1000 / resolution;
+			params[HUION_PH_ID_Y_PM] = params[HUION_PH_ID_Y_LM] *
+							1000 / resolution;
+		}
+
+		/* Allocate fixed report descriptor */
+		drvdata->rdesc = devm_kmalloc(&hdev->dev,
+					sizeof(huion_tablet_rdesc_template),
+					GFP_KERNEL);
+		if (drvdata->rdesc == NULL) {
+			hid_err(hdev, "failed to allocate fixed rdesc\n");
+			return -ENOMEM;
+		}
+		drvdata->rsize = sizeof(huion_tablet_rdesc_template);
+
+		/* Format fixed report descriptor */
+		memcpy(drvdata->rdesc, huion_tablet_rdesc_template,
+			drvdata->rsize);
+		for (p = drvdata->rdesc;
+		     p <= drvdata->rdesc + drvdata->rsize - 4;) {
+			if (p[0] == 0xFE && p[1] == 0xED && p[2] == 0x1D &&
+			    p[3] < sizeof(params)) {
+				v = params[p[3]];
+				put_unaligned(cpu_to_le32(v), (s32 *)p);
+				p += 4;
+			} else {
+				p++;
+			}
+		}
+	}
 
 	return 0;
 }
 
 static int huion_probe(struct hid_device *hdev, const struct hid_device_id *id)
 {
-	int ret;
-
-	ret = hid_parse(hdev);
-	if (ret) {
-		hid_err(hdev, "parse failed\n");
-		goto err;
-	}
+	int rc;
+	struct usb_interface *intf = to_usb_interface(hdev->dev.parent);
+	struct huion_drvdata *drvdata;
 
-	ret = hid_hw_start(hdev, HID_CONNECT_DEFAULT);
-	if (ret) {
-		hid_err(hdev, "hw start failed\n");
-		goto err;
+	/* Allocate and assign driver data */
+	drvdata = devm_kzalloc(&hdev->dev, sizeof(*drvdata), GFP_KERNEL);
+	if (drvdata == NULL) {
+		hid_err(hdev, "failed to allocate driver data\n");
+		return -ENOMEM;
 	}
+	hid_set_drvdata(hdev, drvdata);
 
 	switch (id->product) {
 	case USB_DEVICE_ID_HUION_TABLET:
-		ret = huion_tablet_enable(hdev);
-		if (ret) {
+		/* If this is the pen interface */
+		if (intf->cur_altsetting->desc.bInterfaceNumber == 0) {
+			rc = huion_tablet_enable(hdev);
+			if (rc) {
 				hid_err(hdev, "tablet enabling failed\n");
-			goto enabling_err;
+				return rc;
+			}
 		}
 		break;
 	}
 
+	rc = hid_parse(hdev);
+	if (rc) {
+		hid_err(hdev, "parse failed\n");
+		return rc;
+	}
+
+	rc = hid_hw_start(hdev, HID_CONNECT_DEFAULT);
+	if (rc) {
+		hid_err(hdev, "hw start failed\n");
+		return rc;
+	}
+
 	return 0;
-enabling_err:
-	hid_hw_stop(hdev);
-err:
-	return ret;
 }
 
 static int huion_raw_event(struct hid_device *hdev, struct hid_report *report,