On Mon, 2016-05-23 at 13:39 +0200, Martin Kepplinger wrote:

It's *really* fun to use as an input tablet though! So let's support this
for everybody.

Hi,

I am afraid there are a few issues.

1. Why the kernel thread?
2. This driver has questionable power management.

	Regards
		Oliver

+static int pegasus_probe(struct usb_interface *intf,
+			 const struct usb_device_id *id)
+{
+	struct usb_device *dev = interface_to_usbdev(intf);
+	struct usb_endpoint_descriptor *endpoint;
+	struct pegasus *pegasus;
+	struct input_dev *input_dev;
+	int error;
+	int pipe, maxp;
+
+	/* we control interface 0 */
+	if (intf->cur_altsetting->desc.bInterfaceNumber == 1)
+		return -ENODEV;
+
+	endpoint = &intf->cur_altsetting->endpoint[0].desc;
+
+	pegasus = kzalloc(sizeof(*pegasus), GFP_KERNEL);
+	input_dev = input_allocate_device();
+	if (!pegasus || !input_dev) {
+		error = -ENOMEM;
+		goto err_free_mem;
+	}
+
+	pegasus->usbdev = dev;
+	pegasus->dev = input_dev;
+
+	pegasus->data = usb_alloc_coherent(dev, endpoint->wMaxPacketSize,
+					   GFP_KERNEL, &pegasus->data_dma);
+	if (!pegasus->data) {
+		error = -ENOMEM;
+		goto err_free_mem;
+	}
+
+	pegasus->irq = usb_alloc_urb(0, GFP_KERNEL);
+	if (!pegasus->irq) {
+		error = -ENOMEM;
+		goto err_free_mem;
+	}
+
+	pipe = usb_rcvintpipe(dev, endpoint->bEndpointAddress);
+	maxp = usb_maxpacket(dev, pipe, usb_pipeout(pipe));
+	pegasus->data_len = maxp;
+
+	usb_fill_int_urb(pegasus->irq, dev, pipe, pegasus->data, maxp,
+			 pegasus_irq, pegasus, endpoint->bInterval);
+
+	pegasus->irq->transfer_dma = pegasus->data_dma;
+	pegasus->irq->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;
+
+	if (dev->manufacturer)
+		strlcpy(pegasus->name, dev->manufacturer,
+			sizeof(pegasus->name));
+
+	if (dev->product) {
+		if (dev->manufacturer)
+			strlcat(pegasus->name, " ", sizeof(pegasus->name));
+		strlcat(pegasus->name, dev->product, sizeof(pegasus->name));
+	}
+
+	if (!strlen(pegasus->name))
+		snprintf(pegasus->name, sizeof(pegasus->name),
+			 "USB Pegasus Device %04x:%04x",
+			 le16_to_cpu(dev->descriptor.idVendor),
+			 le16_to_cpu(dev->descriptor.idProduct));
+
+	usb_make_path(dev, pegasus->phys, sizeof(pegasus->phys));
+	strlcat(pegasus->phys, "/input0", sizeof(pegasus->phys));
+
+	usb_set_intfdata(intf, pegasus);
+
+	input_dev->name = pegasus->name;
+	input_dev->phys = pegasus->phys;
+	usb_to_input_id(dev, &input_dev->id);
+	input_dev->dev.parent = &intf->dev;
+
+	input_set_drvdata(input_dev, pegasus);
+
+	input_dev->open = pegasus_open;
+	input_dev->close = pegasus_close;
+
+	__set_bit(EV_ABS, input_dev->evbit);
+	__set_bit(EV_KEY, input_dev->evbit);
+
+	__set_bit(ABS_X, input_dev->absbit);
+	__set_bit(ABS_Y, input_dev->absbit);
+
+	__set_bit(BTN_TOUCH, input_dev->keybit);
+	__set_bit(BTN_RIGHT, input_dev->keybit);
+	__set_bit(BTN_TOOL_PEN, input_dev->keybit);
+
+	__set_bit(INPUT_PROP_DIRECT, input_dev->propbit);
+	__set_bit(INPUT_PROP_POINTER, input_dev->propbit);
+
+	input_set_abs_params(input_dev, ABS_X, -1500, 1500, 8, 0);
+	input_set_abs_params(input_dev, ABS_Y, 1600, 3000, 8, 0);
+
+	error = input_register_device(pegasus->dev);
+	if (error)
+		goto err_free_dma;
+
+	pegasus_thread = kthread_run(pegasus_threadf, pegasus,
+				     "pegasus_notetaker_thread");

Why is that needed?

+	if (IS_ERR(pegasus_thread)) {
+		error = -ENOMEM;
+		goto err_free_dma;
+	}
+
+	return 0;
+
+err_free_dma:
+	usb_free_coherent(dev, pegasus->data_len,
+			  pegasus->data, pegasus->data_dma);
+
+	usb_free_urb(pegasus->irq);
+err_free_mem:
+	kfree(pegasus);
+	usb_set_intfdata(intf, NULL);
+
+	return error;
+}
+
+static void pegasus_disconnect(struct usb_interface *intf)
+{
+	struct pegasus *pegasus = usb_get_intfdata(intf);
+
+	input_unregister_device(pegasus->dev);
+	if (pegasus_thread) {
+		if (kthread_stop(pegasus_thread) == -EINTR)
+			dev_err(&pegasus->usbdev->dev,
+				"wake_up_proc was never called\n");
+	}
+
+	usb_free_urb(pegasus->irq);
+	usb_free_coherent(interface_to_usbdev(intf),
+			  pegasus->data_len, pegasus->data,
+			  pegasus->data_dma);
+	kfree(pegasus);
+	usb_set_intfdata(intf, NULL);
+}
+
+static const struct usb_device_id pegasus_ids[] = {
+	{ USB_DEVICE(USB_VENDOR_ID_PEGASUSTECH,
+		     USB_DEVICE_ID_PEGASUS_NOTETAKER_EN100) },
+	{ }
+};
+MODULE_DEVICE_TABLE(usb, pegasus_ids);
+
+static struct usb_driver pegasus_driver = {
+	.name		= "pegasus_notetaker",
+	.probe		= pegasus_probe,
+	.disconnect	= pegasus_disconnect,
+	.id_table	= pegasus_ids,
+};
+
+module_usb_driver(pegasus_driver);
+
+MODULE_AUTHOR("Martin Kepplinger [off-list ref]");
+MODULE_DESCRIPTION("Pegasus Mobile Notetaker Pen tablet driver");
+MODULE_LICENSE("GPL");