HID: elo: add quirks for broken firmware

One firmare version in the devices the driver takes care of is
completely broken and needs periodic pokes from our side. We
implemented this as a periodic delayed queue. The idea of the pokes
was taken from the suse enterprise kernel, in particular from Libor's
"Elo touchscreen firmware M workaround".

I am quoting him here:
This patch adds periodic polling of the Elo USB touchscreens. Needed
as a workaround for devices with M-level firmware, otherwise these
devices are known to misbehave (as reported by Elo developers).

Signed-off-by: Jiri Slaby <[e-mail]>
Tested-by: Petr Ostadal <[e-mail]>
Cc: Oliver Neukum <[e-mail]>
Cc: Vojtech Pavlik <[e-mail]>
Cc: Egbert Eich <[e-mail]>
Cc: Libor Pechacek <[e-mail]>
Signed-off-by: Jiri Kosina <[e-mail]>

drivers/hid/hid-elo.c

···
 #include <linux/hid.h>
 #include <linux/input.h>
 #include <linux/module.h>
+#include <linux/usb.h>
+#include <linux/workqueue.h>
 
 #include "hid-ids.h"
+
+#define ELO_PERIODIC_READ_INTERVAL	HZ
+#define ELO_SMARTSET_CMD_TIMEOUT	2000 /* msec */
+
+/* Elo SmartSet commands */
+#define ELO_FLUSH_SMARTSET_RESPONSES	0x02 /* Flush all pending smartset responses */
+#define ELO_SEND_SMARTSET_COMMAND	0x05 /* Send a smartset command */
+#define ELO_GET_SMARTSET_RESPONSE	0x06 /* Get a smartset response */
+#define ELO_DIAG			0x64 /* Diagnostics command */
+#define ELO_SMARTSET_PACKET_SIZE	8
+
+struct elo_priv {
+	struct usb_device *usbdev;
+	struct delayed_work work;
+	unsigned char buffer[ELO_SMARTSET_PACKET_SIZE];
+};
+
+static struct workqueue_struct *wq;
+static bool use_fw_quirk = true;
+module_param(use_fw_quirk, bool, S_IRUGO);
+MODULE_PARM_DESC(use_fw_quirk, "Do periodic pokes for broken M firmwares (default = true)");
 
 static void elo_input_configured(struct hid_device *hdev,
 		struct hid_input *hidinput)
···
 	return 0;
 }
 
+static int elo_smartset_send_get(struct usb_device *dev, u8 command,
+		void *data)
+{
+	unsigned int pipe;
+	u8 dir;
+
+	if (command == ELO_SEND_SMARTSET_COMMAND) {
+		pipe = usb_sndctrlpipe(dev, 0);
+		dir = USB_DIR_OUT;
+	} else if (command == ELO_GET_SMARTSET_RESPONSE) {
+		pipe = usb_rcvctrlpipe(dev, 0);
+		dir = USB_DIR_IN;
+	} else
+		return -EINVAL;
+
+	return usb_control_msg(dev, pipe, command,
+			dir | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
+			0, 0, data, ELO_SMARTSET_PACKET_SIZE,
+			ELO_SMARTSET_CMD_TIMEOUT);
+}
+
+static int elo_flush_smartset_responses(struct usb_device *dev)
+{
+	return usb_control_msg(dev, usb_sndctrlpipe(dev, 0),
+			ELO_FLUSH_SMARTSET_RESPONSES,
+			USB_DIR_OUT | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
+			0, 0, NULL, 0, USB_CTRL_SET_TIMEOUT);
+}
+
+static void elo_work(struct work_struct *work)
+{
+	struct elo_priv *priv = container_of(work, struct elo_priv, work.work);
+	struct usb_device *dev = priv->usbdev;
+	unsigned char *buffer = priv->buffer;
+	int ret;
+
+	ret = elo_flush_smartset_responses(dev);
+	if (ret < 0) {
+		dev_err(&dev->dev, "initial FLUSH_SMARTSET_RESPONSES failed, error %d\n",
+				ret);
+		goto fail;
+	}
+
+	/* send Diagnostics command */
+	*buffer = ELO_DIAG;
+	ret = elo_smartset_send_get(dev, ELO_SEND_SMARTSET_COMMAND, buffer);
+	if (ret < 0) {
+		dev_err(&dev->dev, "send Diagnostics Command failed, error %d\n",
+				ret);
+		goto fail;
+	}
+
+	/* get the result */
+	ret = elo_smartset_send_get(dev, ELO_GET_SMARTSET_RESPONSE, buffer);
+	if (ret < 0) {
+		dev_err(&dev->dev, "get Diagnostics Command response failed, error %d\n",
+				ret);
+		goto fail;
+	}
+
+	/* read the ack */
+	if (*buffer != 'A') {
+		ret = elo_smartset_send_get(dev, ELO_GET_SMARTSET_RESPONSE,
+				buffer);
+		if (ret < 0) {
+			dev_err(&dev->dev, "get acknowledge response failed, error %d\n",
+					ret);
+			goto fail;
+		}
+	}
+
+fail:
+	ret = elo_flush_smartset_responses(dev);
+	if (ret < 0)
+		dev_err(&dev->dev, "final FLUSH_SMARTSET_RESPONSES failed, error %d\n",
+				ret);
+	queue_delayed_work(wq, &priv->work, ELO_PERIODIC_READ_INTERVAL);
+}
+
+/*
+ * Not all Elo devices need the periodic HID descriptor reads.
+ * Only firmware version M needs this.
+ */
+static bool elo_broken_firmware(struct usb_device *dev)
+{
+	return use_fw_quirk && le16_to_cpu(dev->descriptor.bcdDevice) == 0x10d;
+}
+
 static int elo_probe(struct hid_device *hdev, const struct hid_device_id *id)
 {
+	struct elo_priv *priv;
 	int ret;
+
+	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	INIT_DELAYED_WORK(&priv->work, elo_work);
+	priv->usbdev = interface_to_usbdev(to_usb_interface(hdev->dev.parent));
+
+	hid_set_drvdata(hdev, priv);
 
 	ret = hid_parse(hdev);
 	if (ret) {
···
 		goto err_free;
 	}
 
+	if (elo_broken_firmware(priv->usbdev)) {
+		hid_info(hdev, "broken firmware found, installing workaround\n");
+		queue_delayed_work(wq, &priv->work, ELO_PERIODIC_READ_INTERVAL);
+	}
+
 	return 0;
 err_free:
+	kfree(priv);
 	return ret;
 }
 
 static void elo_remove(struct hid_device *hdev)
 {
+	struct elo_priv *priv = hid_get_drvdata(hdev);
+
 	hid_hw_stop(hdev);
+	flush_workqueue(wq);
+	kfree(priv);
 }
 
 static const struct hid_device_id elo_devices[] = {
···
 
 static int __init elo_driver_init(void)
 {
-	return hid_register_driver(&elo_driver);
+	int ret;
+
+	wq = create_singlethread_workqueue("elousb");
+	if (!wq)
+		return -ENOMEM;
+
+	ret = hid_register_driver(&elo_driver);
+	if (ret)
+		destroy_workqueue(wq);
+
+	return ret;
 }
 module_init(elo_driver_init);
 
 static void __exit elo_driver_exit(void)
 {
 	hid_unregister_driver(&elo_driver);
+	destroy_workqueue(wq);
 }
 module_exit(elo_driver_exit);