[Linux-parport] [PATCH 7/7] usb: misc: uss720: check for incompatible versions of the Belkin F5U002

[Alex Henrie]

The incompatible device in my possession has a sticker that says
"F5U002 Rev 2" and "P80453-B", and lsusb identifies it as
"050d:0002 Belkin Components IEEE-1284 Controller". There is a bug
report from 2007 from Michael Trausch who was seeing the exact same
errors that I saw in 2024 trying to use this cable.

Link: https://lore.kernel.org/all/46DE5830.9060401@trausch.us/
Signed-off-by: Alex Henrie <alexhenrie24 at gmail.com>
---
 drivers/usb/misc/uss720.c | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/drivers/usb/misc/uss720.c b/drivers/usb/misc/uss720.c
index 5803919d7cc4..0ad2bfc6af78 100644
--- a/drivers/usb/misc/uss720.c
+++ b/drivers/usb/misc/uss720.c
@@ -677,7 +677,7 @@ static int uss720_probe(struct usb_interface *intf,
 	struct parport_uss720_private *priv;
 	struct parport *pp;
 	unsigned char reg;
-	int i;
+	int ret;
 
 	dev_dbg(&intf->dev, "probe: vendor id 0x%x, device id 0x%x\n",
 		le16_to_cpu(usbdev->descriptor.idVendor),
@@ -688,8 +688,8 @@ static int uss720_probe(struct usb_interface *intf,
 		usb_put_dev(usbdev);
 		return -ENODEV;
 	}
-	i = usb_set_interface(usbdev, intf->altsetting->desc.bInterfaceNumber, 2);
-	dev_dbg(&intf->dev, "set interface result %d\n", i);
+	ret = usb_set_interface(usbdev, intf->altsetting->desc.bInterfaceNumber, 2);
+	dev_dbg(&intf->dev, "set interface result %d\n", ret);
 
 	interface = intf->cur_altsetting;
 
@@ -728,12 +728,18 @@ static int uss720_probe(struct usb_interface *intf,
 	set_1284_register(pp, 7, 0x00, GFP_KERNEL);
 	set_1284_register(pp, 6, 0x30, GFP_KERNEL);  /* PS/2 mode */
 	set_1284_register(pp, 2, 0x0c, GFP_KERNEL);
-	/* debugging */
-	get_1284_register(pp, 0, &reg, GFP_KERNEL);
+
+	/* The Belkin F5U002 Rev 2 P80453-B USB parallel port adapter shares the
+	 * device ID 050d:0002 with some other device that works with this
+	 * driver, but it itself does not. Detect and handle the bad cable
+	 * here. */
+	ret = get_1284_register(pp, 0, &reg, GFP_KERNEL);
 	dev_dbg(&intf->dev, "reg: %7ph\n", priv->reg);
+	if (ret < 0)
+		return ret;
 
-	i = usb_find_last_int_in_endpoint(interface, &epd);
-	if (!i) {
+	ret = usb_find_last_int_in_endpoint(interface, &epd);
+	if (!ret) {
 		dev_dbg(&intf->dev, "epaddr %d interval %d\n",
 				epd->bEndpointAddress, epd->bInterval);
 	}
-- 
2.44.0