udlfb: Search config descriptor if not at device level

For at least one DisplayLink device, the vendor-specific information can
be found in the config descriptor instead of as a separate, device-level
descriptor.  This patch searches the current interface (of the current
config descriptor) for the DL vendor-specific descriptor.

Signed-off-by: Andrew Kephart <akephart@akephart.org>
Signed-off-by: Bernie Thompson <bernie@plugable.com>
Signed-off-by: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>

diff --git a/drivers/video/udlfb.c b/drivers/video/udlfb.c
index fecd2d3..0b77af7 100644 (file)
--- a/drivers/video/udlfb.c
+++ b/drivers/video/udlfb.c
@@ -1479,21 +1479,30 @@ static int dlfb_select_std_channel(struct dlfb_data *dev)
 }
 
 static int dlfb_parse_vendor_descriptor(struct dlfb_data *dev,
-                                       struct usb_device *usbdev)
+                                       struct usb_interface *interface)
 {
        char *desc;
        char *buf;
        char *desc_end;
 
-       u8 total_len = 0;
+       int total_len = 0;
 
        buf = kzalloc(MAX_VENDOR_DESCRIPTOR_SIZE, GFP_KERNEL);
        if (!buf)
                return false;
        desc = buf;
 
-       total_len = usb_get_descriptor(usbdev, 0x5f, /* vendor specific */
-                                   0, desc, MAX_VENDOR_DESCRIPTOR_SIZE);
+       total_len = usb_get_descriptor(interface_to_usbdev(interface),
+                                       0x5f, /* vendor specific */
+                                       0, desc, MAX_VENDOR_DESCRIPTOR_SIZE);
+
+       /* if not found, look in configuration descriptor */
+       if (total_len < 0) {
+               if (0 == usb_get_extra_descriptor(interface->cur_altsetting,
+                       0x5f, &desc))
+                       total_len = (int) desc[0];
+       }
+
        if (total_len > 5) {
                pr_info("vendor descriptor length:%x data:%02x %02x %02x %02x" \
                        "%02x %02x %02x %02x %02x %02x %02x\n",
@@ -1534,6 +1543,8 @@ static int dlfb_parse_vendor_descriptor(struct dlfb_data *dev,
                        }
                        desc += length;
                }
+       } else {
+               pr_info("vendor descriptor not available (%d)\n", total_len);
        }
 
        goto success;
@@ -1583,7 +1594,7 @@ static int dlfb_usb_probe(struct usb_interface *interface,
 
        dev->sku_pixel_limit = 2048 * 1152; /* default to maximum */
 
-       if (!dlfb_parse_vendor_descriptor(dev, usbdev)) {
+       if (!dlfb_parse_vendor_descriptor(dev, interface)) {
                pr_err("firmware not recognized. Assume incompatible device\n");
                goto error;
        }