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>

1 files changed, 16 insertions, 5 deletions

diff --git a/drivers/video/udlfb.c b/drivers/video/udlfb.c
index fecd2d3543bd..0b77af7bdf1b 100644
--- 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;
         }