[media] em28xx: ignore isoc DVB USB endpoints with wMaxPacketSize = 0 bytes for all alt settings

Some devices without DVB support (such as the "Terratec Grabby" and
"Easycap DC-60") provide isochronous DVB USB endpoints with wMaxPacketSize set
to 0 bytes for all alt settings.
Ignore these endpoints and avoid registering a DVB device node and loading the
DVB driver extension.

Signed-off-by: Frank Schäfer <fschaefer.oss@googlemail.com>
Tested-by: Timo Teräs <timo.teras@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

1 files changed, 8 insertions, 1 deletions

diff --git a/drivers/media/usb/em28xx/em28xx-cards.c b/drivers/media/usb/em28xx/em28xx-cards.c
index 54e0362d8e3d..096206334134 100644
--- a/drivers/media/usb/em28xx/em28xx-cards.c
+++ b/drivers/media/usb/em28xx/em28xx-cards.c
@@ -3357,14 +3357,15 @@ static int em28xx_usb_probe(struct usb_interface *interface,
                                                 dev->analog_ep_bulk =
                                                             e->bEndpointAddress;
                                         } else {
-                                                has_dvb = true;
                                                 if (usb_endpoint_xfer_isoc(e)) {
                                                         dev->dvb_ep_isoc = e->bEndpointAddress;
                                                         if (size > dev->dvb_max_pkt_size_isoc) {
+                                                                has_dvb = true; /* see NOTE (~) */
                                                                 dev->dvb_max_pkt_size_isoc = size;
                                                                 dev->dvb_alt_isoc = i;
                                                         }
                                                 } else {
+                                                        has_dvb = true;
                                                         dev->dvb_ep_bulk = e->bEndpointAddress;
                                                 }
                                         }
@@ -3391,6 +3392,12 @@ static int em28xx_usb_probe(struct usb_interface *interface,
                          * so far. But there might be devices for which this
                          * logic is not sufficient...
                          */
+                        /*
+                         * NOTE (~): some manufacturers (e.g. Terratec) disable
+                         * endpoints by setting wMaxPacketSize to 0 bytes for
+                         * all alt settings. So far, we've seen this for
+                         * DVB isoc endpoints only.
+                         */
                 }
         }