sd_desc->stop0 and sd_desc->stopN hooks are meant to access
the device hardware, stopping the transfer. Thus, hardware
presence should be checked before calling them.

This means that sd_desc.start is not allowed to allocate resources,
since sd_desc.stop0 and sd_desc.stopN won't be releasing when
the USB device is disconnected.

TODO: Check what's the deal with the konica device, which is allocating
URB memory in sd_desc.start. This seems wrong.

Signed-off-by: Ezequiel Garcia <ezequ...@collabora.com>
---
 drivers/media/usb/gspca/gspca.c | 11 ++++++-----
 drivers/media/usb/gspca/gspca.h |  6 +++---
 2 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/drivers/media/usb/gspca/gspca.c b/drivers/media/usb/gspca/gspca.c
index 4d7517411cc2..98b68a7a52c0 100644
--- a/drivers/media/usb/gspca/gspca.c
+++ b/drivers/media/usb/gspca/gspca.c
@@ -745,15 +745,16 @@ static void gspca_stream_off(struct gspca_dev *gspca_dev)
 {
        gspca_dev->streaming = false;
        gspca_dev->usb_err = 0;
-       if (gspca_dev->sd_desc->stopN)
+       if (gspca_dev->present && gspca_dev->sd_desc->stopN)
                gspca_dev->sd_desc->stopN(gspca_dev);
        destroy_urbs(gspca_dev);
        gspca_input_destroy_urb(gspca_dev);
-       gspca_set_alt0(gspca_dev);
-       if (gspca_dev->present)
+       if (gspca_dev->present) {
+               gspca_set_alt0(gspca_dev);
                gspca_input_create_urb(gspca_dev);
-       if (gspca_dev->sd_desc->stop0)
-               gspca_dev->sd_desc->stop0(gspca_dev);
+               if (gspca_dev->sd_desc->stop0)
+                       gspca_dev->sd_desc->stop0(gspca_dev);
+       }
        gspca_dbg(gspca_dev, D_STREAM, "stream off OK\n");
 }
 
diff --git a/drivers/media/usb/gspca/gspca.h b/drivers/media/usb/gspca/gspca.h
index b0ced2e14006..e0ca120d2e31 100644
--- a/drivers/media/usb/gspca/gspca.h
+++ b/drivers/media/usb/gspca/gspca.h
@@ -105,13 +105,13 @@ struct sd_desc {
        cam_cf_op config;       /* called on probe */
        cam_op init;            /* called on probe and resume */
        cam_op init_controls;   /* called on probe */
-       cam_op start;           /* called on stream on after URBs creation */
+       cam_op start;           /* called on stream on after URBs creation. 
Can't allocate any resources here! */
        cam_pkt_op pkt_scan;
 /* optional operations */
        cam_op isoc_init;       /* called on stream on before getting the EP */
        cam_op isoc_nego;       /* called when URB submit failed with NOSPC */
-       cam_v_op stopN;         /* called on stream off - main alt */
-       cam_v_op stop0;         /* called on stream off & disconnect - alt 0 */
+       cam_v_op stopN;         /* called on stream off, only if usb device is 
present - main alt */
+       cam_v_op stop0;         /* called on stream off, only if usb device is 
present - alt 0 */
        cam_v_op dq_callback;   /* called when a frame has been dequeued */
        cam_get_jpg_op get_jcomp;
        cam_set_jpg_op set_jcomp;
-- 
2.20.1

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