[media] em28xx: fix+improve the register (usb control message) debugging

- avoid duplicate debugging messages in em28xx_read_reg_req_len()
- do not describe successful usb transfers in em28xx_read_reg_len()
  as "failed"
- report errors in em28xx_write_regs_req(), too
- print the usb error numbers, too

Signed-off-by: Frank Schäfer <fschaefer.oss@googlemail.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

drivers/media/usb/em28xx/em28xx-core.c

@@ -91,22 +91,16 @@ int em28xx_read_reg_req_len(struct em28xx *dev, u8 req, u16 reg,
 	if (len > URB_MAX_CTRL_SIZE)
 		return -EINVAL;
 
-	em28xx_regdbg("(pipe 0x%08x): IN:  %02x %02x %02x %02x %02x %02x %02x %02x ",
-		     pipe, USB_DIR_IN | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
-		     req, 0, 0,
-		     reg & 0xff, reg >> 8,
-		     len & 0xff, len >> 8);
-
 	mutex_lock(&dev->ctrl_urb_lock);
 	ret = usb_control_msg(udev, pipe, req,
 			      USB_DIR_IN | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
 			      0x0000, reg, dev->urb_buf, len, HZ);
 	if (ret < 0) {
-		em28xx_regdbg("(pipe 0x%08x): IN:  %02x %02x %02x %02x %02x %02x %02x %02x  failed\n",
+		em28xx_regdbg("(pipe 0x%08x): IN:  %02x %02x %02x %02x %02x %02x %02x %02x  failed with error %i\n",
 			     pipe, USB_DIR_IN | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
 			     req, 0, 0,
 			     reg & 0xff, reg >> 8,
-			     len & 0xff, len >> 8);
+			     len & 0xff, len >> 8, ret);
 		mutex_unlock(&dev->ctrl_urb_lock);
 		return usb_translate_errors(ret);
 	}
@@ -116,7 +110,7 @@ int em28xx_read_reg_req_len(struct em28xx *dev, u8 req, u16 reg,
 
 	mutex_unlock(&dev->ctrl_urb_lock);
 
-	em28xx_regdbg("(pipe 0x%08x): IN:  %02x %02x %02x %02x %02x %02x %02x %02x  failed <<< %*ph\n",
+	em28xx_regdbg("(pipe 0x%08x): IN:  %02x %02x %02x %02x %02x %02x %02x %02x <<< %*ph\n",
 		     pipe, USB_DIR_IN | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
 		     req, 0, 0,
 		     reg & 0xff, reg >> 8,
@@ -164,13 +158,6 @@ int em28xx_write_regs_req(struct em28xx *dev, u8 req, u16 reg, char *buf,
 	if ((len < 1) || (len > URB_MAX_CTRL_SIZE))
 		return -EINVAL;
 
-	em28xx_regdbg("(pipe 0x%08x): OUT: %02x %02x %02x %02x %02x %02x %02x %02x >>> %*ph\n",
-		      pipe,
-		      USB_DIR_OUT | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
-		      req, 0, 0,
-		      reg & 0xff, reg >> 8,
-		      len & 0xff, len >> 8, len, buf);
-
 	mutex_lock(&dev->ctrl_urb_lock);
 	memcpy(dev->urb_buf, buf, len);
 	ret = usb_control_msg(udev, pipe, req,
@@ -178,8 +165,22 @@ int em28xx_write_regs_req(struct em28xx *dev, u8 req, u16 reg, char *buf,
 			      0x0000, reg, dev->urb_buf, len, HZ);
 	mutex_unlock(&dev->ctrl_urb_lock);
 
-	if (ret < 0)
+	if (ret < 0) {
+		em28xx_regdbg("(pipe 0x%08x): OUT:  %02x %02x %02x %02x %02x %02x %02x %02x >>> %*ph  failed with error %i\n",
+			      pipe,
+			      USB_DIR_OUT | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
+			      req, 0, 0,
+			      reg & 0xff, reg >> 8,
+			      len & 0xff, len >> 8, len, buf, ret);
 		return usb_translate_errors(ret);
+	}
+
+	em28xx_regdbg("(pipe 0x%08x): OUT:  %02x %02x %02x %02x %02x %02x %02x %02x >>> %*ph\n",
+		      pipe,
+		      USB_DIR_OUT | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
+		      req, 0, 0,
+		      reg & 0xff, reg >> 8,
+		      len & 0xff, len >> 8, len, buf);
 
 	if (dev->wait_after_write)
 		msleep(dev->wait_after_write);