V4L/DVB (6238): bw-qcam: use data_reverse instead of manually poking the control register

Fixes use of parport_write_control() to match the newer interface that
requires explicit parport_data_reverse() and parport_data_forward() calls.
This eliminates the following error message and restores the original
intended behavior:

parport0 (bw-qcam): use data_reverse for this!

Also increases threshold in qc_detect() from 300 to 400, as my camera often
results in a count of approx 330.  Added a kernel error message to indicate
detection failure.

Thanks Ray and Randy for your comments, and for pointing out that I
needed to reset the port to forward mode!
Signed-off-by: NBrett T. Warden <brett.warden@gmail.com>
Acked-by: NAlan Cox <alan@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NMauro Carvalho Chehab <mchehab@infradead.org>

drivers/media/video/bw-qcam.c

@@ -104,6 +104,17 @@ static inline void write_lpdata(struct qcam_device *q, int d)
 
 static inline void write_lpcontrol(struct qcam_device *q, int d)
 {
+	if(0x20 & d) {
+		/* Set bidirectional mode to reverse (data in) */
+		parport_data_reverse(q->pport);
+	} else {
+		/* Set bidirectional mode to forward (data out) */
+		parport_data_forward(q->pport);
+	}
+
+	/* Now issue the regular port command, but strip out the
+	 * direction flag */
+	d &= ~0x20;
 	parport_write_control(q->pport, d);
 }
 
@@ -344,10 +355,13 @@ static int qc_detect(struct qcam_device *q)
 	/* Be (even more) liberal in what you accept...  */
 
 /*	if (count > 30 && count < 200) */
-	if (count > 20 && count < 300)
+	if (count > 20 && count < 400)
+	{
 		return 1;	/* found */
-	else
+	} else {
+		printk(KERN_ERR "No Quickcam found on port %s\n", q->pport->name);
 		return 0;	/* not found */
+	}
 }