Add V4L2_FIELD_ALTERNATE support to SAA7134

[Chris Byrne <chris.byrne (at) monstavision.com>]

Hartmut Hackmann wrote:
> Hi, Chris
>
> I finally found the time to investigate your patch closely.
> I agree to your change in saa7134-video.c, but i am in doubt
> concerning the task conditions in saa7134-core.c

From experimentation I know that without that change, the corrected 
conditions in saa7134_irq_video_done are not met. Admittedly I haven't 
gone through the saa driver in detail to work out why they need to be 
swapped. From a brief investigation the in/out fields are not inverted 
(i.e. D5^D4 = 0 in SAA7134_SCALER_STATUS1). So perhaps further confusion 
over what an odd/upper/top field is?

An alternative to my patch is to instead get saa7134_irq_video_done to 
correct the field type. Changing from the requested field type to the 
actual:

dev->video_q.curr->vb.field = (status & 0x10)
        ? V4L2_FIELD_TOP : V4L2_FIELD_BOTTOM;

I actually prefer this method as you don't need to wait for a field of 
the correct type.

> Do you try to capture in overlay mode?

No, my app only uses mmap access. All other apps I've tried (tvtime, 
mplayer) appear to fall in the V4L2_FIELD_HAS_BOTH category. Then again 
they don't seem to support overlay mode either.

> This might be right for your application. But if i understand things
> right, you patch swaps the task assignment in field mode. In other
> words: in capture mode now the field assignment is wrong. Before we
> try to find a solution, can you confirm this?

Not really. For starters it doesn't help that you can't specify 
V4L2_FIELD_ALTERNATE in overlay mode. Following the bttv-driver.c 
convention verify_preview returns -EINVAL for V4L2_FIELD_ALTERNATE.

Since my patch only affects field modes that leaves testing for 
V4L2_FIELD_TOP and/or V4L2_FIELD_BOTTOM. Unfortunately I don't have a 
source which will spit out a different colour for each field... which 
come to think of it would be really handy.

Thanks,
 Chris

diff -up /home/chris/vanilla_video/saa7134/saa7134-video.c linux/drivers/media/video/saa7134/saa7134-video.c
--- /home/chris/vanilla_video/saa7134/saa7134-video.c	2006-03-28 18:49:02.000000000 +1200
+++ linux/drivers/media/video/saa7134/saa7134-video.c	2006-05-22 15:24:59.000000000 +1200
 (at)  (at)  -1501,6 +1501,7  (at)  (at)  static int saa7134_try_fmt(struct saa713
 		switch (field) {
 		case V4L2_FIELD_TOP:
 		case V4L2_FIELD_BOTTOM:
+		case V4L2_FIELD_ALTERNATE:
 			maxh = maxh / 2;
 			break;
 		case V4L2_FIELD_INTERLACED:
 (at)  (at)  -2430,12 +2431,9  (at)  (at)  void saa7134_irq_video_done(struct saa71
 			}
 			if (!dev->video_q.curr->top_seen)
 				goto done;
-		} else if (field == V4L2_FIELD_TOP) {
-			if ((status & 0x10) != 0x10)
-				goto done;
-		} else if (field == V4L2_FIELD_BOTTOM) {
-			if ((status & 0x10) != 0x00)
-				goto done;
+		} else {
+			dev->video_q.curr->vb.field = (status & 0x10) 
+				? V4L2_FIELD_TOP : V4L2_FIELD_BOTTOM;
 		}
 		dev->video_q.curr->vb.field_count = dev->video_fieldcount;
 		saa7134_buffer_finish(dev,&dev->video_q,STATE_DONE);

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