V4L/DVB (5034): Pvrusb2: Enable radio mode round #1

This is the logic that supports switching modes via e.g.,
  echo radio > /sys/class/pvrusb2/sn-*/ctl_input/cur_val.

To do the mode switching we need to:
a) broadcast AUDC_SET_RADIO and
b) issue the CX2341X_ENC_MUTE_VIDEO command to the encoder. 

The first is done by adding a new pvr2_i2c_op and having it trigger on 
input change, the second by adding this command in pvr2_encoder_start() 
and requesting an encoder restart on input change by setting 
stale_subsys_mask appropriately. 

The clues about AUDC_SET_RADIO and CX2341X_ENC_MUTE_VIDEO were kindly 
provided by Hans Verkuil on the pvrusb2 mailing list. The idea to 
implement mode switching this way (on input change) is due to Mike Isely.

Why AUDC_SET_RADIO/VIDIOC_S_STD are used for switching? I can 't be sure, 
but I think this can be traced to a cornell student being the first to 
implement radio support in ivtv "as a different standard". I think the 
rest just evolved from there (it 's in the ivtv ML archives).

Signed-off-by: Pantelis Koukousoulas <pakt223@freemail.gr>
Signed-off-by: Mike Isely <isely@pobox.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>
diff --git a/drivers/media/video/pvrusb2/pvrusb2-hdw.c b/drivers/media/video/pvrusb2/pvrusb2-hdw.c
index 503255c..5f6ab99 100644
--- a/drivers/media/video/pvrusb2/pvrusb2-hdw.c
+++ b/drivers/media/video/pvrusb2/pvrusb2-hdw.c
@@ -2260,6 +2260,13 @@
 		stale_subsys_mask |= (1<<PVR2_SUBSYS_B_ENC_CFG);
 	}
 
+	if (hdw->input_dirty) {
+		/* pk: If input changes to or from radio, then the encoder
+		   needs to be restarted (for ENC_MUTE_VIDEO to work) */
+		stale_subsys_mask |= (1<<PVR2_SUBSYS_B_ENC_RUN);
+	}
+
+
 	if (hdw->srate_dirty) {
 		/* Write new sample rate into control structure since
 		 * the master copy is stale.  We must track srate