[linux-dvb] Re: Avermedia 771 on Gentoo FIXED!

[Kenneth Aafløy <lists@kenneth.aafloy.net>]

On Wednesday 14 July 2004 04:16, Peter Henderson wrote:
> I think I've fixed it.
>
> There is an  integer underflow bug in mt352.c
> need to change line 517 (based on rev 1.7 in cvs)
> from
>     tmp =  6 * freq + IF_FREQUENCYx6;
> to
>     tmp = ((param->frequency*6)/1000000) + IF_FREQUENCYx6;
>
> This affects any multiplex which is on a Positive or Negative offset.
> (So 4978333330Hz fails but 690000000Hz would be fine)
>
> So Ben this should fix your problem as Crystal Palace is all Pos/Neg
> offsets.

According to the datasheet (* p.44), this calulation is wrong. I've attached a 
patch which corrects this and also adds the requested change below. Please 
test a clean CVS with this patch, as I don't have this card/frontend/dvb-t.

> As  a side note.
> Can FEC_NONE be added as a case to the LP code rate switch statements
> (and probably the HP as well) as this was the original reason I couldnt
> tune anything and had to comment out the default error return.

It will then default to FEC_1_2, is this okay?

Kenneth

* http://assets.zarlink.com/DM/MT352_Design_Manual_Nov03.pdf
Index: mt352.c
===================================================================
RCS file: /cvs/linuxtv/dvb-kernel/linux/drivers/media/dvb/frontends/mt352.c,v
retrieving revision 1.7
diff -u -r1.7 mt352.c
--- mt352.c	8 Jul 2004 17:05:42 -0000	1.7
+++ mt352.c	14 Jul 2004 13:08:38 -0000
@@ -395,6 +395,7 @@
 			break;
 		case FEC_1_2:
 		case FEC_AUTO:
+		case FEC_NONE:
 			break;
 		default:
 			return -EINVAL;
@@ -415,6 +416,7 @@
 			break;
 		case FEC_1_2:
 		case FEC_AUTO:
+		case FEC_NONE:
 			break;
 		default:
 			return -EINVAL;
@@ -514,7 +516,7 @@
 
 	/* here we assume 1/6MHz == 166.66kHz stepsize */
 	#define IF_FREQUENCYx6 217    /* 6 * 36.16666666667MHz */
-	tmp =  6 * freq + IF_FREQUENCYx6;
+	tmp =  6 * (freq + IF_FREQUENCYx6);
 
 	buf[9] = msb(tmp);      /* CHAN_START_(1|0) */
 	buf[10] = lsb(tmp);