[linux-dvb] Re: disable zigzag scan?

[Johannes Stezenbach <js@linuxtv.org>]

Carlo E. Prelz wrote:
> Quoting Gerd Knorr (kraxel@bytesex.org):
> 
> > Is there some way to disable the fe zigzag scanning?
> 
> I had posted a patch ages ago, but it has not been accepted into the
> mainstream... I need to disable zigzagging when fine-pointing my
> tripod-mounted dish.

> +#define FE_ZIGZAG                  _IO('o', 79)
> +#define FE_DONT_ZIGZAG             _IO('o', 80)

IIRC I was against your approach because it sets global state
that changes the behaviour of all future tuning attempts.
At the mimimum you should reset the zigzag state to the default
when the frontend device is closed.

But actually I would prefer an API like the following
(completely untested, but I believe it is binary compatible):

Index: linux/include/linux/dvb/frontend.h
===================================================================
RCS file: /cvs/linuxtv/dvb-kernel/linux/include/linux/dvb/frontend.h,v
retrieving revision 1.17
diff -u -p -r1.17 frontend.h
--- linux/include/linux/dvb/frontend.h	16 Dec 2004 15:45:54 -0000	1.17
+++ linux/include/linux/dvb/frontend.h	12 Jan 2005 23:10:29 -0000
@@ -221,10 +221,15 @@ struct dvb_ofdm_parameters {
 };
 
 
+#define FE_INVERSION_MASK 3
+#define FE_NO_ZIGZAG (1 << 2)
 struct dvb_frontend_parameters {
 	__u32 frequency;     /* (absolute) frequency in Hz for QAM/OFDM/ATSC */
 			     /* intermediate frequency in kHz for QPSK */
-	fe_spectral_inversion_t inversion;
+	union {
+		fe_spectral_inversion_t inversion; /* for backward compat */
+		int flags;
+	};
 	union {
 		struct dvb_qpsk_parameters qpsk;
 		struct dvb_qam_parameters  qam;

Comments?

Johannes