[media] dvb: Allow select between DVB-C Annex A and Annex C

DVB-C, as defined by ITU-T J.83 has 3 annexes. The differences between
Annex A and Annex C is that Annex C uses a subset of the modulation
types, and uses a different rolloff factor. A different rolloff means
that the bandwidth required is slicely different, and may affect the
saw filter configuration at the tuners. Also, some demods have different
configurations, depending on using Annex A or Annex C.

So, allow userspace to specify it, by changing the rolloff factor.
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

Documentation/DocBook/media/dvb/dvbproperty.xml

@@ -311,6 +311,8 @@ typedef enum fe_rolloff {
 	ROLLOFF_20,
 	ROLLOFF_25,
 	ROLLOFF_AUTO,
+	ROLLOFF_15, /* DVB-C Annex A */
+	ROLLOFF_13, /* DVB-C Annex C */
 } fe_rolloff_t;
 		</programlisting>
 		</section>
@@ -778,8 +780,10 @@ typedef enum fe_hierarchy {
 			<listitem><para><link linkend="DTV-MODULATION"><constant>DTV_MODULATION</constant></link></para></listitem>
 			<listitem><para><link linkend="DTV-INVERSION"><constant>DTV_INVERSION</constant></link></para></listitem>
 			<listitem><para><link linkend="DTV-SYMBOL-RATE"><constant>DTV_SYMBOL_RATE</constant></link></para></listitem>
+			<listitem><para><link linkend="DTV-ROLLOFF"><constant>DTV_ROLLOFF</constant></link></para></listitem>
 			<listitem><para><link linkend="DTV-INNER-FEC"><constant>DTV_INNER_FEC</constant></link></para></listitem>
 		</itemizedlist>
+		<para>The Rolloff of 0.15 (ROLLOFF_15) is assumed, as ITU-T J.83 Annex A is more common. For Annex C, rolloff should be 0.13 (ROLLOFF_13). All other values are invalid.</para>
 	</section>
 	<section id="dvbc-annex-b-params">
 		<title>DVB-C Annex B delivery system</title>

drivers/media/dvb/dvb-core/dvb_frontend.c

@@ -876,6 +876,7 @@ static int dvb_frontend_clear_cache(struct dvb_frontend *fe)
 	c->symbol_rate = QAM_AUTO;
 	c->code_rate_HP = FEC_AUTO;
 	c->code_rate_LP = FEC_AUTO;
+	c->rolloff = ROLLOFF_AUTO;
 
 	c->isdbt_partial_reception = -1;
 	c->isdbt_sb_mode = -1;
@@ -1030,6 +1031,7 @@ static void dtv_property_cache_init(struct dvb_frontend *fe,
 		break;
 	case FE_QAM:
 		c->delivery_system = SYS_DVBC_ANNEX_AC;
+		c->rolloff = ROLLOFF_15; /* implied for Annex A */
 		break;
 	case FE_OFDM:
 		c->delivery_system = SYS_DVBT;

include/linux/dvb/frontend.h

@@ -329,6 +329,8 @@ typedef enum fe_rolloff {
 	ROLLOFF_20,
 	ROLLOFF_25,
 	ROLLOFF_AUTO,
+	ROLLOFF_15,	/* DVB-C Annex A */
+	ROLLOFF_13,	/* DVB-C Annex C */
 } fe_rolloff_t;
 
 typedef enum fe_delivery_system {