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@xxxxxxxxxx>
---
Documentation/DocBook/media/dvb/dvbproperty.xml | 4 ++++
drivers/media/dvb/dvb-core/dvb_frontend.c | 2 ++
include/linux/dvb/frontend.h | 2 ++
3 files changed, 8 insertions(+), 0 deletions(-)
diff --git a/Documentation/DocBook/media/dvb/dvbproperty.xml b/Documentation/DocBook/media/dvb/dvbproperty.xml
index 3bc8a61..6ac8039 100644
--- a/Documentation/DocBook/media/dvb/dvbproperty.xml
+++ b/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>
diff --git a/drivers/media/dvb/dvb-core/dvb_frontend.c b/drivers/media/dvb/dvb-core/dvb_frontend.c
index 2c0acdb..c849455 100644
--- a/drivers/media/dvb/dvb-core/dvb_frontend.c
+++ b/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;
diff --git a/include/linux/dvb/frontend.h b/include/linux/dvb/frontend.h
index 1b1094c..d9251df 100644
--- a/include/linux/dvb/frontend.h
+++ b/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 {
--
1.7.7.1
--
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