From 37fa53c6a13ac9e82f9c6d334862b514e34de2a4 Mon Sep 17 00:00:00 2001
From: Mauro Carvalho Chehab <mchehab@redhat.com>
Date: Thu, 5 Jan 2012 14:39:05 -0200
Subject: [PATCH] [media] dvb_frontend: improve documentation on
set_delivery_system()
While this patch change some things, the updated fields there are
used just on printk, so it shouldn't cause any functional changes.
Yet, this routine is a little complex, so explain a little more
how it works.
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
---
drivers/media/dvb/dvb-core/dvb_frontend.c | 27 +++++++++++++++--------
1 file changed, 18 insertions(+), 9 deletions(-)
diff --git a/drivers/media/dvb/dvb-core/dvb_frontend.c b/drivers/media/dvb/dvb-core/dvb_frontend.c
index 128f67715ad7..0e079a1a4f49 100644
--- a/drivers/media/dvb/dvb-core/dvb_frontend.c
+++ b/drivers/media/dvb/dvb-core/dvb_frontend.c
@@ -1440,9 +1440,13 @@ static int set_delivery_system(struct dvb_frontend *fe, u32 desired_system)
if (desired_system == SYS_UNDEFINED) {
/*
* A DVBv3 call doesn't know what's the desired system.
- * So, don't change the current delivery system. Instead,
- * find the closest DVBv3 system that matches the delivery
- * system.
+ * Also, DVBv3 applications don't know that ops.info->type
+ * could be changed, and they simply dies when it doesn't
+ * match.
+ * So, don't change the current delivery system, as it
+ * may be trying to do the wrong thing, like setting an
+ * ISDB-T frontend as DVB-T. Instead, find the closest
+ * DVBv3 system that matches the delivery system.
*/
if (is_dvbv3_delsys(c->delivery_system)) {
dprintk("%s() Using delivery system to %d\n",
@@ -1452,27 +1456,29 @@ static int set_delivery_system(struct dvb_frontend *fe, u32 desired_system)
type = dvbv3_type(c->delivery_system);
switch (type) {
case DVBV3_QPSK:
- desired_system = FE_QPSK;
+ desired_system = SYS_DVBS;
break;
case DVBV3_QAM:
- desired_system = FE_QAM;
+ desired_system = SYS_DVBC_ANNEX_A;
break;
case DVBV3_ATSC:
- desired_system = FE_ATSC;
+ desired_system = SYS_ATSC;
break;
case DVBV3_OFDM:
- desired_system = FE_OFDM;
+ desired_system = SYS_DVBT;
break;
default:
dprintk("%s(): This frontend doesn't support DVBv3 calls\n",
__func__);
return -EINVAL;
}
- delsys = c->delivery_system;
} else {
/*
- * Check if the desired delivery system is supported
+ * This is a DVBv5 call. So, it likely knows the supported
+ * delivery systems.
*/
+
+ /* Check if the desired delivery system is supported */
ncaps = 0;
while (fe->ops.delsys[ncaps] && ncaps < MAX_DELSYS) {
if (fe->ops.delsys[ncaps] == desired_system) {
@@ -1518,6 +1524,9 @@ static int set_delivery_system(struct dvb_frontend *fe, u32 desired_system)
}
/*
+ * The DVBv3 or DVBv5 call is requesting a different system. So,
+ * emulation is needed.
+ *
* Emulate newer delivery systems like ISDBT, DVBT and DMBTH
* for older DVBv5 applications. The emulation will try to use
* the auto mode for most things, and will assume that the desired
--
2.20.1