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[media] dvb_frontend: Simplify the emulation logic
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The current logic was broken and too complex; while it works
fine for DVB-S2/DVB-S, it is broken for ISDB-T.
Make the logic simpler, fixes it for ISDB-T and make it clearer.

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
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Mauro Carvalho Chehab committed Mar 18, 2013
1 parent be431b1 commit 52dee39
Showing 1 changed file with 109 additions and 110 deletions.
219 changes: 109 additions & 110 deletions drivers/media/dvb-core/dvb_frontend.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1509,61 +1509,70 @@ static bool is_dvbv3_delsys(u32 delsys)
return status;
}

static int emulate_delivery_system(struct dvb_frontend *fe,
enum dvbv3_emulation_type type,
u32 delsys, u32 desired_system)
/**
* emulate_delivery_system - emulate a DVBv5 delivery system with a DVBv3 type
* @fe: struct frontend;
* @delsys: DVBv5 type that will be used for emulation
*
* Provides emulation for delivery systems that are compatible with the old
* DVBv3 call. Among its usages, it provices support for ISDB-T, and allows
* using a DVB-S2 only frontend just like it were a DVB-S, if the frontent
* parameters are compatible with DVB-S spec.
*/
static int emulate_delivery_system(struct dvb_frontend *fe, u32 delsys)
{
int i;
struct dtv_frontend_properties *c = &fe->dtv_property_cache;

c->delivery_system = delsys;

/*
* The DVBv3 or DVBv5 call is requesting a different system. So,
* emulation is needed.
*
* Emulate newer delivery systems like ISDBT, DVBT and DTMB
* for older DVBv5 applications. The emulation will try to use
* the auto mode for most things, and will assume that the desired
* delivery system is the last one at the ops.delsys[] array
* If the call is for ISDB-T, put it into full-seg, auto mode, TV
*/
dev_dbg(fe->dvb->device,
"%s: Using delivery system %d emulated as if it were a %d\n",
__func__, delsys, desired_system);
if (c->delivery_system == SYS_ISDBT) {
dev_dbg(fe->dvb->device,
"%s: Using defaults for SYS_ISDBT\n",
__func__);

/*
* For now, handles ISDB-T calls. More code may be needed here for the
* other emulated stuff
*/
if (type == DVBV3_OFDM) {
if (c->delivery_system == SYS_ISDBT) {
dev_dbg(fe->dvb->device,
"%s: Using defaults for SYS_ISDBT\n",
__func__);

if (!c->bandwidth_hz)
c->bandwidth_hz = 6000000;

c->isdbt_partial_reception = 0;
c->isdbt_sb_mode = 0;
c->isdbt_sb_subchannel = 0;
c->isdbt_sb_segment_idx = 0;
c->isdbt_sb_segment_count = 0;
c->isdbt_layer_enabled = 0;
for (i = 0; i < 3; i++) {
c->layer[i].fec = FEC_AUTO;
c->layer[i].modulation = QAM_AUTO;
c->layer[i].interleaving = 0;
c->layer[i].segment_count = 0;
}
if (!c->bandwidth_hz)
c->bandwidth_hz = 6000000;

c->isdbt_partial_reception = 0;
c->isdbt_sb_mode = 0;
c->isdbt_sb_subchannel = 0;
c->isdbt_sb_segment_idx = 0;
c->isdbt_sb_segment_count = 0;
c->isdbt_layer_enabled = 7;
for (i = 0; i < 3; i++) {
c->layer[i].fec = FEC_AUTO;
c->layer[i].modulation = QAM_AUTO;
c->layer[i].interleaving = 0;
c->layer[i].segment_count = 0;
}
}
dev_dbg(fe->dvb->device, "%s: change delivery system on cache to %d\n",
__func__, c->delivery_system);
__func__, c->delivery_system);

return 0;
}

/**
* dvbv5_set_delivery_system - Sets the delivery system for a DVBv5 API call
* @fe: frontend struct
* @desired_system: delivery system requested by the user
*
* A DVBv5 call know what's the desired system it wants. So, set it.
*
* There are, however, a few known issues with early DVBv5 applications that
* are also handled by this logic:
*
* 1) Some early apps use SYS_UNDEFINED as the desired delivery system.
* This is an API violation, but, as we don't want to break userspace,
* convert it to the first supported delivery system.
* 2) Some apps might be using a DVBv5 call in a wrong way, passing, for
* example, SYS_DVBT instead of SYS_ISDBT. This is because early usage of
* ISDB-T provided backward compat with DVB-T.
*/
static int dvbv5_set_delivery_system(struct dvb_frontend *fe,
u32 desired_system)
{
Expand All @@ -1578,15 +1587,14 @@ static int dvbv5_set_delivery_system(struct dvb_frontend *fe,
* assume that the application wants to use the first supported
* delivery system.
*/
if (c->delivery_system == SYS_UNDEFINED)
c->delivery_system = fe->ops.delsys[0];
if (desired_system == SYS_UNDEFINED)
desired_system = fe->ops.delsys[0];

/*
* This is a DVBv5 call. So, it likely knows the supported
* delivery systems.
*/

/* Check if the desired delivery system is supported */
* This is a DVBv5 call. So, it likely knows the supported
* delivery systems. So, 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) {
Expand All @@ -1600,69 +1608,85 @@ static int dvbv5_set_delivery_system(struct dvb_frontend *fe,
}

/*
* Need to emulate a delivery system
* The requested delivery system isn't supported. Maybe userspace
* is requesting a DVBv3 compatible delivery system.
*
* The emulation only works if the desired system is one of the
* delivery systems supported by DVBv3 API
*/

type = dvbv3_type(desired_system);

/*
* The delivery system is not supported. See if it can be
* emulated.
* The emulation only works if the desired system is one of the
* DVBv3 delivery systems
*/
if (!is_dvbv3_delsys(desired_system)) {
dev_dbg(fe->dvb->device,
"%s: can't use a DVBv3 FE_SET_FRONTEND call for this frontend\n",
__func__);
"%s: Delivery system %d not supported.\n",
__func__, desired_system);
return -EINVAL;
}

type = dvbv3_type(desired_system);

/*
* Get the last non-DVBv3 delivery system that has the same type
* of the desired system
*/
ncaps = 0;
while (fe->ops.delsys[ncaps] && ncaps < MAX_DELSYS) {
if ((dvbv3_type(fe->ops.delsys[ncaps]) == type) &&
!is_dvbv3_delsys(fe->ops.delsys[ncaps]))
if (dvbv3_type(fe->ops.delsys[ncaps]) == type)
delsys = fe->ops.delsys[ncaps];
ncaps++;
}

/* There's nothing compatible with the desired delivery system */
if (delsys == SYS_UNDEFINED) {
dev_dbg(fe->dvb->device,
"%s: Incompatible DVBv3 FE_SET_FRONTEND call for this frontend\n",
__func__);
"%s: Delivery system %d not supported on emulation mode.\n",
__func__, desired_system);
return -EINVAL;
}

return emulate_delivery_system(fe, type, delsys, desired_system);
dev_dbg(fe->dvb->device,
"%s: Using delivery system %d emulated as if it were %d\n",
__func__, delsys, desired_system);

return emulate_delivery_system(fe, desired_system);
}

/**
* dvbv3_set_delivery_system - Sets the delivery system for a DVBv3 API call
* @fe: frontend struct
*
* A DVBv3 call doesn't know what's the desired system it wants. It also
* doesn't allow to switch between different types. Due to that, userspace
* should use DVBv5 instead.
* However, in order to avoid breaking userspace API, limited backward
* compatibility support is provided.
*
* There are some delivery systems that are incompatible with DVBv3 calls.
*
* This routine should work fine for frontends that support just one delivery
* system.
*
* For frontends that support multiple frontends:
* 1) It defaults to use the first supported delivery system. There's an
* userspace application that allows changing it at runtime;
*
* 2) If the current delivery system is not compatible with DVBv3, it gets
* the first one that it is compatible.
*
* NOTE: in order for this to work with applications like Kaffeine that
* uses a DVBv5 call for DVB-S2 and a DVBv3 call to go back to
* DVB-S, drivers that support both DVB-S and DVB-S2 should have the
* SYS_DVBS entry before the SYS_DVBS2, otherwise it won't switch back
* to DVB-S.
*/
static int dvbv3_set_delivery_system(struct dvb_frontend *fe)
{
int ncaps;
u32 desired_system;
u32 delsys = SYS_UNDEFINED;
struct dtv_frontend_properties *c = &fe->dtv_property_cache;
enum dvbv3_emulation_type type;

/* If not set yet, defaults to the first supported delivery system */
if (c->delivery_system == SYS_UNDEFINED)
c->delivery_system = fe->ops.delsys[0];

/*
* A DVBv3 call doesn't know what's the desired system.
* Also, DVBv3 applications don't know that ops.info->type
* could be changed, and they simply don't tune 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.
*/

/*
* Trivial case: just use the current one, if it already a DVBv3
* delivery system
Expand All @@ -1674,50 +1698,25 @@ static int dvbv3_set_delivery_system(struct dvb_frontend *fe)
return 0;
}

/* Convert from DVBv3 into DVBv5 namespace */
type = dvbv3_type(c->delivery_system);
switch (type) {
case DVBV3_QPSK:
desired_system = SYS_DVBS;
break;
case DVBV3_QAM:
desired_system = SYS_DVBC_ANNEX_A;
break;
case DVBV3_ATSC:
desired_system = SYS_ATSC;
break;
case DVBV3_OFDM:
desired_system = SYS_DVBT;
break;
default:
dev_dbg(fe->dvb->device, "%s: This frontend doesn't support DVBv3 calls\n",
__func__);
return -EINVAL;
}

/*
* Get a delivery system that is compatible with DVBv3
* NOTE: in order for this to work with softwares like Kaffeine that
* uses a DVBv5 call for DVB-S2 and a DVBv3 call to go back to
* DVB-S, drivers that support both should put the SYS_DVBS entry
* before the SYS_DVBS2, otherwise it won't switch back to DVB-S.
* The real fix is that userspace applications should not use DVBv3
* and not trust on calling FE_SET_FRONTEND to switch the delivery
* system.
* Seek for the first delivery system that it is compatible with a
* DVBv3 standard
*/
ncaps = 0;
while (fe->ops.delsys[ncaps] && ncaps < MAX_DELSYS) {
if (fe->ops.delsys[ncaps] == desired_system) {
delsys = desired_system;
if (dvbv3_type(fe->ops.delsys[ncaps]) != DVBV3_UNKNOWN) {
delsys = fe->ops.delsys[ncaps];
break;
}
ncaps++;
}
if (delsys == SYS_UNDEFINED) {
dev_dbg(fe->dvb->device, "%s: Couldn't find a delivery system that matches %d\n",
__func__, desired_system);
dev_dbg(fe->dvb->device,
"%s: Couldn't find a delivery system that works with FE_SET_FRONTEND\n",
__func__);
return -EINVAL;
}
return emulate_delivery_system(fe, type, delsys, desired_system);
return emulate_delivery_system(fe, delsys);
}

static int dtv_property_process_set(struct dvb_frontend *fe,
Expand Down

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