[media] dvb_frontend: Simplify the emulation logic

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>

1 files changed, 109 insertions, 110 deletions

diff --git a/drivers/media/dvb-core/dvb_frontend.c b/drivers/media/dvb-core/dvb_frontend.c
index d0d193d1404a..eaa0a74e6a87 100644
--- a/drivers/media/dvb-core/dvb_frontend.c
+++ b/drivers/media/dvb-core/dvb_frontend.c
@@ -1509,9 +1509,17 @@ 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;
@@ -1519,51 +1527,52 @@ static int emulate_delivery_system(struct dvb_frontend *fe,
         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)
 {
@@ -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) {
@@ -1600,70 +1608,86 @@ 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
          */
@@ -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,