[media] DVB: Query DVB frontend delivery capabilities

Currently, for any multi-standard frontend it is assumed that it just
has a single standard capability. This is fine in some cases, but
makes things hard when there are incompatible standards in conjuction.
Eg: DVB-S can be seen as a subset of DVB-S2, but the same doesn't hold
the same for DSS. This is not specific to any driver as it is, but a
generic issue. This was handled correctly in the multiproto tree,
while such functionality is missing from the v5 API update.

http://www.linuxtv.org/pipermail/vdr/2008-November/018417.html

Later on a FE_CAN_2G_MODULATION was added as a hack to workaround this
issue in the v5 API, but that hack is incapable of addressing the
issue, as it can be used to simply distinguish between DVB-S and
DVB-S2 alone, or another X vs X2 modulation. If there are more systems,
then you have a potential issue.

An application needs to query the device capabilities before requesting
any operation from the device.

Signed-off-by: Manu Abraham <[e-mail]>
Acked-by: Andreas Oberritter <[e-mail]>
Acked-by: Oliver Endriss <[e-mail]>
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>

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

···
 	_DTV_CMD(DTV_GUARD_INTERVAL, 0, 0),
 	_DTV_CMD(DTV_TRANSMISSION_MODE, 0, 0),
 	_DTV_CMD(DTV_HIERARCHY, 0, 0),
+
+	_DTV_CMD(DTV_ENUM_DELSYS, 0, 0),
 };
 
 static void dtv_property_dump(struct dtv_property *tvp)
···
 static int dvb_frontend_ioctl_properties(struct file *file,
 			unsigned int cmd, void *parg);
 
+static void dtv_set_default_delivery_caps(const struct dvb_frontend *fe, struct dtv_property *p)
+{
+	const struct dvb_frontend_info *info = &fe->ops.info;
+	u32 ncaps = 0;
+
+	switch (info->type) {
+	case FE_QPSK:
+		p->u.buffer.data[ncaps++] = SYS_DVBS;
+		if (info->caps & FE_CAN_2G_MODULATION)
+			p->u.buffer.data[ncaps++] = SYS_DVBS2;
+		if (info->caps & FE_CAN_TURBO_FEC)
+			p->u.buffer.data[ncaps++] = SYS_TURBO;
+		break;
+	case FE_QAM:
+		p->u.buffer.data[ncaps++] = SYS_DVBC_ANNEX_AC;
+		break;
+	case FE_OFDM:
+		p->u.buffer.data[ncaps++] = SYS_DVBT;
+		if (info->caps & FE_CAN_2G_MODULATION)
+			p->u.buffer.data[ncaps++] = SYS_DVBT2;
+		break;
+	case FE_ATSC:
+		if (info->caps & (FE_CAN_8VSB | FE_CAN_16VSB))
+			p->u.buffer.data[ncaps++] = SYS_ATSC;
+		if (info->caps & (FE_CAN_QAM_16 | FE_CAN_QAM_64 | FE_CAN_QAM_128 | FE_CAN_QAM_256))
+			p->u.buffer.data[ncaps++] = SYS_DVBC_ANNEX_B;
+		break;
+	}
+	p->u.buffer.len = ncaps;
+}
+
 static int dtv_property_process_get(struct dvb_frontend *fe,
 				    struct dtv_property *tvp,
 				    struct file *file)
···
 	}
 
 	switch(tvp->cmd) {
+	case DTV_ENUM_DELSYS:
+		dtv_set_default_delivery_caps(fe, tvp);
+		break;
 	case DTV_FREQUENCY:
 		tvp->u.data = c->frequency;
 		break;

include/linux/dvb/frontend.h

···
 
 #define DTV_DVBT2_PLP_ID	43
 
-#define DTV_MAX_COMMAND				DTV_DVBT2_PLP_ID
+#define DTV_ENUM_DELSYS		44
+
+#define DTV_MAX_COMMAND				DTV_ENUM_DELSYS
 
 typedef enum fe_pilot {
 	PILOT_ON,

include/linux/dvb/version.h

···
 #define _DVBVERSION_H_
 
 #define DVB_API_VERSION 5
-#define DVB_API_VERSION_MINOR 4
+#define DVB_API_VERSION_MINOR 5
 
 #endif /*_DVBVERSION_H_*/