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Commit 37fa53c6 authored by Mauro Carvalho Chehab's avatar Mauro Carvalho Chehab
Browse files

[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: default avatarMauro Carvalho Chehab <mchehab@redhat.com>
parent 9474c5e6

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

+18 −9
Original line number Diff line number Diff line
@@ -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