[linux-dvb] [PATCH] add DVB-S2 support to frontend.h

Johannes Stezenbach js at linuxtv.org
Wed Mar 1 20:08:46 CET 2006


On Mon, Feb 27, 2006, Marcel Siegert wrote:
>  typedef enum fe_caps {
>  	FE_IS_STUPID			= 0,
> @@ -62,12 +66,13 @@
>  	FE_CAN_HIERARCHY_AUTO		= 0x100000,
>  	FE_CAN_8VSB			= 0x200000,
>  	FE_CAN_16VSB			= 0x400000,
> +	FE_CAN_DVB_S2			= 0x1000000,

This doesn't fit in here. Maybe we can do:

 typedef enum fe_type {
       // values 0 to 3 are reserved for binary compatibilty with old
       // API version
       FE_DVB_S  = (1 << 2),
       FE_DVB_C  = (1 << 3),
       FE_DVB_T  = (1 << 4),
       FE_ATSC   = (1 << 5),
       FE_DVB_S2 = (1 << 6)
 } fe_type_t;

and use that in a GET_CAPS return value so apps can see what
values are legal to pass to FE_SET_STANDARD

#define FE_QPSK   FE_DVB_S // source compatibility
#define FE_QAM    FE_DVB_C
#define FE_OFDM   FE_DVB_T

#define FE_QPSK_OLD 0 // for binary compatibility, handled in drivers,
#define FE_QAM_OLD  1 // should be defined in dvb_frontend.h
#define FE_OFDM_OLD 2
#define FE_ATSC_OLD 3


> +/* backport from dvb-api v4 - adapted a bit to have the last value at bit 31 so we */
> +/* guarantee that the enum will normally have 32 bits size */

What does the "bit 31" comment mean? I think gcc guarantees that
sizeof(enum foo) == sizeof(int), unless you compile with -fshort-enums
(which the kernel doesn't support anyway, I think).

> +/*! describes the available forward error correction code rates. */
> +enum dvb_fe_code_rate {
> +	DVB_FE_FEC_NONE = (1 << 0),
> +	DVB_FE_FEC_1_2  = (1 << 1),
> +	DVB_FE_FEC_2_3  = (1 << 2),
> +	DVB_FE_FEC_3_4  = (1 << 3),
> +	DVB_FE_FEC_4_5  = (1 << 4),
> +	DVB_FE_FEC_5_6  = (1 << 5),
> +	DVB_FE_FEC_6_7  = (1 << 6),
> +	DVB_FE_FEC_7_8  = (1 << 7),
> +	DVB_FE_FEC_8_9  = (1 << 8),
> +	DVB_FE_FEC_3_5	= (1 << 9),
> +	DVB_FE_FEC_9_10	= (1 << 10),
> +	DVB_FE_FEC_AUTO = (1 << 31)
> +};
> +
> +/*! describes the available modulation types. */
> +enum dvb_fe_modulation {
> +	DVB_FE_MOD_QPSK		= (1 << 0),
> +	DVB_FE_MOD_QAM_16	= (1 << 1),
> +	DVB_FE_MOD_QAM_32	= (1 << 2),
> +	DVB_FE_MOD_QAM_64	= (1 << 3),
> +	DVB_FE_MOD_QAM_128	= (1 << 4),
> +	DVB_FE_MOD_QAM_256	= (1 << 5),
> +	DVB_FE_MOD_QAM_AUTO	= (1 << 6),
> +	DVB_FE_MOD_2_VSB	= (1 << 7),
> +	DVB_FE_MOD_4_VSB	= (1 << 8),
> +	DVB_FE_MOD_8_VSB	= (1 << 9),
> +	DVB_FE_MOD_16_VSB	= (1 << 10),
> +	DVB_FE_MOD_8_PSK	= (1 << 11),
> +	DVB_FE_MOD_BPSK		= (1 << 12),
> +	DVB_FE_MOD_MOD_UNKNOWN	= (1 << 31)
> +};
> +
> +/*! describes common supported frontend capabilities. */
> +enum dvb_fe_common_cap {
> +	DVB_FE_CAN_INVERSION_AUTO   = (1 << 0), /*!< fixme */
> +	DVB_FE_CAN_RECOVER          = (1 << 1), /*!< frontend can recover from a cable unplug automatically */
> +	DVB_FE_CAN_MUTE_TS          = (1 << 2), /*!< frontend can stop spurious TS data output */
> +	DVB_FE_SUP_HIGH_LNB_VOLTAGE = (1 << 31), /*!< fixme, frontend can deliver higher lnb voltages */
> +};
> +
> +/*! describes other available, frontend type dependent capabilities. */
> +enum dvb_fe_other_cap {
> +	DVB_FE_CAN_TRANSMISSION_MODE_AUTO = (1 << 0), /*!< fixme (DVB-T specific) */
> +	DVB_FE_CAN_BANDWIDTH_AUTO         = (1 << 1), /*!< fixme (DVB-T specific) */
> +	DVB_FE_CAN_GUARD_INTERVAL_AUTO    = (1 << 2), /*!< fixme (DVB-T specific) */
> +	DVB_FE_CAN_HIERARCHY_AUTO         = (1 << 31), /*!< fixme (DVB-T specific) */
> +};
> +
> +/**
> + *  this struct will be filled by the FE_GET_EXTENDED_INFO ioctl.
> + *  it is a extension to the normal frontend capabilities and provided
> + *  if the dvb_fe_info.caps is having the FE_HAS_EXTENDED_CAN_VALUES bit set.
> + */
> +struct dvb_fe_caps_extended {
> +	enum dvb_fe_code_rate  caps_fec;        /*!< supported fecs */
> +	enum dvb_fe_modulation caps_modulation; /*!< supported modulations */
> +	enum dvb_fe_common_cap caps_common;     /*!< supported common capabilities */
> +	enum dvb_fe_other_cap  caps_other;      /*!< supported other capabilities*/
> +};

I'm not really happy with this. I think it is confusing if we have
e.g. both enum dvb_fe_code_rate and fe_code_rate_t.
Apparently it confuses you, too, as struct dvb_dvbs2_parameters
uses the old one which lacks the DVB-S2 modulation types...

Also, IMHO some of these are caps irrelevant for applications as
dvb-core emulates missing hardware features.

Lastly, the V4 API defines the *GET_CAPS ioctls so that they
are extensible in a way that retains binary compatibilty.

BTW, is there any application which uses the capabilites?
I think apps expect that e.g. a DVB-T frontend can do
all FECs required by the DVB-T standard.


>  struct dvb_frontend_parameters {
> +{
>  	__u32 frequency;     /* (absolute) frequency in Hz for QAM/OFDM/ATSC */
>  			     /* intermediate frequency in kHz for QPSK */
>  	fe_spectral_inversion_t inversion;
>  	union {
> -		struct dvb_qpsk_parameters qpsk;
> -		struct dvb_qam_parameters  qam;
> -		struct dvb_ofdm_parameters ofdm;
> +		struct dvb_dvbs_parameters qpsk;
> +		struct dvb_dvbc_parameters  qam;
> +		struct dvb_dvbt_parameters ofdm;
>  		struct dvb_vsb_parameters vsb;
>  	} u;
> +	/* next is new as previous union was just kept to gain source/binary backwards compatibility */
> +	fe_type_t type;	     /* select which kind of parameters is within the union u. from frontendtype */
> +        struct dvb_frontend_parameters_internal* extended_parameters;
>  };

Wasn't Felix' reasoning that the type field is unnecessary
because of FE_SET_STANDARD?


> +struct __dvb_frontend_event_old {
> +	fe_status_t status;
> +	struct __dvb_frontend_parameters_old parameters;
> +};
>  
>  struct dvb_frontend_event {
> -	fe_status_t status;
> -	struct dvb_frontend_parameters parameters;
> +	fe_status_t status;					/* if Bit 7 (0x80) FE_EXTENDED_TP is SET - you may safely query type and */
> +	struct __dvb_frontend_parameters_old parameters;        /* the extended_parameters */
> +	fe_type_t type; 					/* reflect what type of parameters is contained */
> +	struct dvb_frontend_parameters* extended_parameters;
>  };

Holger Waechtler pointed out in earlier discussions that the
data passed in struct dvb_frontend_event is totally irrelevant,
as it might have been in the event queue for some time and
is thus stale.

Applications should:
- open the frontend device with O_NONBLOCK
- poll() for events
- FE_GET_EVENT all pending events to clear the POLLPRI status,
  and throw them away
- FE_READ_STATUS etc. to get current information

I suggest that we leave FE_GET_EVENT alone and document the
above usage.

> +/**
> + * Struct to keep the api version which can be queried
> + * via the FE_GET_API_VERSION ioctl.
> + * Need for having encapsulation libraries in userspace
> + * possible.
> + */
> +struct dvb_api_version {
> +	__u16	major;
> +	__u16	minor;
> +};

How would an application use this? I think it is
unnecessary, FE_HAS_EXTENDED_CAN_VALUES it enough.


Thanks,
Johannes



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