FpIOCTL

[fabricemg]

Hello, I need help for FpIOCtrl
I want to open 1 DVB-T stick usb with Lazarus.
I use FpIOCTL for open /dev/dvb/adapter0/frontend0 , the result is a FileDescriptor

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fd:= FpOpen('/dev/dvb/adapter0/frontend0', _O_RdWr)
after , i want to acces a data with

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result := FpIOCtl(fd, 61, @dvb_frontend_info)
 dvb_frontend_info have a good definition

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type

  // Frontend type
  // FE_QPSK =  DVB-S
  // FE_QAM = DVB-C
  // FE_OFDM = DVB-T
  fe_type = (
    FE_QPSK,
    FE_QAM,
    FE_OFDM,
    FE_ATSC);

  // frontend capabilities
  fe_caps = (
    FE_IS_STUPID = $0,
    FE_CAN_INVERSION_AUTO = $1,
    FE_CAN_FEC_1_2 = $2,
    FE_CAN_FEC_2_3 = $4,
    FE_CAN_FEC_3_4 = $8,
    FE_CAN_FEC_4_5 = $10,
    FE_CAN_FEC_5_6 = $20,
    FE_CAN_FEC_6_7 = $40,
    FE_CAN_FEC_7_8 = $80,
    FE_CAN_FEC_8_9 = $100,
    FE_CAN_FEC_AUTO = $200,
    FE_CAN_QPSK = $400,
    FE_CAN_QAM_16 = $800,
    FE_CAN_QAM_32 = $1000,
    FE_CAN_QAM_64 = $2000,
    FE_CAN_QAM_128 = $4000,
    FE_CAN_QAM_256 = $8000,
    FE_CAN_QAM_AUTO = $10000,
    FE_CAN_TRANSMISSION_MODE_AUTO = $20000,
    FE_CAN_BANDWIDTH_AUTO = $40000,
    FE_CAN_GUARD_INTERVAL_AUTO = $80000,
    FE_CAN_HIERARCHY_AUTO = $100000,
    FE_CAN_8VSB = $200000,
    FE_CAN_16VSB = $400000,
    FE_HAS_EXTENDED_CAPS = $800000,   // We need more bitspace for newer APIs, indicate this.
    FE_CAN_TURBO_FEC = $8000000,  // frontend supports "turbo fec modulation"
    FE_CAN_2G_MODULATION = $10000000, // frontend supports "2nd generation modulation" (DVB-S2)
    FE_NEEDS_BENDING = $20000000, // not supported anymore, don't use (frontend requires frequency bending)
    FE_CAN_RECOVER = $40000000, // frontend can recover from a cable unplug automatically
    FE_CAN_MUTE_TS = $80000000  // frontend can stop spurious TS data output
    );

  // frontend information
  dvb_frontend_info = record
    Name: array[0..127] of char;
    type_dvb: fe_type;
    frequency_min: cuint32;
    frequency_max: cuint32;
    frequency_stepsize: cuint32;
    frequency_tolerance: cuint32;
    symbol_rate_min: cuint32;
    symbol_rate_max: cuint32;
    symbol_rate_tolerance: cuint32;        // ppm
    notifier_delay: cuint32;           // ms
    caps: fe_caps;
  end;
definition in C is

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#define FE_GET_INFO                _IOR('o', 61, struct dvb_frontend_info)
but I have always result = -1 (error)

a idéa? , where is my mistake?

[ludob]

_IOR is a macro that combines the 3 parameters into 1 integer value. In this case it will translate into

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FE_GET_INFO                 = Integer(-2136445123);

Have a look at this open source VirtualSTBViewer which has many more ioctl constants defined for DVB:
http://www.koders.com/delphi/fidE725487ED90396C9BF3BE407F0FA0B7CE9BE81FD.aspx?s=network

Edit: to be complete, you need to do

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result := FpIOCtl(fd, FE_GET_INFO, @dvb_frontend_info)

[fabricemg]

 Thanks ludob

I have downloaded this project  few days ago, but I don't have seen this unit 

Did you have a information for combine the 3 parameters into 1 integer value?

[ludob]

The definition is in sys/ioctl.h. For example: http://unix.superglobalmegacorp.com/Net2/newsrc/sys/ioctl.h.html (these definitions can change between different *nix systems!)

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#define _IOR(g,n,t) _IOC(IOC_OUT, (g), (n), sizeof(t))
#define _IOC(inout,group,num,len)  (inout | ((len & IOCPARM_MASK) << 16) | ((group) << 8) | (num))
#define IOC_OUT 0x40000000 /* copy out parameters */
#define IOC_IN 0x80000000 /* copy in parameters */
#define IOCPARM_MASK 0x1fff /* parameter length, at most 13 bits */
So _IOR('o', 61, struct dvb_frontend_info) becomes

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$40000000 or (sizeof(dvb_frontend_info) and $1fff) shl 16 or ord('o') shl 8 or 61 =
$40000000 + 168 shl 16 + 111 shl 8 + 61 = $40A86F3D
Now -2136445123 is $80A86F3D which corresponds with _IOW according to above definition.

[fabricemg]

Thank you very much ludob