[Libcdio-devel] mmc_get_disc_erasable proposition + questions

[Frank Endres]

Hi !

I followed suggestions to avoid unneeded "fat" status-retrieving by MMC
operation. Wwat do You think about it ?
/**
  Retrieves MMC DISC_INFO_DATA.

  @param p_cdio the CD object to be acted upon.

  @param i_status, on return will be set indicate whether the operation was
  a success (DRIVER_OP_SUCCESS) or if not to some other value.

  @param mmc_disc_info_data, if *mmc_disc_info_data is NULL, an MMC command
  will be performed to retrieve the data, else, nothing will be done. Free
when
  no longer needed.
 */
void
mmc_get_disc_info_data_if_null( const CdIo_t *p_cdio,
                           driver_return_code_t *i_status,
               uint8_t **mmc_disc_info_data) {
    mmc_cdb_t cdb = {{0, }};

    if (*mmc_disc_info_data == NULL) {
    *mmc_disc_info_data = (uint8_t*) malloc (MMC_DISC_INFO_DATA_SIZE *
sizeof (uint8_t));
    memset (*mmc_disc_info_data, 0, MMC_DISC_INFO_DATA_SIZE);
    CDIO_MMC_SET_COMMAND (cdb.field, CDIO_MMC_GPCMD_READ_DISC_INFO);
    CDIO_MMC_SET_READ_LENGTH8 (cdb.field, MMC_DISC_INFO_DATA_SIZE);

    *i_status = mmc_run_cmd (p_cdio, 0, &cdb, SCSI_MMC_DATA_READ,
                MMC_DISC_INFO_DATA_SIZE, *mmc_disc_info_data);
    } else {
    i_status = DRIVER_OP_SUCCESS;
    }
}


/**
  Detects if a disc (CD or DVD) is erasable or not.

  @param p_cdio the CD object to be acted upon.

  @param opt_i_status, if not NULL, on return will be set indicate whether
  the operation was a success (DRIVER_OP_SUCCESS) or if not to some
  other value.

  @param mmc_disc_info_data, if *mmc_disc_info_data is NULL, an MMC command
  will be performed to retrieve the data, else, the available data will be
  used. Free when no longer needed.

  @return true if the disc is detected as erasable (rewritable), false
  otherwise.
 */
bool
    mmc_get_disc_erasable( const CdIo_t *p_cdio,
                           driver_return_code_t *opt_i_status,
               uint8_t **mmc_disc_info_data) {
    driver_return_code_t i_status;

    mmc_get_disc_info_data_if_null (p_cdio, &i_status, mmc_disc_info_data);
    if (opt_i_status != NULL) *opt_i_status = i_status;

    return (DRIVER_OP_SUCCESS == i_status) ?
        (((*mmc_disc_info_data)[2] & 0x10) ? true : false)
        : false;
}


/**
  Detects if a disc (CD or DVD) is empy or not.

  @param p_cdio the CD object to be acted upon.

  @param opt_i_status, if not NULL, on return will be set indicate whether
  the operation was a success (DRIVER_OP_SUCCESS) or if not to some
  other value.

  @param mmc_disc_info_data, if *mmc_disc_info_data is NULL, an MMC command
  will be performed to retrieve the data, else, the available data will be
  used. Free when no longer needed.

  @return true if the disc is detected as empty, false otherwise.
 */
bool
    mmc_get_disc_empty( const CdIo_t *p_cdio,
                           driver_return_code_t *opt_i_status,
              uint8_t **mmc_disc_info_data) {
    driver_return_code_t i_status;

    mmc_get_disc_info_data_if_null (p_cdio, &i_status, mmc_disc_info_data);
    if (opt_i_status != NULL) *opt_i_status = i_status;

    return (DRIVER_OP_SUCCESS == i_status) ?
        (((*mmc_disc_info_data)[2] & 0x03 == 0x00) ? true : false)
        : false;
}


I also have one question: I have a DVD+R (Verbatim) that is not detected as
a DVD by the cdio_is_discmode_dvd function. for this media, discmode is
CDIO_DISCMODE_DVD_OTHER. Maybe You have a good reason to do so, but would it
be possible to change this function ?
bool
cdio_is_discmode_dvd(discmode_t discmode)
{
  switch (discmode) {
  case CDIO_DISC_MODE_DVD_ROM:
  case CDIO_DISC_MODE_DVD_RAM:
  case CDIO_DISC_MODE_DVD_R:
  case CDIO_DISC_MODE_DVD_RW:
  case CDIO_DISC_MODE_DVD_PR:
  case CDIO_DISC_MODE_DVD_PRW:
  case CDIO_DISC_MODE_DVD_OTHER:
    return true;
  default:
    return false;
  }
}


My intention is to write a simple "mmc_get_disc_information" function using
mmc commands and cdio/iso9660 functions (cdio_get_discmode =>
mmc_get_discmode, cdio_is_discmode_dvd, cdio_get_disc_last_lsn
=>mmc_get_disc_last_lsn, cdio_guess_cd_type, iso9660_fs_read_pvd). Is it OK
? Here are the data types I propose:
typedef enum {
    GENERIC_DISC_MODE_ERROR, //also used when no media is detected
    GENERIC_DISC_MODE_CD,
    GENERIC_DISC_MODE_DVD,
    //GENERIC_DISC_MODE_BD
} generic_disctype_t;

typedef struct {
    track_t num;
    cdio_fs_t fs_type;
    uint32_t size;
} track_info_t;

typedef struct {
    generic_disctype_t type;
    bool empty;
    bool rewritable;
    uint32_t size; //0 if empty
    uint32_t capacity; //for writable media only
    uint8_t tracks_count;
    track_info_t* tracks;
} disc_information_t;

As You can see, my intention is too give "High Level" information only, to
simplify programmers work (my point of view is a burning application). I
hope You are still interested.

Best Regards !


-- 
Frank Endres