Why the piece of code determined the disk access mode?

[Jason Luo]

Hi All,

I read the sources of grub 0.94,I found the code in stage2/common.c that 
determin the disk access mode.I'm confused.the code is,

    264       if (get_diskinfo (drive, &geom))
    265         break;
    266
    267       /* Clean out the I/O map.  */
    268       grub_memset ((char *) io_map, 0,
    269                    IO_MAP_SIZE * sizeof (unsigned short));
    270
    271       /* Disable to probe I/O ports temporarily, because this 
doesn't
    272          work with some BIOSes (maybe they are too buggy).  */
    273 #if 0
    274       /* Track the int13 handler.  */
    275       track_int13 (drive);
    276 #endif
    277
    278       /* Set the information.  */
    279       info->drive_number = drive;
    280       info->drive_mode = ((geom.flags & 
BIOSDISK_FLAG_LBA_EXTENSION)
    281                           ? MB_DI_LBA_MODE : MB_DI_CHS_MODE);


geom.flags is 0,The process can not process to line 280. so ,the 
geom.flags is alway larger than or equal to 0.What's the situation 
geom.flags is equal to 0?if geom.flags is  larger than 0,can it determin 
the disk's access mode is LBA ?

thanks!

Jason