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Darwin 0.2 Driver Kit

			Floppy disk param notes
			
Current driver

fd_attach_com {

	recal, abort if error (do some retries);
	get status (MID, WP, etc.);
	get struct fd_disk_info (fd_format_info.fd_disk_info) via MID;
	for(fd_format_info.density_info.density= 4 to 1) {
		seek to read_id_cyl (should ++);
		if read_id works
			goto found_dens;
	}
	
    found_dens:
	if density = none {
	    	disk unformatted:
		
	    	// get defaults for density, sect_size
	    	density = fd_format_info.fd_disk_info.max_density; 
		sect_size = fd_get_sectsize_info(density)[0].sect_size
		set_density_info(density); 
		set_sector_size(sect_size);
		return;
	}
	
	mark disk as formatted to allow reading;
	for each legal sect_size for the fd_sectsize_info for this density {
		set_sector_size(sect_size);
		do a retry loop {
			read(test_sector++);
			if good
				goto found_sect_size;
		}		
	}
	mark disk unformatted;
	return;
	
    found_sect_size:
    	return good;
	
}

set_density_info(int density) 
{
	// don't have to save sect_size; sectsize_info won't change by the 
	// time we need it...
	
	save current sect_size from fd_format_info.sectsize_info.sect_size;
	find fd_density_info for spec'd density, write it to
		fd_format_info.density_info;
	set_sect_size(saved_sect_size);
	if density == none
		mark disk unformatted;
}

set_sect_size(sect_size) 
{
	validate that this sect_size is legal for current 
		fd_format_info.density_info;
	set fd_format_info.sectsize_info;
	set disk formatted;
}

.........................

what are all of these weird structs?

fd_disk_info (fd_disk_info_t): fd_extern.h
	maps media_id to tracks_per_cyl and num_cylinders.
	One per media_id in fdDiskInfo[].

fd_sectsize_info (fd_sectsize_info_t): fd_extern.h
	contains ector size, 82077 sector size codem sects_per_track, gap.
	One of these for each legal density/sectsize combo in ssi_Xmb[].

fd_density_info (fd_density_info_t) : fd_extern.h 
	Maps density to capacity and mfm.
	One per density in fdDensityInfo[].
	
fd_format_info (fd_format_info_t, fdFormatInfo_t) : fd_extern.h
	Contains all current info about inserted disk. 
	fd_disk_info, fd_density_info, fd_sectsize_info, total_sects, flags.
	Obtained via ioctl(FDIOCGFORM).
	
fdDensitySectsize_t : FloppyTypes.h
	maps density to an array of legal fd_sectsize_info's.
	One per legal density in fdDensitySectsize[].
	
fdDriveInfo_t : FloppyPublic.h
	drive_info (for ioctl(DKIOCGINFO)), seek, settle, unload time.
	One per drive type (only one) in fdDriveInfo[].
	

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