fat32_base.c

hd driver for S3C44B0。44b0 + ide + fat32.

#include "fat_include.h"


 FAT32_t  FAT32;

//-----------------------------------------------------------------------------
// FAT32_InitLBA: This function is used to find the LBA Address of the first
//				  volume on the disc. Also checks are performed on the signature
//				  and identity codes to make sure the partition is FAT32.
//-----------------------------------------------------------------------------
UI32 FAT32_FindLBABegin(void)
{
		UI8 tempdata;
#ifdef DEBUG_LV0_ON
		UI8 *ch;
		UI16 i;
#endif
		UI32 LBABEGIN;

		
		// Load MBR (LBA 0) into the 512 byte buffer
		IDE_BufferSector(0);	

#ifdef DEBUG_LV0_ON
	//display Sector data
		ch=(UI8*)&(IDE_Internal.currentsector[0]);
	DEBUG_OUT("\n\rIN <FAT32_FindLBABegin> the First Sector(LBA0) is");
	 for(i=0;i<HDD_SECTOR_SIZE;i=i+16)
	  {
	    DEBUG_OUT("\n\rBYTE%4x:%4x%4x%4x%4x%4x%4x%4x%4x%4x%4x%4x%4x%4x%4x%4x%4x",\
	    i, *(ch+i+0), *(ch+i+1), *(ch+i+2), *(ch+i+3), *(ch+i+4), *(ch+i+5), *(ch+i+6), *(ch+i+7),\
	       *(ch+i+8), *(ch+i+9), *(ch+i+10), *(ch+i+11), *(ch+i+12), *(ch+i+13), *(ch+i+14), *(ch+i+15));
	  }
#endif


		// Make Sure 0x55 and 0xAA are at end of sector
	    if (IDE_SectorWord(Signature_Position)!=Signature_Value) 
	   	  {
		  s3c44b0x_Printf("\r\nInvalid MBR, Please Format Drive");
		  s3c44b0x_SysHalt();
		  }
		   
		// Verify Type Code as 0C or 0B for FAT32
		tempdata=IDE_SectorByte(PARTITION1_TYPECODE_LOCATION);
		
		if ((tempdata==FAT32_TYPECODE1)||(tempdata==FAT32_TYPECODE2))
		  	 s3c44b0x_Printf("\r\nValid FAT32 Partition Found");
		else
		  {
		   	 s3c44b0x_Printf("\r\nNon FAT32 Partition Found 0x%x",tempdata);
			 s3c44b0x_SysHalt();
		  }
		  
		// Read LBA Begin for FAT32 File system is located for partition
		LBABEGIN=IDE_SectorUI32(PARTITION1_LBA_BEGIN_LOCATION);
  
  		// Return the LBA address of FAT table
		return LBABEGIN;			
}

//-----------------------------------------------------------------------------
// LBAofCluster: This function converts a cluster number into a sector / LBA 
//				 number.
//-----------------------------------------------------------------------------
UI32 FAT32_LBAofCluster(UI32 Cluster_Number)
{
 return ((FAT32.cluster_begin_lba + ((Cluster_Number-2)*FAT32.SectorsPerCluster)));
}


//-----------------------------------------------------------------------------
// FindFATDetails: Uses FAT32_FindLBABegin to find the LBA for the volume, 
//				   and loads into memory some specific details of the partition
//				   which are used in further calculations.
//-----------------------------------------------------------------------------
void FAT32_FindFAT32Details(void)
{
	 UI8 Number_of_FATS;
	 UI16 Reserved_Sectors;
	 UI32 Sectors_per_FAT;
	 UI32 LBA_BEGIN;
	 
	 LBA_BEGIN = FAT32_FindLBABegin();	// Check Volume 1 and find LBA address
	 IDE_BufferSector(LBA_BEGIN);	// Load Volume 1 table in 'clusterbuffer'
	 
	 // Make sure there are 512 bytes per cluster
	 if (IDE_SectorWord(0x0B)!=0x200) 
	 {
	  	 s3c44b0x_Printf("\r\nError: Bytes per cluster is not 512");
		 s3c44b0x_SysHalt();
	 }

	 // Load Parameters of FAT32	 
 	 FAT32.SectorsPerCluster = IDE_SectorByte(0x0D);
	 Reserved_Sectors = IDE_SectorWord(0x0E);
	 Number_of_FATS = IDE_SectorByte(0x10);
	 Sectors_per_FAT = IDE_SectorUI32(0x24);
	 FAT32.RootDir_First_Cluster = IDE_SectorUI32(0x2C);
	 
	 FAT32.fat_begin_lba = LBA_BEGIN + Reserved_Sectors;	// First FAT LBA address
	 
	 // The address of the first data cluster on this volume
	 FAT32.cluster_begin_lba = FAT32.fat_begin_lba + (Number_of_FATS * Sectors_per_FAT);

	 if (IDE_SectorWord(0x1FE)!=0xAA55) // This signature should be AA55
	 {
	  	 s3c44b0x_Printf("\r\nError: Incorrect Volume Signature");
		  s3c44b0x_SysHalt();
	 } 
}

//-----------------------------------------------------------------------------
// FindNextCluster: Return Cluster number of next cluster in chain by reading
//					FAT table and traversing it. Return 0xffffffff for end of 
//					chain.
//-----------------------------------------------------------------------------
UI32 FAT32_FindNextCluster(UI32 Current_Cluster)
{
	UI32 FAT_sector_offset, UI32position;
	UI32 nextcluster;
	
	// Why is '..' labelled with cluster 0 when it should be 2 ??
	if (Current_Cluster==0) Current_Cluster=2;
	
	// Find which sector of FAT table to read
	FAT_sector_offset = Current_Cluster / 128;
	 
	// Read FAT sector into buffer
	IDE_BufferSector(FAT32.fat_begin_lba+FAT_sector_offset);
	 
	// Find 32 bit entry of current sector relating to cluster number 
	UI32position = (Current_Cluster - (FAT_sector_offset * 128)) * 4; 

	// Read Next Clusters value from Sector Buffer
	nextcluster = IDE_SectorUI32(UI32position);	 

	// Mask out MS 4 bits (its 28bit addressing)
	nextcluster = nextcluster & 0x0FFFFFFF;		
				 
	// If 0x0FFFFFFF then end of chain found
	if (nextcluster==0x0FFFFFFF) 
	   return (0xFFFFFFFF); 
	else 
		 // Else return next cluster
		 return (nextcluster);						 
}