arch/mips/include/asm/dma.h - linux - Git at Google

 /* SPDX-License-Identifier: GPL-2.0 */
 /*
  * linux/include/asm/dma.h: Defines for using and allocating dma channels.
  * Written by Hennus Bergman, 1992.
  * High DMA channel support & info by Hannu Savolainen
  * and John Boyd, Nov. 1992.
  *
  * NOTE: all this is true *only* for ISA/EISA expansions on Mips boards
  * and can only be used for expansion cards. Onboard DMA controllers, such
  * as the R4030 on Jazz boards behave totally different!
  */

 #ifndef _ASM_DMA_H
 #define _ASM_DMA_H

 #include <asm/io.h>			/* need byte IO */
 #include <linux/spinlock.h>		/* And spinlocks */
 #include <linux/delay.h>


 #ifdef HAVE_REALLY_SLOW_DMA_CONTROLLER
 #define dma_outb	outb_p
 #else
 #define dma_outb	outb
 #endif

 #define dma_inb		inb

 /*
  * NOTES about DMA transfers:
  *
  *  controller 1: channels 0-3, byte operations, ports 00-1F
  *  controller 2: channels 4-7, word operations, ports C0-DF
  *
  *  - ALL registers are 8 bits only, regardless of transfer size
  *  - channel 4 is not used - cascades 1 into 2.
  *  - channels 0-3 are byte - addresses/counts are for physical bytes
  *  - channels 5-7 are word - addresses/counts are for physical words
  *  - transfers must not cross physical 64K (0-3) or 128K (5-7) boundaries
  *  - transfer count loaded to registers is 1 less than actual count
  *  - controller 2 offsets are all even (2x offsets for controller 1)
  *  - page registers for 5-7 don't use data bit 0, represent 128K pages
  *  - page registers for 0-3 use bit 0, represent 64K pages
  *
  * DMA transfers are limited to the lower 16MB of _physical_ memory.
  * Note that addresses loaded into registers must be _physical_ addresses,
  * not logical addresses (which may differ if paging is active).
  *
  *  Address mapping for channels 0-3:
  *
  *   A23 ... A16 A15 ... A8  A7 ... A0	  (Physical addresses)
  *    |	 ...  |	  |  ... |   |	... |
  *    |	 ...  |	  |  ... |   |	... |
  *    |	 ...  |	  |  ... |   |	... |
  *   P7	 ...  P0  A7 ... A0  A7 ... A0
  * |	Page	| Addr MSB | Addr LSB |	  (DMA registers)
  *
  *  Address mapping for channels 5-7:
  *
  *   A23 ... A17 A16 A15 ... A9 A8 A7 ... A1 A0	   (Physical addresses)
  *    |	 ...  |	  \   \	  ... \	 \  \  ... \  \
  *    |	 ...  |	   \   \   ... \  \  \	... \  (not used)
  *    |	 ...  |	    \	\   ... \  \  \	 ... \
  *   P7	 ...  P1 (0) A7 A6  ... A0 A7 A6 ... A0
  * |	  Page	    |  Addr MSB	  |  Addr LSB  |   (DMA registers)
  *
  * Again, channels 5-7 transfer _physical_ words (16 bits), so addresses
  * and counts _must_ be word-aligned (the lowest address bit is _ignored_ at
  * the hardware level, so odd-byte transfers aren't possible).
  *
  * Transfer count (_not # bytes_) is limited to 64K, represented as actual
  * count - 1 : 64K => 0xFFFF, 1 => 0x0000.  Thus, count is always 1 or more,
  * and up to 128K bytes may be transferred on channels 5-7 in one operation.
  *
  */

 #ifndef CONFIG_GENERIC_ISA_DMA_SUPPORT_BROKEN
 #define MAX_DMA_CHANNELS	8
 #endif

 /*
  * The maximum address in KSEG0 that we can perform a DMA transfer to on this
  * platform.  This describes only the PC style part of the DMA logic like on
  * Deskstations or Acer PICA but not the much more versatile DMA logic used
  * for the local devices on Acer PICA or Magnums.
  */
 #if defined(CONFIG_SGI_IP22) || defined(CONFIG_SGI_IP28)
 /* don't care; ISA bus master won't work, ISA slave DMA supports 32bit addr */
 #define MAX_DMA_ADDRESS		PAGE_OFFSET
 #else
 #define MAX_DMA_ADDRESS		(PAGE_OFFSET + 0x01000000)
 #endif
 #define MAX_DMA_PFN		PFN_DOWN(virt_to_phys((void *)MAX_DMA_ADDRESS))

 #ifndef MAX_DMA32_PFN
 #define MAX_DMA32_PFN		(1UL << (32 - PAGE_SHIFT))
 #endif

 /* 8237 DMA controllers */
 #define IO_DMA1_BASE	0x00	/* 8 bit slave DMA, channels 0..3 */
 #define IO_DMA2_BASE	0xC0	/* 16 bit master DMA, ch 4(=slave input)..7 */

 /* DMA controller registers */
 #define DMA1_CMD_REG		0x08	/* command register (w) */
 #define DMA1_STAT_REG		0x08	/* status register (r) */
 #define DMA1_REQ_REG		0x09	/* request register (w) */
 #define DMA1_MASK_REG		0x0A	/* single-channel mask (w) */
 #define DMA1_MODE_REG		0x0B	/* mode register (w) */
 #define DMA1_CLEAR_FF_REG	0x0C	/* clear pointer flip-flop (w) */
 #define DMA1_TEMP_REG		0x0D	/* Temporary Register (r) */
 #define DMA1_RESET_REG		0x0D	/* Master Clear (w) */
 #define DMA1_CLR_MASK_REG	0x0E	/* Clear Mask */
 #define DMA1_MASK_ALL_REG	0x0F	/* all-channels mask (w) */

 #define DMA2_CMD_REG		0xD0	/* command register (w) */
 #define DMA2_STAT_REG		0xD0	/* status register (r) */
 #define DMA2_REQ_REG		0xD2	/* request register (w) */
 #define DMA2_MASK_REG		0xD4	/* single-channel mask (w) */
 #define DMA2_MODE_REG		0xD6	/* mode register (w) */
 #define DMA2_CLEAR_FF_REG	0xD8	/* clear pointer flip-flop (w) */
 #define DMA2_TEMP_REG		0xDA	/* Temporary Register (r) */
 #define DMA2_RESET_REG		0xDA	/* Master Clear (w) */
 #define DMA2_CLR_MASK_REG	0xDC	/* Clear Mask */
 #define DMA2_MASK_ALL_REG	0xDE	/* all-channels mask (w) */

 #define DMA_ADDR_0		0x00	/* DMA address registers */
 #define DMA_ADDR_1		0x02
 #define DMA_ADDR_2		0x04
 #define DMA_ADDR_3		0x06
 #define DMA_ADDR_4		0xC0
 #define DMA_ADDR_5		0xC4
 #define DMA_ADDR_6		0xC8
 #define DMA_ADDR_7		0xCC

 #define DMA_CNT_0		0x01	/* DMA count registers */
 #define DMA_CNT_1		0x03
 #define DMA_CNT_2		0x05
 #define DMA_CNT_3		0x07
 #define DMA_CNT_4		0xC2
 #define DMA_CNT_5		0xC6
 #define DMA_CNT_6		0xCA
 #define DMA_CNT_7		0xCE

 #define DMA_PAGE_0		0x87	/* DMA page registers */
 #define DMA_PAGE_1		0x83
 #define DMA_PAGE_2		0x81
 #define DMA_PAGE_3		0x82
 #define DMA_PAGE_5		0x8B
 #define DMA_PAGE_6		0x89
 #define DMA_PAGE_7		0x8A

 #define DMA_MODE_READ	0x44	/* I/O to memory, no autoinit, increment, single mode */
 #define DMA_MODE_WRITE	0x48	/* memory to I/O, no autoinit, increment, single mode */
 #define DMA_MODE_CASCADE 0xC0	/* pass thru DREQ->HRQ, DACK<-HLDA only */

 #define DMA_AUTOINIT	0x10

 extern spinlock_t  dma_spin_lock;

 static __inline__ unsigned long claim_dma_lock(void)
 {
 	unsigned long flags;
 	spin_lock_irqsave(&dma_spin_lock, flags);
 	return flags;
 }

 static __inline__ void release_dma_lock(unsigned long flags)
 {
 	spin_unlock_irqrestore(&dma_spin_lock, flags);
 }

 /* enable/disable a specific DMA channel */
 static __inline__ void enable_dma(unsigned int dmanr)
 {
 	if (dmanr<=3)
 		dma_outb(dmanr,	 DMA1_MASK_REG);
 	else
 		dma_outb(dmanr & 3,  DMA2_MASK_REG);
 }

 static __inline__ void disable_dma(unsigned int dmanr)
 {
 	if (dmanr<=3)
 		dma_outb(dmanr | 4,  DMA1_MASK_REG);
 	else
 		dma_outb((dmanr & 3) | 4,  DMA2_MASK_REG);
 }

 /* Clear the 'DMA Pointer Flip Flop'.
  * Write 0 for LSB/MSB, 1 for MSB/LSB access.
  * Use this once to initialize the FF to a known state.
  * After that, keep track of it. :-)
  * --- In order to do that, the DMA routines below should ---
  * --- only be used while holding the DMA lock ! ---
  */
 static __inline__ void clear_dma_ff(unsigned int dmanr)
 {
 	if (dmanr<=3)
 		dma_outb(0,  DMA1_CLEAR_FF_REG);
 	else
 		dma_outb(0,  DMA2_CLEAR_FF_REG);
 }

 /* set mode (above) for a specific DMA channel */
 static __inline__ void set_dma_mode(unsigned int dmanr, char mode)
 {
 	if (dmanr<=3)
 		dma_outb(mode | dmanr,	DMA1_MODE_REG);
 	else
 		dma_outb(mode | (dmanr&3),  DMA2_MODE_REG);
 }

 /* Set only the page register bits of the transfer address.
  * This is used for successive transfers when we know the contents of
  * the lower 16 bits of the DMA current address register, but a 64k boundary
  * may have been crossed.
  */
 static __inline__ void set_dma_page(unsigned int dmanr, char pagenr)
 {
 	switch(dmanr) {
 		case 0:
 			dma_outb(pagenr, DMA_PAGE_0);
 			break;
 		case 1:
 			dma_outb(pagenr, DMA_PAGE_1);
 			break;
 		case 2:
 			dma_outb(pagenr, DMA_PAGE_2);
 			break;
 		case 3:
 			dma_outb(pagenr, DMA_PAGE_3);
 			break;
 		case 5:
 			dma_outb(pagenr & 0xfe, DMA_PAGE_5);
 			break;
 		case 6:
 			dma_outb(pagenr & 0xfe, DMA_PAGE_6);
 			break;
 		case 7:
 			dma_outb(pagenr & 0xfe, DMA_PAGE_7);
 			break;
 	}
 }


 /* Set transfer address & page bits for specific DMA channel.
  * Assumes dma flipflop is clear.
  */
 static __inline__ void set_dma_addr(unsigned int dmanr, unsigned int a)
 {
 	set_dma_page(dmanr, a>>16);
 	if (dmanr <= 3)	 {
 	    dma_outb( a & 0xff, ((dmanr&3)<<1) + IO_DMA1_BASE );
 	    dma_outb( (a>>8) & 0xff, ((dmanr&3)<<1) + IO_DMA1_BASE );
 	}  else	 {
 	    dma_outb( (a>>1) & 0xff, ((dmanr&3)<<2) + IO_DMA2_BASE );
 	    dma_outb( (a>>9) & 0xff, ((dmanr&3)<<2) + IO_DMA2_BASE );
 	}
 }


 /* Set transfer size (max 64k for DMA0..3, 128k for DMA5..7) for
  * a specific DMA channel.
  * You must ensure the parameters are valid.
  * NOTE: from a manual: "the number of transfers is one more
  * than the initial word count"! This is taken into account.
  * Assumes dma flip-flop is clear.
  * NOTE 2: "count" represents _bytes_ and must be even for channels 5-7.
  */
 static __inline__ void set_dma_count(unsigned int dmanr, unsigned int count)
 {
 	count--;
 	if (dmanr <= 3)	 {
 	    dma_outb( count & 0xff, ((dmanr&3)<<1) + 1 + IO_DMA1_BASE );
 	    dma_outb( (count>>8) & 0xff, ((dmanr&3)<<1) + 1 + IO_DMA1_BASE );
 	} else {
 	    dma_outb( (count>>1) & 0xff, ((dmanr&3)<<2) + 2 + IO_DMA2_BASE );
 	    dma_outb( (count>>9) & 0xff, ((dmanr&3)<<2) + 2 + IO_DMA2_BASE );
 	}
 }


 /* Get DMA residue count. After a DMA transfer, this
  * should return zero. Reading this while a DMA transfer is
  * still in progress will return unpredictable results.
  * If called before the channel has been used, it may return 1.
  * Otherwise, it returns the number of _bytes_ left to transfer.
  *
  * Assumes DMA flip-flop is clear.
  */
 static __inline__ int get_dma_residue(unsigned int dmanr)
 {
 	unsigned int io_port = (dmanr<=3)? ((dmanr&3)<<1) + 1 + IO_DMA1_BASE
 					 : ((dmanr&3)<<2) + 2 + IO_DMA2_BASE;

 	/* using short to get 16-bit wrap around */
 	unsigned short count;

 	count = 1 + dma_inb(io_port);
 	count += dma_inb(io_port) << 8;

 	return (dmanr<=3)? count : (count<<1);
 }


 /* These are in kernel/dma.c: */
 extern int request_dma(unsigned int dmanr, const char * device_id);	/* reserve a DMA channel */
 extern void free_dma(unsigned int dmanr);	/* release it again */

 #endif /* _ASM_DMA_H */
	/* SPDX-License-Identifier: GPL-2.0 */
	/*
	* linux/include/asm/dma.h: Defines for using and allocating dma channels.
	* Written by Hennus Bergman, 1992.
	* High DMA channel support & info by Hannu Savolainen
	* and John Boyd, Nov. 1992.
	*
	* NOTE: all this is true only for ISA/EISA expansions on Mips boards
	* and can only be used for expansion cards. Onboard DMA controllers, such
	* as the R4030 on Jazz boards behave totally different!
	*/

	#ifndef _ASM_DMA_H
	#define _ASM_DMA_H

	#include <asm/io.h> /* need byte IO */
	#include <linux/spinlock.h> /* And spinlocks */
	#include <linux/delay.h>


	#ifdef HAVE_REALLY_SLOW_DMA_CONTROLLER
	#define dma_outb outb_p
	#else
	#define dma_outb outb
	#endif

	#define dma_inb inb

	/*
	* NOTES about DMA transfers:
	*
	* controller 1: channels 0-3, byte operations, ports 00-1F
	* controller 2: channels 4-7, word operations, ports C0-DF
	*
	* - ALL registers are 8 bits only, regardless of transfer size
	* - channel 4 is not used - cascades 1 into 2.
	* - channels 0-3 are byte - addresses/counts are for physical bytes
	* - channels 5-7 are word - addresses/counts are for physical words
	* - transfers must not cross physical 64K (0-3) or 128K (5-7) boundaries
	* - transfer count loaded to registers is 1 less than actual count
	* - controller 2 offsets are all even (2x offsets for controller 1)
	* - page registers for 5-7 don't use data bit 0, represent 128K pages
	* - page registers for 0-3 use bit 0, represent 64K pages
	*
	* DMA transfers are limited to the lower 16MB of _physical_ memory.
	* Note that addresses loaded into registers must be _physical_ addresses,
	* not logical addresses (which may differ if paging is active).
	*
	* Address mapping for channels 0-3:
	*
	* A23 ... A16 A15 ... A8 A7 ... A0 (Physical addresses)
	* \| ... \| \| ... \| \| ... \|
	* \| ... \| \| ... \| \| ... \|
	* \| ... \| \| ... \| \| ... \|
	* P7 ... P0 A7 ... A0 A7 ... A0
	* \| Page \| Addr MSB \| Addr LSB \| (DMA registers)
	*
	* Address mapping for channels 5-7:
	*
	* A23 ... A17 A16 A15 ... A9 A8 A7 ... A1 A0 (Physical addresses)
	* \| ... \| \ \ ... \ \ \ ... \ \
	* \| ... \| \ \ ... \ \ \ ... \ (not used)
	* \| ... \| \ \ ... \ \ \ ... \
	* P7 ... P1 (0) A7 A6 ... A0 A7 A6 ... A0
	* \| Page \| Addr MSB \| Addr LSB \| (DMA registers)
	*
	* Again, channels 5-7 transfer _physical_ words (16 bits), so addresses
	* and counts _must_ be word-aligned (the lowest address bit is _ignored_ at
	* the hardware level, so odd-byte transfers aren't possible).
	*
	* Transfer count (_not # bytes_) is limited to 64K, represented as actual
	* count - 1 : 64K => 0xFFFF, 1 => 0x0000. Thus, count is always 1 or more,
	* and up to 128K bytes may be transferred on channels 5-7 in one operation.
	*
	*/

	#ifndef CONFIG_GENERIC_ISA_DMA_SUPPORT_BROKEN
	#define MAX_DMA_CHANNELS 8
	#endif

	/*
	* The maximum address in KSEG0 that we can perform a DMA transfer to on this
	* platform. This describes only the PC style part of the DMA logic like on
	* Deskstations or Acer PICA but not the much more versatile DMA logic used
	* for the local devices on Acer PICA or Magnums.
	*/
	#if defined(CONFIG_SGI_IP22) \|\| defined(CONFIG_SGI_IP28)
	/* don't care; ISA bus master won't work, ISA slave DMA supports 32bit addr */
	#define MAX_DMA_ADDRESS PAGE_OFFSET
	#else
	#define MAX_DMA_ADDRESS (PAGE_OFFSET + 0x01000000)
	#endif
	#define MAX_DMA_PFN PFN_DOWN(virt_to_phys((void *)MAX_DMA_ADDRESS))

	#ifndef MAX_DMA32_PFN
	#define MAX_DMA32_PFN (1UL << (32 - PAGE_SHIFT))
	#endif

	/* 8237 DMA controllers */
	#define IO_DMA1_BASE 0x00 /* 8 bit slave DMA, channels 0..3 */
	#define IO_DMA2_BASE 0xC0 /* 16 bit master DMA, ch 4(=slave input)..7 */

	/* DMA controller registers */
	#define DMA1_CMD_REG 0x08 /* command register (w) */
	#define DMA1_STAT_REG 0x08 /* status register (r) */
	#define DMA1_REQ_REG 0x09 /* request register (w) */
	#define DMA1_MASK_REG 0x0A /* single-channel mask (w) */
	#define DMA1_MODE_REG 0x0B /* mode register (w) */
	#define DMA1_CLEAR_FF_REG 0x0C /* clear pointer flip-flop (w) */
	#define DMA1_TEMP_REG 0x0D /* Temporary Register (r) */
	#define DMA1_RESET_REG 0x0D /* Master Clear (w) */
	#define DMA1_CLR_MASK_REG 0x0E /* Clear Mask */
	#define DMA1_MASK_ALL_REG 0x0F /* all-channels mask (w) */

	#define DMA2_CMD_REG 0xD0 /* command register (w) */
	#define DMA2_STAT_REG 0xD0 /* status register (r) */
	#define DMA2_REQ_REG 0xD2 /* request register (w) */
	#define DMA2_MASK_REG 0xD4 /* single-channel mask (w) */
	#define DMA2_MODE_REG 0xD6 /* mode register (w) */
	#define DMA2_CLEAR_FF_REG 0xD8 /* clear pointer flip-flop (w) */
	#define DMA2_TEMP_REG 0xDA /* Temporary Register (r) */
	#define DMA2_RESET_REG 0xDA /* Master Clear (w) */
	#define DMA2_CLR_MASK_REG 0xDC /* Clear Mask */
	#define DMA2_MASK_ALL_REG 0xDE /* all-channels mask (w) */

	#define DMA_ADDR_0 0x00 /* DMA address registers */
	#define DMA_ADDR_1 0x02
	#define DMA_ADDR_2 0x04
	#define DMA_ADDR_3 0x06
	#define DMA_ADDR_4 0xC0
	#define DMA_ADDR_5 0xC4
	#define DMA_ADDR_6 0xC8
	#define DMA_ADDR_7 0xCC

	#define DMA_CNT_0 0x01 /* DMA count registers */
	#define DMA_CNT_1 0x03
	#define DMA_CNT_2 0x05
	#define DMA_CNT_3 0x07
	#define DMA_CNT_4 0xC2
	#define DMA_CNT_5 0xC6
	#define DMA_CNT_6 0xCA
	#define DMA_CNT_7 0xCE

	#define DMA_PAGE_0 0x87 /* DMA page registers */
	#define DMA_PAGE_1 0x83
	#define DMA_PAGE_2 0x81
	#define DMA_PAGE_3 0x82
	#define DMA_PAGE_5 0x8B
	#define DMA_PAGE_6 0x89
	#define DMA_PAGE_7 0x8A

	#define DMA_MODE_READ 0x44 /* I/O to memory, no autoinit, increment, single mode */
	#define DMA_MODE_WRITE 0x48 /* memory to I/O, no autoinit, increment, single mode */
	#define DMA_MODE_CASCADE 0xC0 /* pass thru DREQ->HRQ, DACK<-HLDA only */

	#define DMA_AUTOINIT 0x10

	extern spinlock_t dma_spin_lock;

	static __inline__ unsigned long claim_dma_lock(void)
	{
	unsigned long flags;
	spin_lock_irqsave(&dma_spin_lock, flags);
	return flags;
	}

	static __inline__ void release_dma_lock(unsigned long flags)
	{
	spin_unlock_irqrestore(&dma_spin_lock, flags);
	}

	/* enable/disable a specific DMA channel */
	static __inline__ void enable_dma(unsigned int dmanr)
	{
	if (dmanr<=3)
	dma_outb(dmanr, DMA1_MASK_REG);
	else
	dma_outb(dmanr & 3, DMA2_MASK_REG);
	}

	static __inline__ void disable_dma(unsigned int dmanr)
	{
	if (dmanr<=3)
	dma_outb(dmanr \| 4, DMA1_MASK_REG);
	else
	dma_outb((dmanr & 3) \| 4, DMA2_MASK_REG);
	}

	/* Clear the 'DMA Pointer Flip Flop'.
	* Write 0 for LSB/MSB, 1 for MSB/LSB access.
	* Use this once to initialize the FF to a known state.
	* After that, keep track of it. :-)
	* --- In order to do that, the DMA routines below should ---
	* --- only be used while holding the DMA lock ! ---
	*/
	static __inline__ void clear_dma_ff(unsigned int dmanr)
	{
	if (dmanr<=3)
	dma_outb(0, DMA1_CLEAR_FF_REG);
	else
	dma_outb(0, DMA2_CLEAR_FF_REG);
	}

	/* set mode (above) for a specific DMA channel */
	static __inline__ void set_dma_mode(unsigned int dmanr, char mode)
	{
	if (dmanr<=3)
	dma_outb(mode \| dmanr, DMA1_MODE_REG);
	else
	dma_outb(mode \| (dmanr&3), DMA2_MODE_REG);
	}

	/* Set only the page register bits of the transfer address.
	* This is used for successive transfers when we know the contents of
	* the lower 16 bits of the DMA current address register, but a 64k boundary
	* may have been crossed.
	*/
	static __inline__ void set_dma_page(unsigned int dmanr, char pagenr)
	{
	switch(dmanr) {
	case 0:
	dma_outb(pagenr, DMA_PAGE_0);
	break;
	case 1:
	dma_outb(pagenr, DMA_PAGE_1);
	break;
	case 2:
	dma_outb(pagenr, DMA_PAGE_2);
	break;
	case 3:
	dma_outb(pagenr, DMA_PAGE_3);
	break;
	case 5:
	dma_outb(pagenr & 0xfe, DMA_PAGE_5);
	break;
	case 6:
	dma_outb(pagenr & 0xfe, DMA_PAGE_6);
	break;
	case 7:
	dma_outb(pagenr & 0xfe, DMA_PAGE_7);
	break;
	}
	}


	/* Set transfer address & page bits for specific DMA channel.
	* Assumes dma flipflop is clear.
	*/
	static __inline__ void set_dma_addr(unsigned int dmanr, unsigned int a)
	{
	set_dma_page(dmanr, a>>16);
	if (dmanr <= 3) {
	dma_outb( a & 0xff, ((dmanr&3)<<1) + IO_DMA1_BASE );
	dma_outb( (a>>8) & 0xff, ((dmanr&3)<<1) + IO_DMA1_BASE );
	} else {
	dma_outb( (a>>1) & 0xff, ((dmanr&3)<<2) + IO_DMA2_BASE );
	dma_outb( (a>>9) & 0xff, ((dmanr&3)<<2) + IO_DMA2_BASE );
	}
	}


	/* Set transfer size (max 64k for DMA0..3, 128k for DMA5..7) for
	* a specific DMA channel.
	* You must ensure the parameters are valid.
	* NOTE: from a manual: "the number of transfers is one more
	* than the initial word count"! This is taken into account.
	* Assumes dma flip-flop is clear.
	* NOTE 2: "count" represents _bytes_ and must be even for channels 5-7.
	*/
	static __inline__ void set_dma_count(unsigned int dmanr, unsigned int count)
	{
	count--;
	if (dmanr <= 3) {
	dma_outb( count & 0xff, ((dmanr&3)<<1) + 1 + IO_DMA1_BASE );
	dma_outb( (count>>8) & 0xff, ((dmanr&3)<<1) + 1 + IO_DMA1_BASE );
	} else {
	dma_outb( (count>>1) & 0xff, ((dmanr&3)<<2) + 2 + IO_DMA2_BASE );
	dma_outb( (count>>9) & 0xff, ((dmanr&3)<<2) + 2 + IO_DMA2_BASE );
	}
	}


	/* Get DMA residue count. After a DMA transfer, this
	* should return zero. Reading this while a DMA transfer is
	* still in progress will return unpredictable results.
	* If called before the channel has been used, it may return 1.
	* Otherwise, it returns the number of _bytes_ left to transfer.
	*
	* Assumes DMA flip-flop is clear.
	*/
	static __inline__ int get_dma_residue(unsigned int dmanr)
	{
	unsigned int io_port = (dmanr<=3)? ((dmanr&3)<<1) + 1 + IO_DMA1_BASE
	: ((dmanr&3)<<2) + 2 + IO_DMA2_BASE;

	/* using short to get 16-bit wrap around */
	unsigned short count;

	count = 1 + dma_inb(io_port);
	count += dma_inb(io_port) << 8;

	return (dmanr<=3)? count : (count<<1);
	}


	/* These are in kernel/dma.c: */
	extern int request_dma(unsigned int dmanr, const char * device_id); /* reserve a DMA channel */
	extern void free_dma(unsigned int dmanr); /* release it again */

	#endif /* _ASM_DMA_H */