SVR5

dma_pageio(D3)

dma_pageio -- break up an I/O request into manageable units

Synopsis (Not in current DDI version)

   #include <sys/buf.h>
   #include <sys/ddi.h>
   
   void dma_pageio(void (*strat)(), buf_t *bp);

Description

dma_pageio breaks up a data transfer request from physiock(D3) into units of contiguous memory, allowing the memory to be passed to simple DMA controllers that do not support scatter/gather operations.

Arguments

strat: Address of the strategy(D2) routine to call to complete the I/O transfer.
bp: Pointer to the buffer header structure.

Return values

None

Usage

When the transfer completes, any allocated buffers are freed.

Context and synchronization

User or blockable context.

Examples

The following example shows how dma_pageio is used when reading or writing disk data. The driver's read(D2) and write(D2) entry points use physiock to check the validity of the I/O and perform the data transfer. The strategy(D2) routine passed to physiock just calls dma_pageio to perform the data transfer one page at a time.

    1  struct dsize {
    2	daddr_t nblocks;	/* number of blocks in disk partition */
    3	int cyloff;		/* starting cylinder # of partition */
    4  } my_sizes[2] = {
    5	20448, 21,		/* partition 0 = cyl 21-305 */
    6	21888, 1		/* partition 1 = cyl  1-305 */
    7  };

    8  int
    9  my_read(dev, uiop, crp)
   10	dev_t dev;
   11	uio_t *uiop;
   12	cred_t *crp;
   13  {
   14	int nblks;

   15	nblks = my_sizes[getminor(dev)].nblocks;
   16	return(physiock(my_breakup, 0, dev, B_READ, nblks, uiop));
   17  }

   18  int
   19  my_write(dev, uiop, crp)
   20	dev_t dev;
   21	uio_t *uiop;
   22	cred_t *crp;
   23  {
   24	int nblks;

   25	nblks = my_sizes[getminor(dev)].nblocks;
   26	return(physiock(my_breakup, 0, dev, B_WRITE, nblks, uiop));
   27  }

   28  static void
   29  my_breakup(bp)
   30	buf_t *bp;
   31  {
   32	dma_pageio(my_strategy, bp);
   33  }

Hardware applicability

All

Version applicability

ddi: 1, 2, 3, 4

Differences between versions

buf_breakup(D3) replaces dma_pageio.

References

buf(D4), buf_breakup(D3), physiock(D3), read(D2), strategy(D2), write(D2)

``DMA'' in HDK Technical Reference