SCO OpenServer

db_read(D3oddi)

db_read -- transfer data from physical memory to a user address

Synopsis

   void db_read(struct devbuf *dv, caddr_t va, unsigned count);

Description

db_read transfers data from physical contiguous memory allocated by the db_alloc(D3oddi) function to a virtual user address.

Arguments

count: Amount of data, in bytes, to be transferred.
dv: Pointer to the devbuf structure; see db_alloc(D3oddi).
va: User virtual address to which to copy the data.

Return values

None.

Usage

Only use this routine after the requested pages are locked into memory by a previous call to physio(D3oddi). Use of db_read under any other circumstances results in a panic.

Context and synchronization

User context.

Hardware applicability

All

Version applicability

oddi: 1, 2

Differences between versions

Current drivers that allocate memory with the getcpages(D3oddi) function can use the copyout(D3oddi) function to transfer the data.

SVR5 DDI compatibility

This function is not supported in DDI. Rewrite the driver to use a different memory allocation scheme, then use the copyout(D3) function to move the data.

References

db_alloc(D3oddi), db_write(D3oddi), physio(D3oddi)

Examples

The following example shows how to transfer data from dv to a user buffer:

   struct buf *bp;
   struct devbuf dv;
   
   db_read( &dv, paddr(bp), bp->b_count );