SCO OpenServer

memget(D3oddi)

memget -- allocate contiguous memory at initialization

Synopsis

int memget(int pages);

Description

memget is used to obtain permanent, contiguous, DMAable memory for the driver at initialization time. It is intended for memory that the driver will always have and use rather than for memory that will be used and then released back into the kernel memory pool.

Arguments

pages: memget( ) Amount of memory, measured in pages, to be allocated. Use the btoc(D3oddi) macro to calculate the number of pages from the number of bytes required.

Return values

If successful, memget( ) returns the page frame number of the first frame of memory allocated. Note that this is for kernel virtual space. Use the ctob(D3oddi) macro to translate the return value of memget into a kernel virtual address.

If memget( ) cannot obtains suitable memory, it returns 0 (zero).

Usage

memget( ) always returns physically contiguous, DMAable memory, and should be used only when this is required. If the driver only needs one page of memory, use the sptalloc(D3oddi) function instead.

memget( ) never sleeps, and may return having been unable to allocate physically contiguous memory.

Context and synchronization

Initialization context

Hardware applicability

All

Version applicability

oddi: 1, 2, 2mp, 3, 3mp, 4, 4mp, 5, 5mp, 6, 6mp

SVR5 DDI compatibility

This function is not supported for DDI drivers. See ``Memory allocation'' in HDK Technical Reference for a list of functions that can be used to allocate memory in a DDI driver.

References

btoc(D3oddi), ctob(D3oddi), getcpages(D3oddi), sptalloc(D3oddi)

``Memory allocation'' in HDK Technical Reference

Examples

To obtain a permanent 8KB buffer for a driver, use code such as the following:

   char my_buf_ptr;
   paddr_t my_buf_phys_addr;
   int my_buf_kvpfn;
   
   

   my_buf_kvpfn = (memget(btoc(8192));
   if (my_buf_kvpfn == 0) {
   	cmn_err(CE_NOTE, "My driver: memget() failed");
   } else {
   	my_buf_ptr = (char )ctob(my_buf_kvpfn);
   	my_buf_phys_addr = ktop(my_buf_ptr);
   }