DDI_UMEM_LOCK(9F) Kernel Functions for Drivers DDI_UMEM_LOCK(9F)

NAME

ddi_umem_lock, ddi_umem_unlock - lock and unlock memory pages

SYNOPSIS

#include <sys/ddi.h>
#include <sys/sunddi.h>

int ddi_umem_lock(caddr_t addr, size_t len, int flags,
ddi_umem_cookie_t *cookiep);


void ddi_umem_unlock(ddi_umem_cookie_t cookie);

INTERFACE LEVEL

illumos DDI specific (illumos DDI)

PARAMETERS

ddi_umem_lock
addr
Virtual address of memory object


len
Length of memory object in bytes


flags
Valid flags include:

DDI_UMEMLOCK_READ
Memory pages are locked to be read
from. (Disk write or a network send.)


DDI_UMEMLOCK_WRITE
Memory pages are locked to be
written to. (Disk read or a network
receive.)


cookiep
Pointer to a kernel memory cookie.


ddi_umem_unlock
cookie
Kernel memory cookie allocated by ddi_umem_lock().

DESCRIPTION

The ddi_umem_lock() function locks down the physical pages (including
I/O pages) that correspond to the current process' virtual address
range [addr, addr + size) and fills in a cookie representing the
locked pages. This cookie can be used to create a buf(9S) structure
that can be used to perform I/O (see ddi_umem_iosetup(9F) and
ddi_dma_buf_bind_handle(9F), or it can be used with
devmap_umem_setup(9F) to export the memory to an application.


The virtual address and length specified must be at a page boundary
and the mapping performed in terms of the system page size. See
pagesize(1).


The flags argument indicates the intended use of the locked memory.
Set flags to DDI_UMEMLOCK_READ if the memory pages will be read (for
example, in a disk write or a network send.) Set flags to
DDI_UMEMLOCK_WRITE if the memory pages will be written (for example,
in a disk read or a network receive). You must choose one (and only
one) of these values.


To unlock the locked pages, the drivers call ddi_umem_unlock(9F) with
the cookie obtained from ddi_umem_lock().


The process is not allowed to exec(2) or fork(2) while its physical
pages are locked down by the device driver.


The device driver must ensure that the physical pages have been
unlocked after the application has called close(2).

RETURN VALUES

On success, a 0 is returned. Otherwise, one of the following errno
values is returned.

EFAULT
User process has no mapping at that address range or does
not support locking


EACCES
User process does not have the required permission.


ENOMEM
The system does not have sufficient resources to lock
memory, or locking len memory would exceed a limit or
resource control on locked memory.


EAGAIN
Could not allocate system resources required to lock the
pages. The ddi_umem_lock() could succeed at a later time.


EINVAL
Requested memory is not aligned on a system page boundary.

CONTEXT

The ddi_umem_lock() function can only be called from user context;
ddi_umem_unlock() from user, kernel, and interrupt contexts.

SEE ALSO

ddi_dma_buf_bind_handle(9F), ddi_umem_alloc(9F),
ddi_umem_iosetup(9F), devmap_umem_setup(9F)

NOTES

The ddi_umem_unlock() function consumes physical memory. The driver
is responsible for a speedy unlock to free up the resources.


The ddi_umem_unlock() function can defer unlocking of the pages to a
later time depending on the implementation.

April 10, 2007 DDI_UMEM_LOCK(9F)