man/man9f/ddi_umem_lock.9f

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 DDI_UMEM_LOCK 9F "Apr 10, 2007"
 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.