dma_buf_vmap(9) [centos man page]

DMA_BUF_VMAP(9) 					   Device drivers infrastructure					   DMA_BUF_VMAP(9)

NAME

       dma_buf_vmap - Create virtual mapping for the buffer object into kernel address space. Same restrictions as for vmap and friends apply.

SYNOPSIS

       void * dma_buf_vmap(struct dma_buf * dmabuf);

ARGUMENTS

       dmabuf
	   [in] buffer to vmap

DESCRIPTION

       This call may fail due to lack of virtual mapping address space. These calls are optional in drivers. The intended use for them is for
       mapping objects linear in kernel space for high use objects. Please attempt to use kmap/kunmap before thinking about these interfaces.

COPYRIGHT

Kernel Hackers Manual 3.10					     June 2014							   DMA_BUF_VMAP(9)

KSEG_TO_PHYS(9r)														  KSEG_TO_PHYS(9r)

NAME

       KSEG_TO_PHYS - General: Converts a kernel-unmapped virtual address to a physical address

SYNOPSIS

       vm_offset_t KSEG_TO_PHYS(
	       vm_offset_t addr );

ARGUMENTS

       Specifies the buffer virtual address to convert to a physical address.

DESCRIPTION

       The  KSEG_TO_PHYS  routine  converts  a	kernel-unmapped virtual address to a kernel physical address. Device drivers can use this physical
       address in DMA operations. Prior to calling KSEG_TO_PHYS, device driver writers often call one  of  the	following  routines  to  determine
       whether the address passed is a virtual address in the addressed kernel segment: IS_KSEG_VA

	      Determines if the specified address is located in the kernel-unmapped address space.  IS_SEG0_VA

	      Determines if the specified address is located in the user-mapped address space.	IS_SEG1_VA

	      Determines if the specified address is located in the kernel-mapped address space.

RETURN VALUES

       Upon successful completion, KSEG_TO_PHYS returns the physical address.

EXAMPLE

       The following code fragment shows a call to KSEG_TO_PHYS:

       .  .  .

       caddr_t virt_addr;  [1] unsigned phys_addr; [2]

       .  .  .

	   if(IS_KSEG_VA(virt_addr)) { [3]
	       phys_addr = KSEG_TO_PHYS(virt_addr); [4]

       .  .  .

       Declares  a  variable  to  store  the  user  buffer's  virtual  address.   Declares  a  variable  to store the physical address returned by
       KSEG_TO_PHYS.  Before calling KSEG_TO_PHYS, calls IS_KSEG_VA to determine if the virtual address is from the kernel-unmapped address space.
       If  the virtual address is from the kernel-unmapped address space, then calls KSEG_TO_PHYS to convert the address to a corresponding physi-
       cal address.

SEE ALSO

       Routines: IS_KSEG_VA(9r), PHYS_TO_KSEG(9r)

																  KSEG_TO_PHYS(9r)