Allocating a cache-safe buffer for DMA devices and drivers

Allocating a cache-safe buffer for DMA devices and drivers

[Garcia Jérémie]

Hi everybody, I have to port a vxWorks appz to Linux Montavista running =
on a powerPC 405EP based architecture.
In this one, we use the following vxWorks system call: cacheDmaMalloc( ) =
whose man page is :

NAME
    cacheDmaMalloc( ) - allocate a cache-safe buffer for DMA devices and =
drivers

SYNOPSIS
void * cacheDmaMalloc
    (
    size_t bytes              /* number of bytes to allocate */
    )

DESCRIPTION
    This routine returns a pointer to a section of memory that will not =
experience any cache coherency problems. Function pointers in the =
CACHE_FUNCS structure provide access to DMA support routines.

RETURNS
    A pointer to the cache-safe buffer, or NULL.=20


I need to handle the given amount of memory from the user space.=20
So could anyone told how to achieve the same goal on Linux with these =
constraints?

Tks a lot for your precious help!

Re: Allocating a cache-safe buffer for DMA devices and drivers

[Thayumanavar Sachithanantham]

A an equivalent function that does this is pci_alloc_consistent or
dma_alloc_coherent which ensures cache coherency.
Please refer Documentation/DMA-API.txt of the linux source repository.

Thayumanavar S.

On 8/29/05, Garcia J=E9r=E9mie <GARCIAJ@3il.fr> wrote:
> Hi everybody, I have to port a vxWorks appz to Linux Montavista running o=
n a powerPC 405EP based architecture.
> In this one, we use the following vxWorks system call: cacheDmaMalloc( ) =
whose man page is :
>=20
> NAME
>    cacheDmaMalloc( ) - allocate a cache-safe buffer for DMA devices and d=
rivers
>=20
> SYNOPSIS
> void * cacheDmaMalloc
>    (
>    size_t bytes              /* number of bytes to allocate */
>    )
>=20
> DESCRIPTION
>    This routine returns a pointer to a section of memory that will not ex=
perience any cache coherency problems. Function pointers in the CACHE_FUNCS=
 structure provide access to DMA support routines.
>=20
> RETURNS
>    A pointer to the cache-safe buffer, or NULL.
>=20
>=20
> I need to handle the given amount of memory from the user space.
> So could anyone told how to achieve the same goal on Linux with these con=
straints?
>=20
> Tks a lot for your precious help!
>=20
> --
> Kernelnewbies: Help each other learn about the Linux kernel.
> Archive:       http://mail.nl.linux.org/kernelnewbies/
> FAQ:           http://kernelnewbies.org/faq/
>=20
>