inverse mmap() available?

inverse mmap() available?

[Norbert Roos]

Hello!

Is there a way to map user space memory into kernel address space, e.g.
that i don't have to call get_user(var,...) but simply use var =
*user_space_ptr?

What i intend to do (as the next step) is to DMA-transfer data directly
between a PCI device and user space memory. The buffer in user space
should be allocated with malloc(), so allocating a buffer in kernel and
mmap()-ping it to user space is not the solution..

I guess this has been asked before, any links to further information
would be great.

Thanks
Norbert

Re: inverse mmap() available?

[Tommy Reynolds]

Norbert Roos <n.roos@berlin.de> was pleased to say:

> 
> Hello!
> 
> Is there a way to map user space memory into kernel address space, e.g.
> that i don't have to call get_user(var,...) but simply use var =
> *user_space_ptr?
> 
> What i intend to do (as the next step) is to DMA-transfer data directly
> between a PCI device and user space memory. The buffer in user space
> should be allocated with malloc(), so allocating a buffer in kernel and
> mmap()-ping it to user space is not the solution..
> 
> I guess this has been asked before, any links to further information
> would be great.

Look at the KIOBUF stuff in <linux/iobuf.h> for how to do this.

---------------------------------------------+-----------------------------
Tommy Reynolds                               | mailto:	<reynolds@redhat.com>
Red Hat, Inc., Embedded Development Services | Phone:  +1.256.704.9286
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Senior Software Developer                    | Mobile: +1.919.641.2923

Re: inverse mmap() available?

[Christoph Hellwig]

In article <3BB49438.1F2C59B3@berlin.de> you wrote:

> Hello!
>
> Is there a way to map user space memory into kernel address space, e.g.
> that i don't have to call get_user(var,...) but simply use var =
> *user_space_ptr?
>
> What i intend to do (as the next step) is to DMA-transfer data directly
> between a PCI device and user space memory. The buffer in user space
> should be allocated with malloc(), so allocating a buffer in kernel and
> mmap()-ping it to user space is not the solution..
>
> I guess this has been asked before, any links to further information
> would be great.

map_user_kiobuf is what you want :) Some more explanation at:

 ftp://ftp.openlinux.org/pub/people/hch/kio/kiobuf.txt

putting a user program to sleep till interrupted

[Anil Kumar]

hi,
I wanted to know how a user program/process can be put
to sleep by using the functions given in the kernel. I
will be calling the function not from user space but
from kernel space, i.e. from inside the kernel. I also
want to be able to start it again whenever required.
I went thru sched.c but couldn't figure out how to
make my own wait list.
Thanx in advance.
Anil

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Re: putting a user program to sleep till interrupted

[Martin Maletinsky]

Hello,

A good explanation is found in:
http://www.linuxdoc.org/LDP/lki/lki-2.html#ss2.5

and also in Chapter 5, 'Linux Device Drivers' from Alessandro Rubini & Jonathan Corbet
(you find an electronic version of the book in http://www.oreilly.com/catalog/linuxdrive2/)

regards
Martin

Anil Kumar wrote:

> hi,
> I wanted to know how a user program/process can be put
> to sleep by using the functions given in the kernel. I
> will be calling the function not from user space but
> from kernel space, i.e. from inside the kernel. I also
> want to be able to start it again whenever required.
> I went thru sched.c but couldn't figure out how to
> make my own wait list.
> Thanx in advance.
> Anil
>
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