Driver question

Driver question

[Elan Feingold]

Hi,

Thanks to all those who helped me get my custom 860 board up and running!
My next question is about mapping some physical memory to user space.  I
have some devices with memory mapped registers.  One of them lives at
0x84000800 (above 2Gb!).  I have been trying to mmap() this into user space
memory, without success (the kernel doesn't like the >2Gb).

>From what I understand, there are usually a few options.  Usually one can
use mmap() -- although I don't know if I can -- or one can write a device
driver to work with kmalloc and friends.

What would be the easiest way to gain access to that physical memory
(non-cached, of course) from user space?  Obviously, it would be nice to map
it in at that very address in user space, but I don't think that's going to
happen.  Any tips would be greatly appreciated, as I'm new to this game.

Best regards,

-elan


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Re: Driver question

[Wolfgang Denk]

In message <NDBBLJKOJGKDOFBHNPGEGEIKCEAA.elan@nxnetworks.com> you wrote:
>
> Thanks to all those who helped me get my custom 860 board up and running!
> My next question is about mapping some physical memory to user space.  I
> have some devices with memory mapped registers.  One of them lives at
> 0x84000800 (above 2Gb!).  I have been trying to mmap() this into user space

That's a physical address, right?

> memory, without success (the kernel doesn't like the >2Gb).

Ummm... you must have been doing something wrong.

> >From what I understand, there are usually a few options.  Usually one can
> use mmap() -- although I don't know if I can -- or one can write a device
> driver to work with kmalloc and friends.

You can use mmap(), but of course  you  need  a  device  driver  that
provides such a mmap() interface.

> What would be the easiest way to gain access to that physical memory
> (non-cached, of course) from user space?  Obviously, it would be nice to map
> it in at that very address in user space, but I don't think that's going to
> happen.  Any tips would be greatly appreciated, as I'm new to this game.

No. You should really use mmap(), but you will end  up  with  virtual
addresses  (a  virtual  kernel  address  in your device driver, and a
virtual user address in  your  application)  which  differ  from  the
physical address.

See drivers/char/ip860_mem.c for examples of how to  export  physical
address  ranges  (in  the  example  it's VMEBus memory) to user level
applications. You can find the file in the kernel sources on our  FTP
server, see
ftp://ftp.denx.de/pub/LinuxPPC/usr/src/linux-2.4.4-2001-07-23.tar.bz2

Wolfgang Denk

--
Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-4596-87  Fax: (+49)-8142-4596-88  Email: wd@denx.de
Certainly there are things in life that money  can't  buy,  but  it's
very funny - Did you ever try buying them without money? - Ogden Nash

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RE: Driver question

[Elan Feingold]

> > One of them lives at 0x84000800 (above 2Gb!).
> That's a physical address, right?

Correct.

> Ummm... you must have been doing something wrong.

Yep, I wasn't page aligning the 0x8400800 8-)  That did it.

> You can use mmap(), but of course  you  need  a  device  driver  that
> provides such a mmap() interface.

It didn't sound like Kenneth was using a device driver (is that correct,
Kenneth?).  Is the driver used to provide additional features (like making
sure the memory is not cached, etc.)?

I'm confused 8-)  Thanks in advance for any help you can provide.

-elan


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driver question

[Dr.-Ing. Erhard Schellmann]

Hi,

I have an DTR 61USB TV Reciever from VESEG GmbH, a German company. For 
this device I need a driver to run it under Ubuntu..
With the device only came a Windows driver. Can anybody help me to find 
such a driver?

Many thanks in advance.

Hardi2000