Read in /dev/port with Segmentation Fault

Read in /dev/port with Segmentation Fault

[scarayol]

Hi all,

I want to access to IO ports on a MPC885. The iopl() is not implemented, in
my distribution, to use inw() outw().
So I use /dev/port. It works for open("/dev/port",..) and lseek() but when
i do a read()  i have a segmentation fault. I gave all the right to
/dev/port
Does anybody have an idea ?
Thanks a lot.

Sophie CARAYOL

Re: Read in /dev/port with Segmentation Fault

[Matt Porter]

On Thu, Jun 09, 2005 at 09:30:43AM +0200, scarayol@assystembrime.com wrote:
> Hi all,
> 
> I want to access to IO ports on a MPC885. The iopl() is not implemented, in
> my distribution, to use inw() outw().
> So I use /dev/port. It works for open("/dev/port",..) and lseek() but when
> i do a read()  i have a segmentation fault. I gave all the right to
> /dev/port
> Does anybody have an idea ?

You are trying to use x86-specific interfaces to x86-specific IO space.
By "IO ports" you must mean memory mapped I/O registers since you are
on PPC. From userspace, use mmap() to map physical address space to a
user virtual address range.

-Matt

Re: Read in /dev/port with Segmentation Fault

[scarayol]

Dear St=E9phane,

Yes i remember your mail about /dev/mem access. But, I never succeed to=

read or write physical memory with reliability so i wrote a driver and =
use
ioremap inside  intead of mmap (before i put all the needed memory on I=
O
memory with the boot command "mem=3DxM" and then it works. So, i think =
i have
some problems with "mmap"  :-).
I think my .../char/mem.c is OK for mmap support.
Why is it necessary to use size+ofs_addr for size and page_addr instead=
 of
physaddr, i thought mmap( ) do it itself ?

Thank you for your help.

Kenavo.

Sophie.




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                    "Fillod Stephane"                                  =
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embrime.com>                                                           =
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: Re: Read in /dev/port with Segmentation  Fault                       =
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Sophie CARAYOL wrote:
>Another question, if i use mmap to map physical addresses of I/O
registers,
>could i dereference the pointer on virtual adresse to access data or
should
>i use read/write on the file descriptor ?

Yes, you can dereference the pointer.
Don't you remember my past mail?

>From the Denx's FAQ (TFQ hits the list monthly) for accessing memory bu=
s:

http://www.denx.de/twiki/bin/view/PPCEmbedded/DeviceDrivers#Section_Acc=
essingPeripheralsFromUserSpace

or shorter: http://tinyurl.com/6c7th

See linux/drivers/char/mem.c to check if mmap support is ok on your arc=
h.

Kenavo
--
St=E9phane



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