Re: [microblaze-uclinux] Low level access

[Benny Chen <bennyc@xxxxxxxxxxxxxx>]

Hi Duy-ky,
Without hardware MMU support it is even more important for your 
application code to access your ipcore via the IOCTL() command.  This is 
so because it would help prevent your application code from bringing 
down the kernel when it does incorrect memory access due to pointer 
referencing error.

The recommended way is to write a thin driver for your ipcore and 
provide access to the application program via the device file interface.

If you like the idea of referencing memory via their address instead of 
IOCTL then look at mmap() support for your driver.

Cheers,
B,

Duy-Ky Nguyen wrote:
> Hello,
>
> I got some experiences on low level access in Linux using X86 and 
> MPC8272. They were "real Linux" with memory protection between kernel 
> and user space, so I had to go through ioctl for low level access.
>
> I'm quite aware that uCLinux does not have that kind of protection. In 
> experience, loose something goes together with gain some thing, so I 
> expect I'm able to have more direct access of low level.
>
> Let's say I have a user_ip at 0x40080000, I've created a new myapp_hw 
> in user-apps, and failed to compile a code using
>
> // Start of code
> #include <asm/io.h>
> #define BASEADDR 0x40080000
> . .
> x = inl((volatile unsigned *) (BASEADDR));    // read-only reg
> outl(1, (volatile unsigned *) (BASEADDR));    // write 1 to RWreg
> ..
> // End of code
>
> I had very long list of error from the compilation.
>
> I'd really appreciate if I'd be shown how to use these low-level IO 
> access functions.
>
> Thanks a lot,
>
> Duy-Ky
>
>
>
>
>
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