# Re: how to check for "optional" ppc chip features (MSR\_BE)

- From: Benjamin Herrenschmidt \<benh@kernel.crashing.org\>
- Date: 2008-05-04 21:45:56 
- List: linuxppc-dev
- Page: https://ratatoskr.run/linuxppc-dev/2008/05/9439678
- Thread: https://ratatoskr.run/linuxppc-dev/2008/05/9439597/t.md

```text

On Thu, 2008-05-01 at 22:48 -0500, Kumar Gala wrote:
> 
> Look at arch/powerpc/kernel/cputable.c to see how we handle issues  
> like this.
> 

Oh and classic pitfall: If you define a new feature bit, make sure
CPU_FTRS_POSSIBLE is updated to contain it in cputable.h

Also, It may not be totally clear, but:

PPC_FEATURE_* are exposed to userspace via AT_HWCAP

CPU_FTR_* are kernel internal (and can be used for runtime patching of
assembly code).

Ben.
```