Subject: How to fix CHECK warning: testing a 'safe expression'

From: Murali Karicheri <[email-masked]>
Date: Tue, 16 Dec 2014 13:23:00 -0500

netdev maintainers,

I got a comment to address CHECK warning and wondering how to address 
'warning: testing a 'safe expression' which appears when using
IS_ERR_OR_NULL(foo)

where foo is defined as

struct foo_type *foo;

The foo get assigned only NULL or ERR_PTR(error code). So I believe the 
usage is correct. But then how do I make the CHECK happy of its usage?

I have tried doing a grep on the current usage of IS_ERR_OR_NULL() and 
found 276 of them causes this warning in the v3.18 version of the kernel 
that I am using

$ grep -r "warning: testing a 'safe expression" * | wc -l
276

1) Can someone explain what this warning means?

2) Is it acceptable to post patches to netdev list with this warning?

3) if not, how this is expected to be fixed? Any example usage to fix 
this warning will be helpful.

Thanks in advance for
-- 
Murali Karicheri
Linux Kernel, Texas Instruments