Messages in this thread | | | Date | Mon, 16 Jun 2014 21:49:03 +0300 | From | Dan Carpenter <> | Subject | Re: [PATCH 3/5] staging/wlags49_h2: correct check of the return value of register_netdev() |
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On Mon, Jun 16, 2014 at 04:50:51PM +0200, Stephan Gabert wrote: > As mentioned in net/core/dev.c register_netdev() explicitly returns a > negative errno code on failure. > > So in case of failure, one should rather test whether ret is negative > than just unlike 0.
No. In the kernel the normal way is to say:
if (ret) return ret;
Zero is succes and non-zero is error code.
if (ret != 0) return ret;
That's a double negative and pointlessly confusing.
if (ret != 0 != 0 != 0)
That's a hextuple negative and awesomely confusing.
There are times where a double negative is ok. When you are talking about numbers specifically:
if (ret != 0 && ret != 3) {
That means ret is not zero or three, but zero doesn't mean success or failure, it's just a number.
For strcmp() functions you should always compare against zero because that is the idiom.
if (strcmp(foo, bar) < 0) if (strcmp(foo, bar) != 0)
The first "<" means "foo" is before "bar" and "!=" means not equal.
if (ret < 0) return ret;
Probably means that now ret is either zero or a positive value??? It is ambiguous.
regards, dan carpenter
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