On Wed, Jan 09, 2013 at 10:35:22AM +0000, Arnd Bergmann wrote:
> On Wednesday 09 January 2013, Alexandre Courbot wrote:
> > On Tue, Jan 8, 2013 at 9:59 PM, Arnd Bergmann <a...@arndb.de> wrote:
> > > Please avoid the use of IS_ERR_OR_NULL(), especially on interfaces you
> > > introduce yourself. AFAICT, gpiod_get cannot return NULL, so you
> > > should not check for that.
> >
> > Sure - you sound like IS_ERR_OR_NULL() is generally considered evil,
>
> Correct.
>
> > may I ask why this is the case?
>
> It's very hard to get right: either you are interested in the error code,
> and then you don't have one in some cases, or you don't care but have
> to check for it anyway. When you define a function, just make it clear
> what the expected return values are, either NULL for error or a negative
> ERR_PTR value, but not both.
Indeed, and any code which does this:
if (IS_ERR_OR_NULL(ptr))
return PTR_ERR(ptr);
is buggy because on NULL it returns 0, which is generally accepted as being
"success".
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