That'll fail to compile I bet; at least on i386?

(a) given this is not ERR_PTR (despite it is defined to nothing on FreeBSD) we should add __iomem.

static inline void __iomem *
IOMEM_ERR_PTR(long error)
{
        return (void __iomem *)(intptr_t)error;
}

or if you wish (probably needs linux/err.h then):

#define IOMEM_ERR_PTR(_e) (void __iomem *)ERR_PTR(_e)