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    SubjectRe: [PATCH linux-next v3 1/2] irq: Add CPU mask affinity hint
    On Fri, 30 Apr 2010, Ben Hutchings wrote:
    > On Fri, 2010-04-30 at 13:23 -0700, Peter P Waskiewicz Jr wrote:
    > > +int irq_register_affinity_hint(unsigned int irq, const struct cpumask *m)
    > > +{
    > > + struct irq_desc *desc = irq_to_desc(irq);
    > > + unsigned long flags;
    > > +
    > > + if (!desc)
    > > + return -EINVAL;
    >
    > Is it possible for irq_to_desc(irq) to be NULL? This function already
    > assumes that the caller 'owns' the IRQ.

    Oh come on. Driver writers get everything wrong and not checking on an
    invalid irq number is better than crashing :)

    > > +static int irq_affinity_hint_proc_show(struct seq_file *m, void *v)
    > > +{
    > > + struct irq_desc *desc = irq_to_desc((long)m->private);
    > > + unsigned long flags;
    > > + cpumask_var_t mask;
    > > + int ret = -EINVAL;
    >
    > I don't think this should be returning -EINVAL if the affinity hint is
    > missing. That means 'invalid argument', but there is nothing invalid
    > about trying to read() the corresponding file. The file should simply
    > be empty if there is no hint. (Actually it might be better if it didn't
    > appear at all, but that would be a pain to implement.)

    I agree that -EINVAL is not really a good match.

    How about just returning CPU_MASK_ALL if desc->affinity_hint is not
    set ?

    Thanks,

    tglx


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