linux-kernel - Re: [REGRESSION] Failed network caused by: xhci: switch to pci_alloc_irq

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Date:   Sat, 20 May 2017 09:49:56 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Christoph Hellwig <hch@....de>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        USB list <linux-usb@...r.kernel.org>,
        Mathias Nyman <mathias.nyman@...ux.intel.com>
Subject: Re: [REGRESSION] Failed network caused by: xhci: switch to pci_alloc_irq_vectors

On Fri, May 19, 2017 at 5:46 AM, Christoph Hellwig <hch@....de> wrote:
>
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 33c2b0b77429..5a7fd3b6a7b9 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -1342,7 +1342,7 @@ pci_alloc_irq_vectors_affinity(struct pci_dev *dev, unsigned int min_vecs,
>                                unsigned int max_vecs, unsigned int flags,
>                                const struct irq_affinity *aff_desc)
>  {
> -       if (min_vecs > 1)
> +       if (min_vecs > 1 || !(flags & PCI_IRQ_LEGACY))
>                 return -EINVAL;
>         return 1;
>  }

Side note: why is it doing that " > 1" check, when any value _other_
than 1 is wrong?

Also, to match the non-MSI implementation, wouldn't it be nicer to
just write it that same way (and also verify "dev->irq"):

        if (flags & PCI_IRQ_LEGACY) {
                if (min_vecs == 1 && dev->irq)
                        return 1;
        }
        return -ENOSPC;

(the exact error value probably doesn't matter in practice, but the
CONFIG_MSI case returns ENOSPC by default and that's what
Documentation/PCI/MSI-HOWTO.txt says too).

Hmm?

             Linus