linux-kernel - Re: [PATCH] pci: do not try to assign irq 255

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Message-ID: <CAE9FiQWP1F5mLUoHoTHXy-wQoGxVK66QuuHYydaq3YfysS5Etg@mail.gmail.com>
Date:	Tue, 19 Feb 2013 11:40:59 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	Hannes Reinecke <hare@...e.de>, Bjorn Helgaas <bhelgaas@...gle.com>
Cc:	linux-kernel@...r.kernel.org, Frederik Himpe <fhimpe@....ac.be>,
	Oliver Neukum <oneukum@...e.de>,
	David Haerdeman <david@...deman.nu>, linux-usb@...r.kernel.org,
	linux-pci@...r.kernel.org
Subject: Re: [PATCH] pci: do not try to assign irq 255

On Mon, Feb 18, 2013 at 2:09 AM, Hannes Reinecke <hare@...e.de> wrote:
> The PCI config space reseves a byte for the interrupt line,
> so irq 255 actually refers to 'not set'.
> However, the 'irq' field for struct pci_dev is an integer,
> so the original meaning is lost, causing the system to
> assign an interrupt '255', which fails.
>
> So we should _not_ assign an interrupt value here, and
> allow upper layers to fixup things.
>
> This patch make PCI devices with MSI interrupts only
> (like the xhci device on certain HP laptops) work properly.

looks like the bios does not provide _PRT for device in ACPI.

also according to PCI spec, BIOS *must* set interrupt line.

>
> Cc: Frederik Himpe <fhimpe@....ac.be>
> Cc: Oliver Neukum <oneukum@...e.de>
> Cc: David Haerdeman <david@...deman.nu>
> Cc: linux-usb@...r.kernel.org
> Cc: linux-pci@...r.kernel.org
> Signed-off-by: Hannes Reinecke <hare@...e.de>
>
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index 6186f03..a2db887f 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -923,7 +923,8 @@ static void pci_read_irq(struct pci_dev *dev)
>         dev->pin = irq;
>         if (irq)
>                 pci_read_config_byte(dev, PCI_INTERRUPT_LINE, &irq);
> -       dev->irq = irq;
> +       if (irq < 255)
> +               dev->irq = irq;
>  }
>
>  void set_pcie_port_type(struct pci_dev *pdev)
> --
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