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

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Date:	Tue, 26 Feb 2013 14:29:05 +0100
From:	David Härdeman <david@...deman.nu>
To:	Hannes Reinecke <hare@...e.de>
Cc:	Yinghai Lu <yinghai@...nel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	linux-kernel@...r.kernel.org, Frederik Himpe <fhimpe@....ac.be>,
	Oliver Neukum <oneukum@...e.de>, linux-usb@...r.kernel.org,
	linux-pci@...r.kernel.org
Subject: Re: [PATCH] pci: do not try to assign irq 255

On Thu, Feb 21, 2013 at 07:53:14AM +0100, Hannes Reinecke wrote:
>On 02/20/2013 05:57 PM, Yinghai Lu wrote:
>>it seems you mess pin with interrupt line.
>>
>>current code:
>>         unsigned char irq;
>>
>>         pci_read_config_byte(dev, PCI_INTERRUPT_PIN, &irq);
>>         dev->pin = irq;
>>         if (irq)
>>                 pci_read_config_byte(dev, PCI_INTERRUPT_LINE, &irq);
>>         dev->irq = irq;
>>
>>so if the device does not have interrupt pin implemented, pin should be zero.
>>and  pin and irq in dev should
>>be all 0.
>>
>But the device _has_ an interrupt pin implemented.
>The whole point here is that the interrupt line is _NOT_ zero.
>
...
>
>So at one point we have to decide that ->irq is not valid, despite it
>being not set to zero.
>An alternative fix would be this:
>
>diff --git a/drivers/acpi/pci_irq.c b/drivers/acpi/pci_irq.c
>index 68a921d..4a480cb 100644
>--- a/drivers/acpi/pci_irq.c
>+++ b/drivers/acpi/pci_irq.c
>@@ -469,6 +469,7 @@ int acpi_pci_irq_enable(struct pci_dev *dev)
>                } else {
>                        dev_warn(&dev->dev, "PCI INT %c: no GSI\n",
>                                 pin_name(pin));
>+                       dev->irq = 0;
>                }
>                return 0;
>        }
>
>Which probably is a better solution, as here ->irq is _definitely_
>not valid, so we should reset it to '0' to avoid confusion on upper
>layers.
>

Is there any agreement on how to proceed?

-- 
David Härdeman
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