linux-kernel - Re: [PATCH] uio: add irq control support to uio_pci

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Date:	Thu, 16 Apr 2015 09:43:24 +0200
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Stephen Hemminger <stephen@...workplumber.org>
Cc:	"Hans J. Koch" <hjk@...sjkoch.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] uio: add irq control support to uio_pci_generic

On Wed, Apr 15, 2015 at 09:59:34AM -0700, Stephen Hemminger wrote:
> The driver already supported INTX interrupts but had no in kernel
> function to enable and disable them.
> 
> It is possible for userspace to do this by accessing PCI config
> directly, but this racy

How is it racy? We have userspace using this interface,
if there's a race I want to fix it.

> and better handled by same mechanism
> that already exists in kernel.
> 
> Signed-off-by: Stephen Hemminger <stephen@...workplumber.org>
> 
> 
> --- a/drivers/uio/uio_pci_generic.c	2015-04-15 08:50:15.543900681 -0700
> +++ b/drivers/uio/uio_pci_generic.c	2015-04-15 09:00:01.658609786 -0700
> @@ -53,6 +53,18 @@ static irqreturn_t irqhandler(int irq, s
>  	return IRQ_HANDLED;
>  }
>  
> +static int irqcontrol(struct uio_info *info, s32 irq_on)
> +{
> +	struct uio_pci_generic_dev *gdev = to_uio_pci_generic_dev(info);
> +	struct pci_dev *pdev = gdev->pdev;
> +
> +	pci_cfg_access_lock(pdev);
> +	pci_intx(pdev, irq_on);
> +	pci_cfg_access_unlock(pdev);
> +
> +	return 0;
> +}
> +
>  static int probe(struct pci_dev *pdev,
>  			   const struct pci_device_id *id)
>  {
> @@ -89,6 +101,7 @@ static int probe(struct pci_dev *pdev,
>  	gdev->info.irq = pdev->irq;
>  	gdev->info.irq_flags = IRQF_SHARED;
>  	gdev->info.handler = irqhandler;
> +	gdev->info.irqcontrol = irqcontrol;
>  	gdev->pdev = pdev;
>  
>  	err = uio_register_device(&pdev->dev, &gdev->info);
--
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