netdev - Re: [RFC] sky2: don't request unused i/o region

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Message-ID: <47B3C650.9040008@pobox.com>
Date:	Wed, 13 Feb 2008 23:40:48 -0500
From:	Jeff Garzik <jgarzik@...ox.com>
To:	Stephen Hemminger <shemminger@...ux-foundation.org>
CC:	netdev@...r.kernel.org
Subject: Re: [RFC] sky2: don't request unused i/o region

Stephen Hemminger wrote:
> The sky2 driver only uses the PCI memory region (0) not the 
> available I/O region.  Some users want to use lots of boards, and the
> I/O space gets exhausted.
> 
> Signed-off-by: Stephen Hemminger <shemminger@...ux-foundation.org>
> 
> --- a/drivers/net/sky2.c	2008-02-13 18:58:21.000000000 -0800
> +++ b/drivers/net/sky2.c	2008-02-13 18:58:55.000000000 -0800
> @@ -4135,9 +4135,9 @@ static int __devinit sky2_probe(struct p
>  		goto err_out;
>  	}
>  
> -	err = pci_request_regions(pdev, DRV_NAME);
> +	err = pci_request_region(pdev, 0, DRV_NAME);
>  	if (err) {
> -		dev_err(&pdev->dev, "cannot obtain PCI resources\n");
> +		dev_err(&pdev->dev, "cannot obtain PCI resource\n");

Your description of the problem does not match the fix.

PCI resources are already allocated to the device (or not) by this point 
in the code.  pci_request_region/regions is purely internal kernel 
software resource reservation -- protecting drivers from themselves, and 
arguably not really needed anymore on modern buses.

Thus, I cannot see how this patch can possibly "exhaust I/O space" -- 
the relevant PCI resources are allocated to the device, or not, 
regardless of these function calls.

As long as there is no resource conflict, you can have 1 million boards 
and still use pci_request_regions().

	Jeff

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