linux-kernel - Re: [PATCH v2] PCI: Add DMA alias quirk for PLX PEX NTB

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Date:   Tue, 26 Nov 2019 09:38:33 -0800
From:   Christoph Hellwig <hch@...radead.org>
To:     James Sewart <jamessewart@...sta.com>
Cc:     linux-pci@...r.kernel.org, Dmitry Safonov <0x7f454c46@...il.com>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        Dmitry Safonov <dima@...sta.com>,
        Logan Gunthorpe <logang@...tatee.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Bjorn Helgaas <helgaas@...nel.org>
Subject: Re: [PATCH v2] PCI: Add DMA alias quirk for PLX PEX NTB

> +int _pci_add_dma_alias_range(struct pci_dev *dev, u8 devfn_from, int len)

This should be mrked static.  Also single underscore prefixes are rather
unusual in Linux.  Either use two or use a more descriptive name.


> @@ -5875,18 +5887,21 @@ int pci_set_vga_state(struct pci_dev *dev, bool decode,
>   */
>  void pci_add_dma_alias(struct pci_dev *dev, u8 devfn)
>  {
> -	if (!dev->dma_alias_mask)
> -		dev->dma_alias_mask = bitmap_zalloc(U8_MAX, GFP_KERNEL);
> -	if (!dev->dma_alias_mask) {
> -		pci_warn(dev, "Unable to allocate DMA alias mask\n");
> +	if (_pci_add_dma_alias_range(dev, devfn, 1) != 0)
>  		return;
> -	}
> -
> -	set_bit(devfn, dev->dma_alias_mask);
>  	pci_info(dev, "Enabling fixed DMA alias to %02x.%d\n",
>  		 PCI_SLOT(devfn), PCI_FUNC(devfn));
>  }
>  
> +void pci_add_dma_alias_range(struct pci_dev *dev, u8 devfn_from, int len)
> +{
> +	int devfn_to = devfn_from + len - 1;
> +	if (_pci_add_dma_alias_range(dev, devfn_from, len) != 0)
> +		return;
> +	pci_info(dev, "Enabling fixed DMA alias for devfn range from %02x.%d to %02x.%d\n",
> +		 PCI_SLOT(devfn_from), PCI_FUNC(devfn_from), PCI_SLOT(devfn_to), PCI_FUNC(devfn_to));
> +}

This adds a non-string constant line over 80 chars that should be fixed
up.

But can't you just add the len argument (which really should be
nr_devfns or so) to pci_add_dma_alias and switch the 8 existing
callers over?