linux-kernel - Re: [PATCH rdma-next 2/2] RDMA/mlx5: Implement DMABUF export ops

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Message-ID: <20260120181819.GT961572@ziepe.ca>
Date: Tue, 20 Jan 2026 14:18:19 -0400
From: Jason Gunthorpe <jgg@...pe.ca>
To: Edward Srouji <edwards@...dia.com>
Cc: Leon Romanovsky <leon@...nel.org>,
	Sumit Semwal <sumit.semwal@...aro.org>,
	Christian König <christian.koenig@....com>,
	linux-kernel@...r.kernel.org, linux-rdma@...r.kernel.org,
	linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org,
	linaro-mm-sig@...ts.linaro.org, Yishai Hadas <yishaih@...dia.com>
Subject: Re: [PATCH rdma-next 2/2] RDMA/mlx5: Implement DMABUF export ops

On Thu, Jan 08, 2026 at 01:11:15PM +0200, Edward Srouji wrote:
> +static int phys_addr_to_bar(struct pci_dev *pdev, phys_addr_t pa)
> +{
> +	resource_size_t start, end;
> +	int bar;
> +
> +	for (bar = 0; bar < PCI_STD_NUM_BARS; bar++) {
> +		/* Skip BARs not present or not memory-mapped */
> +		if (!(pci_resource_flags(pdev, bar) & IORESOURCE_MEM))
> +			continue;
> +
> +		start = pci_resource_start(pdev, bar);
> +		end = pci_resource_end(pdev, bar);
> +
> +		if (!start || !end)
> +			continue;
> +
> +		if (pa >= start && pa <= end)
> +			return bar;
> +	}

Don't we know which of the two BARs the mmap entry came from based on
its type? This seems like overkill..

Jason