linux-kernel - Re: [PATCH 6/8] iommu: Retire bus ops

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Message-ID: <d798bc7b-a87a-26b2-17e0-48e9c7715abc@linux.intel.com>
Date:   Fri, 20 Jan 2023 08:27:08 +0800
From:   Baolu Lu <baolu.lu@...ux.intel.com>
To:     Robin Murphy <robin.murphy@....com>, joro@...tes.org,
        will@...nel.org
Cc:     baolu.lu@...ux.intel.com, hch@....de, jgg@...dia.com,
        iommu@...ts.linux.dev, linux-kernel@...r.kernel.org,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH 6/8] iommu: Retire bus ops

On 2023/1/20 3:18, Robin Murphy wrote:
> +	/*
> +	 * For FDT-based systems and ACPI IORT/VIOT, drivers register IOMMU
> +	 * instances with non-NULL fwnodes, and client devices should have been
> +	 * identified with a fwspec by this point. For Intel/AMD/s390/PAMU we
> +	 * can assume a single active driver with global ops, and so grab those
> +	 * from any registered instance, cheekily co-opting the same mechanism.
> +	 */
> +	fwspec = dev_iommu_fwspec_get(dev);
> +	if (fwspec && fwspec->ops)
> +		ops = fwspec->ops;
> +	else
> +		ops = iommu_ops_from_fwnode(NULL);

I'm imagining if Intel/AMD/s390 drivers need to give up global ops.
Is there any way to allow them to make such conversion? I am just
thinking about whether this is a hard limitation for these drivers.

Best regards,
baolu