linux-kernel - Re: [PATCH v4 12/23] iommufd/driver: Add iommufd_hw_queue

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Message-ID: <20250515161254.GK382960@nvidia.com>
Date: Thu, 15 May 2025 13:12:54 -0300
From: Jason Gunthorpe <jgg@...dia.com>
To: Nicolin Chen <nicolinc@...dia.com>
Cc: kevin.tian@...el.com, corbet@....net, will@...nel.org,
	bagasdotme@...il.com, robin.murphy@....com, joro@...tes.org,
	thierry.reding@...il.com, vdumpa@...dia.com, jonathanh@...dia.com,
	shuah@...nel.org, jsnitsel@...hat.com, nathan@...nel.org,
	peterz@...radead.org, yi.l.liu@...el.com, mshavit@...gle.com,
	praan@...gle.com, zhangzekun11@...wei.com, iommu@...ts.linux.dev,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-tegra@...r.kernel.org,
	linux-kselftest@...r.kernel.org, patches@...ts.linux.dev,
	mochs@...dia.com, alok.a.tiwari@...cle.com, vasant.hegde@....com
Subject: Re: [PATCH v4 12/23] iommufd/driver: Add
 iommufd_hw_queue_depend/undepend() helpers

On Thu, May 08, 2025 at 08:02:33PM -0700, Nicolin Chen wrote:

> +/*
> + * Helpers for IOMMU driver to build/destroy a dependency between two sibling
> + * structures created by one of the allocators above
> + */
> +#define iommufd_hw_queue_depend(dependent, depended, member)                   \
> +	({                                                                     \
> +		static_assert(__same_type(struct iommufd_hw_queue,             \
> +					  dependent->member));                 \
> +		static_assert(offsetof(typeof(*dependent), member.obj) == 0);  \
> +		static_assert(__same_type(struct iommufd_hw_queue,             \
> +					  depended->member));                  \
> +		static_assert(offsetof(typeof(*depended), member.obj) == 0);   \
> +		_iommufd_object_depend(&dependent->member.obj,                 \
> +				       &depended->member.obj);                 \
> +	})

This doesn't need the offsetof == 0 checks, it isn't an allocator. And
you want to check that the two structs have the same type:

static_assert(__same_type(struct iommufd_hw_queue, dependent->member));
static_assert(__same_type(typeof(*dependent), *dependend));

Jason