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Date: Sun, 12 May 2024 10:42:12 -0300
From: Jason Gunthorpe <jgg@nvidia.com>
To: Nicolin Chen <nicolinc@nvidia.com>
Cc: will@kernel.org, robin.murphy@arm.com, kevin.tian@intel.com,
	suravee.suthikulpanit@amd.com, joro@8bytes.org,
	linux-kernel@vger.kernel.org, iommu@lists.linux.dev,
	linux-arm-kernel@lists.infradead.org, linux-tegra@vger.kernel.org,
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	jon.grimm@amd.com, santosh.shukla@amd.com, Dhaval.Giani@amd.com,
	shameerali.kolothum.thodi@huawei.com
Subject: Re: [PATCH RFCv1 03/14] iommufd: Prepare for viommu structures and
 functions
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References: <cover.1712978212.git.nicolinc@nvidia.com>
 <734ef2f4b2b3e743e276d65f775062c5996064f4.1712978212.git.nicolinc@nvidia.com>
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On Fri, Apr 12, 2024 at 08:47:00PM -0700, Nicolin Chen wrote:

> +static inline struct iommufd_object *___iommufd_object_alloc(size_t size)
> +{
> +	struct iommufd_object *obj;
> +
> +	obj = kzalloc(size, GFP_KERNEL_ACCOUNT);
> +	if (!obj)
> +		return ERR_PTR(-ENOMEM);
> +
> +	/* Starts out bias'd by 1 until it is removed from the xarray */
> +	refcount_set(&obj->shortterm_users, 1);
> +	refcount_set(&obj->users, 1);
> +
> +	/*
> +	 * The allocation of an obj->id needs an ictx, so it has to be done
> +	 * after this ___iommufd_object_alloc() callback.
> +	 */
> +
> +	return obj;
> +}

It is probably cleaner to just make the existing allocation work with
a NULL ictx for this case? Then we can use the existing alloc
functions.

> +#define viommu_struct_alloc(name)                                              \
> +	struct iommufd_##name *_iommufd_##name##_alloc(size_t size)            \
> +	{                                                                      \
> +		struct iommufd_object *obj;                                    \
> +		if (WARN_ON(size < sizeof(struct iommufd_##name)))             \
> +			return NULL;                                           \

Then here you'd just use the exisint container_of based flow with the
driver sub struct name passed as the 'obj'

Jason