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Subject: Re: [RFC 04/20] iommu: Add iommu_device_get_info interface
To:     David Gibson <david@gibson.dropbear.id.au>,
        Liu Yi L <yi.l.liu@intel.com>
References: <20210919063848.1476776-1-yi.l.liu@intel.com>
 <20210919063848.1476776-5-yi.l.liu@intel.com> <YVPU89utk3JFPzS7@yekko>
 <21cd618b-3ea6-dc89-cc79-e0927dece927@linux.intel.com>
From:   Lu Baolu <baolu.lu@linux.intel.com>
Message-ID: <ba0a7369-c115-2df5-e2bb-bd65ca20a0dc@linux.intel.com>
Date:   Wed, 29 Sep 2021 17:29:17 +0800
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On 2021/9/29 17:25, Lu Baolu wrote:
> Hi David,
> 
> On 2021/9/29 10:52, David Gibson wrote:
>> On Sun, Sep 19, 2021 at 02:38:32PM +0800, Liu Yi L wrote:
>>> From: Lu Baolu<baolu.lu@linux.intel.com>
>>>
>>> This provides an interface for upper layers to get the per-device iommu
>>> attributes.
>>>
>>> ???? int iommu_device_get_info(struct device *dev,
>>> ?????????????????????????????? enum iommu_devattr attr, void *data);
>> That fact that this interface doesn't let you know how to size the
>> data buffer, other than by just knowing the right size for each attr
>> concerns me.
>>
> 
> We plan to address this by following the comments here.
> 
> https://lore.kernel.org/linux-iommu/20210921161930.GP327412@nvidia.com/

And Christoph gave another option as well.

https://lore.kernel.org/linux-iommu/20210922050746.GA12921@lst.de/

Best regards,
baolu