Linux IOMMU Development
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From: Jean-Philippe Brucker <jean-philippe@linaro.org>
To: Jacob Pan <jacob.jun.pan@linux.intel.com>
Cc: "Tian, Kevin" <kevin.tian@intel.com>,
	Raj Ashok <ashok.raj@intel.com>,
	Jean-Philippe Brucker <jean-philippe@linaro.com>,
	iommu@lists.linux-foundation.org,
	LKML <linux-kernel@vger.kernel.org>,
	Alex Williamson <alex.williamson@redhat.com>,
	David Woodhouse <dwmw2@infradead.org>,
	Jonathan Cameron <jic23@kernel.org>
Subject: Re: [PATCH 3/3] iommu/uapi: Add helper function for size lookup
Date: Fri, 7 Feb 2020 09:47:32 +0100	[thread overview]
Message-ID: <20200207084732.GA1994440@myrica> (raw)
In-Reply-To: <20200203144102.643f9684@jacob-builder>

On Mon, Feb 03, 2020 at 02:41:02PM -0800, Jacob Pan wrote:
> Yeah, that would work as well. I just feel IOMMU UAPI is unlikely to get
> updated frequently, should be much less than adding new capabilities.
> I think argsz could be viewed as the version field set by the
> user, minsz is what kernel current code supports.
> 
> So let me summarize the options we have
> 1. Disallow adding new members to each structure other than reuse
> padding bits or adding union members at the end.
> 2. Allow extension of the structures beyond union, but union size has
> to be fixed with reserved spaces
> 3. Adopt VFIO argsz scheme, I don't think we need version for each
> struct anymore. argsz implies the version that user is using assuming
> UAPI data is extension only.
> 
> Jean, Eric, any comments? My preference is #1. In the apocalyptic event
> when we run out of padding, perhaps we can introduce a new API_v2 :)

I agree, new extensions will most likely want to extend the vendor
specific structures at the end rather than introduce new common fields, so
I prefer #1 which avoids fixing the union size.

Thanks,
Jean
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  parent reply	other threads:[~2020-02-07  8:47 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-29  6:02 [PATCH 0/3] IOMMU user API enhancement Jacob Pan
2020-01-29  6:02 ` [PATCH 1/3] iommu/uapi: Define uapi version and capabilities Jacob Pan
2020-02-06 10:14   ` Auger Eric
2020-02-06 18:22     ` Jacob Pan
2020-01-29  6:02 ` [PATCH 2/3] iommu/uapi: Use unified UAPI version Jacob Pan
2020-01-29  6:02 ` [PATCH 3/3] iommu/uapi: Add helper function for size lookup Jacob Pan
2020-01-29 21:40   ` Alex Williamson
2020-01-29 22:19     ` Alex Williamson
2020-01-31 19:51       ` Jacob Pan
2020-01-31 23:51       ` Jacob Pan
2020-02-03 18:27         ` Alex Williamson
2020-02-03 20:41           ` Jacob Pan
2020-02-03 21:12             ` Alex Williamson
2020-02-03 22:41               ` Jacob Pan
2020-02-06 10:14                 ` Auger Eric
2020-02-07  8:47                 ` Jean-Philippe Brucker [this message]
2020-01-31 17:56     ` Jacob Pan

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