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From: Christoph Hellwig <hch@infradead.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>,
	LKML <linux-kernel@vger.kernel.org>,
	iommu@lists.linux-foundation.org,
	Alex Williamson <alex.williamson@redhat.com>,
	David Woodhouse <dwmw2@infradead.org>
Subject: Re: [PATCH v2 1/3] iommu/uapi: Define uapi version and capabilities
Date: Thu, 26 Mar 2020 02:23:16 -0700
Message-ID: <20200326092316.GA31648@infradead.org> (raw)
In-Reply-To: <1585178227-17061-2-git-send-email-jacob.jun.pan@linux.intel.com>

On Wed, Mar 25, 2020 at 04:17:05PM -0700, Jacob Pan wrote:
> Having a single UAPI version to govern the user-kernel data structures
> makes compatibility check straightforward. On the contrary, supporting
> combinations of multiple versions of the data can be a nightmare to
> maintain.
> 
> This patch defines a unified UAPI version to be used for compatibility
> checks between user and kernel.

This is bullshit.  Version numbers don't scale and we've avoided them
everywhere.  You need need flags specifying specific behavior.

> +#define IOMMU_UAPI_VERSION	1
> +static inline int iommu_get_uapi_version(void)
> +{
> +	return IOMMU_UAPI_VERSION;
> +}

Also inline functions like this in UAPI headers that actually get
included by userspace programs simply don't work.
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Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-25 23:17 [PATCH v2 0/3] IOMMU user API enhancement Jacob Pan
2020-03-25 23:17 ` [PATCH v2 1/3] iommu/uapi: Define uapi version and capabilities Jacob Pan
2020-03-26  9:23   ` Christoph Hellwig [this message]
2020-03-26 16:44     ` Jacob Pan
2020-03-27  2:49       ` Tian, Kevin
2020-03-27  7:47         ` Christoph Hellwig
2020-03-27 23:53           ` Jacob Pan
2020-03-30  5:40             ` Tian, Kevin
2020-03-30 16:07               ` Jacob Pan
2020-03-31  6:06                 ` Tian, Kevin
2020-03-31 15:54                   ` Jacob Pan
2020-04-01  5:32                     ` Tian, Kevin
2020-04-02 18:36                       ` Jacob Pan
2020-04-13 20:41                         ` Jacob Pan
2020-04-13 22:21                           ` Alex Williamson
2020-04-14  5:05                             ` Jacob Pan
2020-04-14 16:13                               ` Alex Williamson
2020-04-14 17:13                                 ` Jacob Pan
2020-04-14 22:32                                   ` Jacob Pan
2020-04-14 23:47                                     ` Tian, Kevin
2020-04-15 15:38                                       ` Jacob Pan
2020-04-16  1:27                                         ` Tian, Kevin
2020-04-14  8:15                             ` Christoph Hellwig
2020-04-14  8:11                           ` Christoph Hellwig
2020-04-14 16:06                             ` Jacob Pan
2020-03-25 23:17 ` [PATCH v2 2/3] iommu/uapi: Use unified UAPI version Jacob Pan
2020-03-25 23:17 ` [PATCH v2 3/3] iommu/uapi: Add helper function for size lookup Jacob Pan

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