From: Christoph Hellwig <hch@infradead.org>
To: Alex Williamson <alex.williamson@redhat.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"
<iommu@lists.linux-foundation.org>,
David Woodhouse <dwmw2@infradead.org>
Subject: Re: [PATCH v2 1/3] iommu/uapi: Define uapi version and capabilities
Date: Tue, 14 Apr 2020 01:15:00 -0700 [thread overview]
Message-ID: <20200414081500.GB7315@infradead.org> (raw)
In-Reply-To: <20200413162129.313b3b5a@w520.home>
On Mon, Apr 13, 2020 at 04:21:29PM -0600, Alex Williamson wrote:
> Is the objection to a global version or to any version fields? I don't
> really understand the global version, I'd think a mechanism to check
> extensions plus a per structure flags/version would be preferred. The
> former should resolve how userspace can test support for features
> requiring multiple interfaces. A global version also implies that
> we're only ever adding features and never removing. For example,
> feature Foo is added in version 4, but it's replaced by feature Bar in
> version 5, now userspace can't simply test version >= 4 must include
> feature Foo.
The objection is to versions vs the much more sensible struct size +
capability flags. Making it global just increases the problems with
a version for all of the above reasons.
> It seems to me that version and flags can also be complimentary, for
> example a field might be defined by a version but a flag could indicate
> if it's implemented. With only the flag, we'd infer the field from the
> flag, with only the version we'd need to assume the field is always
> implemented. So I have a hard time making a blanket statement that all
> versions fields should be avoided.
s/version/struct size/, but otherwise agreed.
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next prev parent reply other threads:[~2020-04-14 8:15 UTC|newest]
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
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 [this message]
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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