From: Christoph Hellwig <hch@infradead.org> To: Alex Williamson <alex.williamson@redhat.com> Cc: Jacob Pan <jacob.jun.pan@linux.intel.com>, "Tian, Kevin" <kevin.tian@intel.com>, Christoph Hellwig <hch@infradead.org>, Joerg Roedel <joro@8bytes.org>, Lu Baolu <baolu.lu@linux.intel.com>, "iommu@lists.linux-foundation.org" <iommu@lists.linux-foundation.org>, LKML <linux-kernel@vger.kernel.org>, David Woodhouse <dwmw2@infradead.org>, Jean-Philippe Brucker <jean-philippe@linaro.com>, "Raj, Ashok" <ashok.raj@intel.com> 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.
WARNING: multiple messages have this Message-ID (diff)
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. _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
next prev parent reply other threads:[~2020-04-14 8:15 UTC|newest] Thread overview: 54+ 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 ` Jacob Pan 2020-03-25 23:17 ` [PATCH v2 1/3] iommu/uapi: Define uapi version and capabilities Jacob Pan 2020-03-25 23:17 ` Jacob Pan 2020-03-26 9:23 ` Christoph Hellwig 2020-03-26 9:23 ` Christoph Hellwig 2020-03-26 16:44 ` Jacob Pan 2020-03-26 16:44 ` Jacob Pan 2020-03-27 2:49 ` Tian, Kevin 2020-03-27 2:49 ` Tian, Kevin 2020-03-27 7:47 ` Christoph Hellwig 2020-03-27 7:47 ` Christoph Hellwig 2020-03-27 23:53 ` Jacob Pan 2020-03-27 23:53 ` Jacob Pan 2020-03-30 5:40 ` Tian, Kevin 2020-03-30 5:40 ` Tian, Kevin 2020-03-30 16:07 ` Jacob Pan 2020-03-30 16:07 ` Jacob Pan 2020-03-31 6:06 ` Tian, Kevin 2020-03-31 6:06 ` Tian, Kevin 2020-03-31 15:54 ` Jacob Pan 2020-03-31 15:54 ` Jacob Pan 2020-04-01 5:32 ` Tian, Kevin 2020-04-01 5:32 ` Tian, Kevin 2020-04-02 18:36 ` Jacob Pan 2020-04-02 18:36 ` Jacob Pan 2020-04-13 20:41 ` Jacob Pan 2020-04-13 20:41 ` Jacob Pan 2020-04-13 22:21 ` Alex Williamson 2020-04-13 22:21 ` Alex Williamson 2020-04-14 5:05 ` Jacob Pan 2020-04-14 5:05 ` Jacob Pan 2020-04-14 16:13 ` Alex Williamson 2020-04-14 16:13 ` Alex Williamson 2020-04-14 17:13 ` Jacob Pan 2020-04-14 17:13 ` Jacob Pan 2020-04-14 22:32 ` Jacob Pan 2020-04-14 22:32 ` Jacob Pan 2020-04-14 23:47 ` Tian, Kevin 2020-04-14 23:47 ` Tian, Kevin 2020-04-15 15:38 ` Jacob Pan 2020-04-15 15:38 ` Jacob Pan 2020-04-16 1:27 ` Tian, Kevin 2020-04-16 1:27 ` Tian, Kevin 2020-04-14 8:15 ` Christoph Hellwig [this message] 2020-04-14 8:15 ` Christoph Hellwig 2020-04-14 8:11 ` Christoph Hellwig 2020-04-14 8:11 ` Christoph Hellwig 2020-04-14 16:06 ` Jacob Pan 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 ` Jacob Pan 2020-03-25 23:17 ` [PATCH v2 3/3] iommu/uapi: Add helper function for size lookup Jacob Pan 2020-03-25 23:17 ` Jacob Pan
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