linux-kernel - Re: [PATCH 00/86] pci: export pci

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Message-ID: <1427980645.4281.78.camel@chaos.site>
Date:	Thu, 02 Apr 2015 15:17:25 +0200
From:	Jean Delvare <jdelvare@...e.de>
To:	"Michael S. Tsirkin" <mst@...hat.com>
Cc:	Christoph Hellwig <hch@...radead.org>,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Dave Jones <davej@...hat.com>,
	Jesse Barnes <jbarnes@...tuousgeek.org>
Subject: Re: [PATCH 00/86] pci: export pci_ids.h and related cleanups

Le Thursday 02 April 2015 à 14:05 +0200, Michael S. Tsirkin a écrit :
> On Thu, Apr 02, 2015 at 01:15:30PM +0200, Jean Delvare wrote:
> > Le Thursday 02 April 2015 à 12:09 +0200, Michael S. Tsirkin a écrit :
> > > On Thu, Apr 02, 2015 at 11:04:16AM +0200, Jean Delvare wrote:
> > > > Le Thursday 02 April 2015 à 01:23 -0700, Christoph Hellwig a écrit :
> > > > > The class ids are a hardware defintion, not a kernel API.  Just use the
> > > > > definitions from libpci, or copy over the kernel header if you prefer
> > > > > it over the libpci definutions.
> > > > 
> > > > I agree with Christoph, such defines would better come from
> > > > pciutils-devel, not the kernel.
> > > 
> > > This just leads to code duplication.  Projects that don't link with
> > > pciutils don't want to depend on it.
> > 
> > Well, they don't have to depend on anything then, they can keep defining
> > their own named IDs.
> > 
> > Please realize that 1* code duplication is impossible to avoid
> > completely and 2* this hardly qualifies as code duplication in the first
> > place (giving symbolic names to constants is not actual programming.)
> 
> If it's not actual programming, why keep arguing about it?

Clam down, please. You brought it on the table, not me. I'm only trying
to help.

>  What's the problem with exporting class IDs?  Zero maintainance overhead and makes
> life a bit easier to userspace.

Anything that belongs to uapi implies maintenance overhead: greater care
to what is being added, and impossibility to rename or remove anything.
Plus, as explained before, this is conceptually wrong, these values are
defined externally and are not a kernel API.

You still have not explained how user-space would actually benefit from
the change anyway, as previous kernels did not export that file,
projects can't rely on it unless they stop supporting all kernels before
v4.1.

And again, just because exporting this file (or even part of it) looks
convenient, doesn't mean it's right. I am under the impression that you
did not read my previous explanations very carefully. That's sad because
they took me a long time to write.

-- 
Jean Delvare
SUSE L3 Support

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