Re: [PATCH v2] pci: export class IDs from pci_ids.h
From: Bjorn Helgaas
Date: Thu Apr 02 2015 - 18:32:42 EST
On Thu, Apr 2, 2015 at 4:28 PM, Michael S. Tsirkin <mst@xxxxxxxxxx> wrote:
> On Thu, Apr 02, 2015 at 03:53:47PM -0500, Bjorn Helgaas wrote:
>> On Mon, Mar 30, 2015 at 01:33:28PM +0200, Michael S. Tsirkin wrote:
>> > The basic class ID macros in pci_ids.h are pretty useful for userspace
>> > using the pci sysfs interface, and they aren't fundamentally different
>> > from the constants in pci_regs.h - both are defined in the
>> > pci spec.
>> > At the moment userspace is forced to duplicate these macros
>> > (e.g. QEMU does this, so do seabios, gpxe, and others), it is better to
>> > expose them in /usr/include/linux/pci_ids.h so everyone can just include
>> > this header.
>> I agree that it would be nice for applications to get these definitions
>> from a single place, but I'm not sure that include/uapi/linux/pci_ids.h
>> needs to be that place.
>> These constants are just copies of what's in the spec, and I don't think
>> you're suggesting that the constants are necessary to use a kernel API.
>> I know the kernel does provide access to values via sysfs "class" files,
>> but the kernel is just passing the values through from the hardware.
>> That's analogous to reading the class with setpci, and I don't think it
>> leads to a requirement that the kernel export all the information about how
>> to interpret the class values.
>> I haven't looked at libpci or libudev, but it sounds like you think those
>> are not good solutions. Is that because they don't currently have this
>> information? People don't want to add dependencies on them?
> People don't want to add dependencies on them.
Why not? I'm not a user-space programmer, so it's not obvious to me
what the problems with adding a dependency are. If a package provides
functionality you want, it seems like a *good* thing to use it and
depend on it rather than reimplementing the functionality yourself.
The /usr/include/pci/header.h supplied by libpci-dev (on Ubuntu) looks
like it has most or all of the constants you want.
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