linux-kernel - Re: [PATCH RESEND][pciutils] libpci: pci_id_lookup

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Message-ID: <CAG-2HqXZvhVDQ-FuM_0EvBysT4UWbfAbfoGdVBPfkjXShgSCfQ@mail.gmail.com>
Date:	Fri, 25 Oct 2013 11:02:15 +0200
From:	Tom Gundersen <teg@...m.no>
To:	Martin Mares <mj@....cz>
Cc:	linux-pci@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RESEND][pciutils] libpci: pci_id_lookup - add udev/hwdb support

On Fri, Sep 13, 2013 at 1:08 PM, Tom Gundersen <teg@...m.no> wrote:
> On Wed, Sep 4, 2013 at 4:59 PM, Tom Gundersen <teg@...m.no> wrote:
>> On Wed, Sep 4, 2013 at 3:57 PM, Martin Mares <mj@....cz> wrote:
>>> Hello!
>>>
>>> First of all: Sorry for not replying to the first mail. I do not follow
>>> linux-pci too much these days (or, I do that in big batches).
>>
>> No problem, I guessed as much.
>>
>>>> This lets you select hwdb support at compile time.
>>>>
>>>> hwdb is an efficient hardware database shipped with recent versions of udev.
>>>> It contains among other sources pci.ids so querying hwdb rather than reading
>>>> pci.ids directly should give the same result.
>>>>
>>>> Ideally Linux distros using udev could stop shipping pci.ids, but use hwdb
>>>> as the only source of this information, which this patch allows.
>>>
>>> Generally, I will be glad to include hwdb support in libpci.
>>
>> Great.
>>
>>>> +     if [ -f /usr/include/libudev.h -o -f /usr/local/include/libudev.h ] ; then
>>>> +             HWDB=yes
>>>> +     else
>>>> +             HWDB=no
>>>> +     fi
>>>
>>> Does this make sense? Does every version of libudev support hwdb?
>>
>> Good point. I'll replace it with a pkg-config call, is that acceptable?
>>
>>>> @@ -86,8 +91,58 @@ char
>>>>  *pci_id_lookup(struct pci_access *a, int flags, int cat, int id1, int id2, int id3, int id4)
>>>>  {
>>>>    struct id_entry *n, *best;
>>>> -  u32 id12 = id_pair(id1, id2);
>>>> -  u32 id34 = id_pair(id3, id4);
>>>> +  u32 id12, id34;
>>>> +
>>>> +#ifdef PCI_HAVE_HWDB
>>>> +  if (!(flags & PCI_LOOKUP_SKIP_LOCAL))
>>>> +    {
>>>
>>> As you wrote it, hwdb has always priority over pci.ids (unless local lookup is
>>> disabled). As a user, I would expect that pci.ids (being a part of the pciutils)
>>> is the primary source of data and other sources (network lookups, hwdb) are
>>> used only if pci.ids do not match or if explicitly requested.
>>
>> Hm, this was actually intentional. The reason being that I'd like to
>> avoid reading in the pci.ids db in the common case, as using the hwdb
>> should be much more efficient (it is most likely already in memory and
>> lookup is constant time), and also we (at the distro level) want to
>> move away from the {usb,pci}.ids and rather default to hwdb
>> everywhere.
>>
>> My original intention was to make hwdb a replacement for pci.ids, but
>> I ended up going the less invasive route, would making it a
>> replacement be more acceptable?
>>
>> If not, I'll just swap around the priority, not a problem.
>
> Hi Martin,
>
> Any comments on the above before I resubmit?

Ping?

-t
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