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    SubjectRe: [RFC] Don't use linux/version.h anymore to indicate a per-driver version - Was: Re: [PATCH 03/37] Remove unneeded version.h includes from include/
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    On Fri, 2011-06-24 at 19:16 -0300, Mauro Carvalho Chehab wrote:
    > Em 24-06-2011 18:04, Andy Walls escreveu:
    > > On Fri, 2011-06-24 at 14:48 -0400, Devin Heitmueller wrote:
    > >> On Fri, Jun 24, 2011 at 2:34 PM, Stefan Richter
    > >> <stefanr@s5r6.in-berlin.de> wrote:
    > >>> If the "driver version" is in fact an ABI version, then the driver author
    > >>> should really increase it only when ABI behavior is changed (and only if
    > >>> the behavior change can only be communicated by version number --- e.g.
    > >>> addition of an ioctl is not among such reasons). And the author should
    > >>> commit behavior changing implementation and version number change in a
    > >>> single changeset.
    > >>>
    > >>> And anybody who backmerges such an ABI behavior change into another kernel
    > >>> branch (stable, longterm, distro...) must backmerge the associated version
    > >>> number change too.
    > >>>
    > >>> Of course sometimes people realize this only after the fact. Or driver
    > >>> authors don't have a clear understanding of ABI versioning to begin with.
    > >>> I am saying so because I had to learn it too; I certainly wasn't born
    > >>> with an instinct knowledge how to do it properly.
    > >>>
    > >>> (Disclaimer: I have no stake in drivers/media/ ABIs. But I am involved
    > >>> in maintaining a userspace ABI elsewhere in drivers/firewire/, and one of
    > >>> the userspace libraries that use this ABI.)
    > >>
    > >> Hi Stefan,
    > >>
    > >> To be clear, I don't think anyone is actually proposing that the
    > >> driver version number really be used as any form of formal "ABI
    > >> versioning" scheme. In almost all cases, it's so the application can
    > >> know to *not* do something is the driver is older than X.
    > >
    > > MythTV, for example, used to use the driver version to work around old
    > > VBI bugs and MPEG encoder quirks that the older version of the driver
    > > may not have known how to handle:
    > >
    > > https://github.com/MythTV/mythtv/blob/b98d3a98e3187000ae652df5ffebe2beb5221ba7/mythtv/libs/libmythtv/mpegrecorder.cpp#L335
    > >
    > > But for newer versions, MythTV could avoid using its own odd hacks.
    > > The bleeding edge MythTV now has most of these removed.
    >
    > Removing it is a good thing.
    >
    > >> Really, this is all about applications being able to jam a hack into
    > >> their code that translates to "don't call this ioctl() with some
    > >> particular argument if it's driver W less than version X, because the
    > >> driver had a bug that is likely to panic the guy's PC".
    > >
    > > Well, not even panics per se, but some thing like the VBI is broken, or
    > > the volume control doesn't work, IR blaster is works for this version,
    > > or something else stupid that is very visible to the end user.
    > >
    > > I also use the driver version for troubleshooting problem with users. I
    > > roughly know what wasn't working in what version of the cx18 and ivtv
    > > drivers. If the end user can tell me the driver version (using v4l2-ctl
    > > --log-status) along with his symptoms, it makes my life easier. Being
    > > able to efficiently help the end user is a win for both me and the end
    > > user.
    >
    > If you add it to MODULE_VERSION, you can get the version with:
    >
    > $ modinfo -F version vivi
    > 0.8.1

    Well, since you mention it....

    http://git.linuxtv.org/media_tree.git?a=blob;f=drivers/media/video/cx18/cx18-driver.c;h=9e2f870f4258665ae6093c762f752d45147a8c98;hb=staging/for_v3.1#l252
    http://git.linuxtv.org/media_tree.git?a=blob;f=drivers/media/video/ivtv/ivtv-driver.c;h=0fb75524484d909af4925c3c33c9f12cf6d6519e;hb=staging/for_v3.1#l280

    However, since I often must ask for the output of v4l2-ctl --log-status,
    which already has the version number, I never need to ask the user to
    run /sbin/modinfo for the version.

    Regards,
    Andy





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