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@xxxxxxxxxxxxxxxxx> 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 Mauro. -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
