On Mon, 9 Feb 2009, Mauro Carvalho Chehab wrote: > On Thu, 5 Feb 2009 10:57:21 -0800 (PST) > Trent Piepho <xyzzy@xxxxxxxxxxxxx> wrote: > > 01/03: cx88: Fix MPEG kconfig dependencies > > http://linuxtv.org/hg/~tap/v4l-dvb?cmd=changeset;node=2e05fd69e6b6 > > Hmm... This patch converts a depends on into a select. This is not nice, since > select is known to not be properly handled by kernel build system. Also, the > kbuild maintainer recommended us to use select only for options that doesn't > have any dependency. > This is reflected on Kbuild docs: > > Note: select should be used with care. select will force a symbol to a value > without visiting the dependencies. By abusing select you are able to select a > symbol FOO even if FOO depends on BAR that is not set. In general use select I'm aware of the problem with select. One way to deal with is to have whatever is selecting FOO also depend on BAR. In this case CX88_MPEG only has one dependency, VIDEO_CX88. Both CX88_BLACKBIRD and CX88_DVB already depend on VIDEO_CX88 so there is no problem. Since CX88_MPEG is a hidden option and it's highly unlikely it will gain a dependency that CX88_BLACKBIRD and CX88_DVB do not also also have, I think this use of select is not so bad. > So, IMO, we should solve the issue using a different logic that relies only on > depends on. This can be done, it was the other option I mentioned. MPEG needs to be made a visible option, which BLACKBIRD and DVB will then depend on instead of selecting. I didn't do this because of complaints about kernel configuration getting too complex with too many options. So I didn't think a patch exposing another option would be better. It would look something like this: config VIDEO_CX88_MPEG tristate "MPEG and digital TV interface" depends on VIDEO_CX88 help Support for the "MPEG port" on Conexant CX2388x chips, which shows up as function 2 of the PCI device. This is used by DVB/ATSC digital TV cards as well as cards with the Conexant "Blackbird" CX23416 MPEG encoder. config VIDEO_CX88_MPEG tristate "DVB/ATSC Support for cx2388x based TV cards" depends on VIDEO_CX88_MPEG ... config VIDEO_CX88_BLACKBIRD tristate "Blackbird MPEG encoder support (cx2388x + cx23416)" depends on VIDEO_CX88_MPEG ... Would that be better? No select, but there is another option for the user to pick when configuring their cards. -- 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
