On Tue, Nov 15, 2005 Andrew de Quincey wrote: > Hi, this patch allows frontends (and the user) to select from one of several > different tuning algorithms. The patch adds four possibilities: > > 1) SW - the current dvb-kernel software zigzag code. > 2) HW - the hardware supports zigzagging internally (e.g. DST), so use that as > it will be faster. > 3) ADAPTIVE - frontend-specific code exploiting frontend-specific features. > 4) SIMPLE - just set the frontend once and do nothing else (e.g. for frequency > scanner apps). > > Frontends can specify which algorithms they support using > FE_CAPS_CAN_TUNE_ALGO_*. They can also specify the default algorithm to use. > Currently the default is SW for all frontends except the DST (which has HW). > > ADAPTIVE is not implemented internally yet. Enough information to do this for > many frontends is provided on their datasheets - for example I know roughly > how to do it for the stv0299, stv0297, and sh1420 frontends. This needs > experimentation before any real adaptive code can be committed to CVS > however, but I thought it was better to change the API _once_ instead of > several times. None of the frontends currently set the > FE_CAN_TUNE_ALGO_ADAPTIVE flag, so it cannot be accidentally enabled. > > The userspace app can also choose an algorithm using an IOCTL. > > When a frontend device is opened read/write, the tuning algo will > automatically be set back to whatever the frontend specified as the default - > so that userspace apps don't have to care if something else changed algos. I wanted to have a way to turn off zig-zag etc. for a long time. However, I would prefer to implement this via an FE_SET_FRONTEND_EXT (bad name, need a better one) ioctl, which is basically the same as FE_SET_FRONTEND plus an added flags field. This way you could have one flag for switching off zig-zag, one for switching band filters for analog tuning (some FE have IF output to feed an analog demod) etc. What do you think? Johannes
