On Saturday 07 January 2012 03:05:40 Mauro Carvalho Chehab wrote:
> On 06-01-2012 22:36, Oliver Endriss wrote:
> > On Wednesday 04 January 2012 20:29:36 Mauro Carvalho Chehab wrote:
> >> drivers/media/dvb/dvb-core/dvb_frontend.c | 541
> >> ++++++++++++++---------------
> >> 1 files changed, 266 insertions(+), 275 deletions(-)
> >> ...
> >> -static int dvb_frontend_check_parameters(struct dvb_frontend *fe,
> >> - struct dvb_frontend_parameters *parms)
> >> +static int dvb_frontend_check_parameters(struct dvb_frontend *fe)
> >> {
> >> ...
> >> - /* check for supported modulation */
> >> - if (fe->ops.info.type == FE_QAM &&
> >> - (parms->u.qam.modulation > QAM_AUTO ||
> >> - !((1 << (parms->u.qam.modulation + 10)) & fe->ops.info.caps))) {
> >> - printk(KERN_WARNING "DVB: adapter %i frontend %i modulation %u
> >> not supported\n",
> >> - fe->dvb->num, fe->id, parms->u.qam.modulation);
> >> + /*
> >> + * check for supported modulation
> >> + *
> >> + * This is currently hacky. Also, it only works for DVB-S & friends,
> >> + * and not all modulations has FE_CAN flags
> >> + */
> >> + switch (c->delivery_system) {
> >> + case SYS_DVBS:
> >> + case SYS_DVBS2:
> >> + case SYS_TURBO:
> >> + if ((c->modulation > QAM_AUTO ||
> >> + !((1 << (c->modulation + 10)) & fe->ops.info.caps))) {
> > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> >> + printk(KERN_WARNING
> >> + "DVB: adapter %i frontend %i modulation %u not
> >> supported\n",
> >> + fe->dvb->num, fe->id, c->modulation);
> >> return -EINVAL;
> >> + }
> >> + break;
> >> ...
> >
> > This code is completely bogus: I get tons of warnings, if vdr tries to
> > tune to DVB-S2 (modulation == 9 == PSK_8) on my stv090x.
> >
> > PSK_8 == 9 is > QAM_AUTO, and the shift operation does not make much
> > sense, except for modulation == 0 == QPSK.
> >
> > The original version makes more sense for me.
>
> Oliver,
>
> At least for DVBv3 calls, the old code will also generate bogus
> warnings if you try to use a DVBv3 call to set PSK_8.
No, since the checks were only performed for type==QAM, i.e. DVB-C.
So DVB-S2 was not affected before.
> I almost removed this validation code during the conversion for several
> reasons:
>
> 1) it does some "magic" by assuming that all QAM modulations are below
> QAM_AUTO;
>
> 2) it checks modulation parameters only for DVB-S. IMO, or the core should
> invalid parameters for all delivery systems, or should let the frontend
> drivers do it;
>
> 3) frontend drivers should already be checking for invalid parameters
> (most of them do it, anyway);
>
> 4) not all modulations are mapped at fe->ops.info.caps, so it is not
> even possible to check for the valid modulations inside the core for
> some delivery systems;
>
> 5) Why the core checks just the modulation, and doesn't check for other
> types of invalid parameters, like FEC and bandwidth?
>
> At the end, I decided to keep it, but added that note, as I really didn't
> like that part of the code.
>
> I can see two fixes for this:
>
> a) just remove the validation, and let the frontend check what's
> supported;
>
> b) rewrite the code with a per-standard table of valid values.
>
> I vote for removing the validation logic there.
Ack.
Atm the core could only do proper checks for frontends, which support a
single delivery system. For multi-delsys frontends some values of the
info struct might not apply to the currently selected delivery system.
To fix this, you need precise information, what is supported for a given
delivery system. In this case we need 'per delivery system' information.
Maybe it would make sense to add a callback, and let the driver do the
checks?
Furthermore, old API-5 applications do not set the delivery system!
For example: VDR checked the FE_CAN_2G_MODULATION flag and eventually
issues a tune call, no matter whether the current delsys is DVB-S or
DVB-S2. So it is difficult to do check parameters in a precise way,
while keeping backward compatibility.
CU
Oliver
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