Re: [PATCH RFC 01/91] [media] dvb-core: allow demods to specify the supported delivery systems supported standards.

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On 27.12.2011 14:28, Mauro Carvalho Chehab wrote:
> On 27-12-2011 10:11, Andreas Oberritter wrote:
>> On 27.12.2011 02:07, Mauro Carvalho Chehab wrote:
>>> DVB-S and DVB-T, as those were the standards supported by DVBv3.
>>
>> The description seems to be incomplete.
>>
>>> New standards like DSS, ISDB and CTTB don't fit on any of the
>>> above types.
>>>
>>> while there's a way for the drivers to explicitly change whatever
>>> default DELSYS were filled inside the core, still a fake value is
>>> needed there, and a "compat" code to allow DVBv3 applications to
>>> work with those delivery systems is needed. This is good for a
>>> short term solution, while applications aren't using DVBv5 directly.
>>>
>>> However, at long term, this is bad, as the compat code runs even
>>> if the application is using DVBv5. Also, the compat code is not
>>> perfect, and only works when the frontend is capable of auto-detecting
>>> the parameters that aren't visible by the faked delivery systems.
>>>
>>> So, let the frontend fill the supported delivery systems at the
>>> device properties directly, and, in the future, let the core to use
>>> the delsys to fill the reported info::type based on the delsys.
>>>
>>> Signed-off-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxx>
>>> ---
>>>  drivers/media/dvb/dvb-core/dvb_frontend.c |   13 +++++++++++++
>>>  drivers/media/dvb/dvb-core/dvb_frontend.h |    8 ++++++++
>>>  2 files changed, 21 insertions(+), 0 deletions(-)
>>>
>>> diff --git a/drivers/media/dvb/dvb-core/dvb_frontend.c b/drivers/media/dvb/dvb-core/dvb_frontend.c
>>> index 8dedff4..f17c411 100644
>>> --- a/drivers/media/dvb/dvb-core/dvb_frontend.c
>>> +++ b/drivers/media/dvb/dvb-core/dvb_frontend.c
>>> @@ -1252,6 +1252,19 @@ static void dtv_set_default_delivery_caps(const struct dvb_frontend *fe, struct
>>>  	const struct dvb_frontend_info *info = &fe->ops.info;
>>>  	u32 ncaps = 0;
>>>  
>>> +	/*
>>> +	 * If the frontend explicitly sets a list, use it, instead of
>>> +	 * filling based on the info->type
>>> +	 */
>>> +	if (fe->ops.delsys[ncaps]) {
>>> +		while (fe->ops.delsys[ncaps] && ncaps < MAX_DELSYS) {
>>> +			p->u.buffer.data[ncaps] = fe->ops.delsys[ncaps];
>>> +			ncaps++;
>>> +		}
>>> +		p->u.buffer.len = ncaps;
>>> +		return;
>>> +	}
>>> +
>>
>> I don't understand what this is trying to solve. This is already handled
>> by the get_property driver callback.
>>
>> dtv_set_default_delivery_caps() only sets some defaults for drivers not
>> implementing get_property yet.
> 
> dtv_set_default_delivery_caps() does the wrong thing for delivery systems
> like ISDB-T, ISDB-S, DSS, DMB-TH, as it fills data with a fake value that
> is there at fe->ops.info.type. 
> 
> The fake values there should be used only for DVBv3 legacy calls emulation
> on those delivery systems that are not fully compatible with a DVBv3 call.

That's right. Still, there's no need to introduce fe->ops.delsys,
because the drivers in question could just implement get_property
instead. At least that's what we discussed and AFAIR agreed upon when
Manu recently submitted his patches regarding enumeration of delivery
systems.

> At the end, I think we should deprecate the fe->ops.info.type, as its
> contents is not reliable (as it can represent something else). 
> 
> Btw, there are several places at dvb_frontend.c that uses the info.type
> to assume the delivery system. This leads DVB core to do the wrong assumptions
> for non-DVBv3 supported systems. The right way is to use a new field that
> really represents the supported delivery systems by a given frontend, instead
> of relying on fe->ops.info.type.
> 
> 
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