linux-kernel - Re: [PATCH v3] media: dvb-frontends: add Socionext SC1501A ISDB-S/T demodulator driver

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Date:   Thu, 5 Jul 2018 10:58:42 +0900
From:   "Katsuhiro Suzuki" <suzuki.katsuhiro@...ionext.com>
To:     "'Mauro Carvalho Chehab'" <mchehab+samsung@...nel.org>,
        Suzuki, Katsuhiro/鈴木 勝博 
        <suzuki.katsuhiro@...ionext.com>
Cc:     <linux-media@...r.kernel.org>,
        "Masami Hiramatsu" <masami.hiramatsu@...aro.org>,
        "Jassi Brar" <jaswinder.singh@...aro.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] media: dvb-frontends: add Socionext SC1501A ISDB-S/T demodulator driver

Hi Mauro,

> -----Original Message-----
> From: Mauro Carvalho Chehab <mchehab+samsung@...nel.org>
> Sent: Thursday, July 5, 2018 1:58 AM
> To: Suzuki, Katsuhiro/鈴木 勝博 <suzuki.katsuhiro@...ionext.com>
> Cc: linux-media@...r.kernel.org; Masami Hiramatsu
<masami.hiramatsu@...aro.org>;
> Jassi Brar <jaswinder.singh@...aro.org>; linux-arm-kernel@...ts.infradead.org;
> linux-kernel@...r.kernel.org
> Subject: Re: [PATCH v3] media: dvb-frontends: add Socionext SC1501A ISDB-S/T
> demodulator driver
> 
> Hi Katsuhiro-san,
> 
> Em Thu, 21 Jun 2018 12:17:48 +0900
> Katsuhiro Suzuki <suzuki.katsuhiro@...ionext.com> escreveu:
> 
> > This patch adds a frontend driver for the Socionext SC1501A series
> > and Socionext MN88443x ISDB-S/T demodulators.
> 
> Sorry for taking so long to review it. We're missing a sub-maintainer
> for DVB, with would otherwise speed up reviews of DVB patches.

No problem, thank you for reviewing! I appreciate it.


> >
> > The maximum and minimum frequency of Socionext SC1501A comes from
> > ISDB-S and ISDB-T so frequency range is the following:
> >   - ISDB-S (BS/CS110 IF frequency in kHz, Local freq 10.678GHz)
> >     - Min: BS-1: 1032000 => 1032.23MHz
> >     - Max: ND24: 2701000 => 2070.25MHz
> >   - ISDB-T (in Hz)
> >     - Min: ch13: 470000000 => 470.357857MHz
> >     - Max: ch62: 770000000 => 769.927857MHz
> 
> There is actually an error on that part of the driver. Right now,
> the DVB core expects Satellite frequencies (DVB-S, ISDB-S, ...)
> in kHz. For all other delivery systems, it is in Hz.
> 
> It is this way due to historic reasons. While it won't be hard to
> change the core, that would require to touch all Satellite drivers.
> 
> As there are very few frontend drivers that accept both Satellite
> and Terrestrial standards, what we do, instead, is to setup
> two frontends. See, for example, drivers/media/dvb-frontends/helene.c.
> 

Thank you for describing it. I understand our device is rare case, and 
the reason why Helene has Terrestrial and Satellite structures.

I'm using MN884434 device that has 2 cores. I want to setup DVB adapter 
devices (/dev/dvb/adapter0/*) for our frontend system as the following:

  - adapter0: for core 0, ISDB-T, ISDB-S
  - adapter1: for core 1, ISDB-T, ISDB-S

But it seems one DVB adapter device support only ISDB-T or only ISDB-S 
if I divide structures. So I define the adapters as the following:

  - adapter0: for core 0, ISDB-T
  - adapter1: for core 0, ISDB-S
  - adapter2: for core 1, ISDB-T
  - adapter3: for core 1, ISDB-S

Is this correct?


> ...
> > +static const struct dvb_frontend_ops sc1501a_ops = {
> > +	.delsys = { SYS_ISDBS, SYS_ISDBT },
> > +	.info = {
> > +		.name          = "Socionext SC1501A",
> > +		.frequency_min = 1032000,
> > +		.frequency_max = 770000000,
> > +		.caps = FE_CAN_INVERSION_AUTO | FE_CAN_FEC_AUTO |
> > +			FE_CAN_QAM_AUTO | FE_CAN_TRANSMISSION_MODE_AUTO |
> > +			FE_CAN_GUARD_INTERVAL_AUTO | FE_CAN_HIERARCHY_AUTO,
> > +	},
> > +
> > +	.sleep                   = sc1501a_sleep,
> > +	.set_frontend            = sc1501a_set_frontend,
> > +	.get_tune_settings       = sc1501a_get_tune_settings,
> > +	.read_status             = sc1501a_read_status,
> > +};
> 
> In other words, you'll need to declare two structs here, one for ISDB-T
> and another one for ISDB-S.
> 

OK, I'm going to divide this structure for Terrestrial and Satellite. And
add attach functions same as Helene driver.

I'll send v4 patch.


> Yeah, I know that this sucks. If you are in the mood of touching the
> DVB core, I'm willing to consider a patch that would fix this, provided
> that it won't break backward compatibility with other drivers (or would
> convert the other satellite drivers to use the new way).
> 
> Thanks,
> Mauro

Hmm, I don't know the details of DVB core, I try to investigate it.


Regards,
--
Katsuhiro Suzuki