Support for Si468x radio receiver

Support for Si468x radio receiver

[Robert Tiemann]

Hi!

We'd like to use the Silicon Labs Si4688 FM/HD/DAB/DAB+ radio receiver
chip in a product, but there is no kernel support for it yet. We have
the full datasheet and Si468x Programming Guide available, so it
should be possible to write a driver for that chip. The kernel
supports the Si4768 already (which can do AM/FM/HD radio, but not
DAB/DAB+), so I figured it should not be to hard to get the Si4688
supported...

Then I checked the kernel sources for how DAB+ radio tuners are
supposed to be handled by V4L2, but found nothing. Seems like V4L2 is
restricted to abstraction of analog radio tuners, and there is
currently no way to support DAB+ receivers. Is this correct or did I
miss something? The same seems to be true about FM HD (the
radio-si476x driver doesn't seem to support FM HD, only AM and FM).

Now, my question is, how should the FM HD/DAB/DAB+ parts of a
hypothetical radio-si468x driver be implemented? Since DAB is quite
different from FM, do we need a new tuner type in addition to
V4L2_TUNER_RADIO? Or just new V4L2_BAND_MODULATION_FM_HD and
V4L2_BAND_MODULATION_DAB definitions? Or is V4L2 sufficient the way
it is and I am simply failing to understand how it should work?

Best regards,
Robert

Re: Support for Si468x radio receiver

[Hans Verkuil]

Hi Robert,

On 10/1/24 15:35, Robert Tiemann wrote:
> Hi!
> 
> We'd like to use the Silicon Labs Si4688 FM/HD/DAB/DAB+ radio receiver
> chip in a product, but there is no kernel support for it yet. We have
> the full datasheet and Si468x Programming Guide available, so it
> should be possible to write a driver for that chip. The kernel
> supports the Si4768 already (which can do AM/FM/HD radio, but not
> DAB/DAB+), so I figured it should not be to hard to get the Si4688
> supported...
> 
> Then I checked the kernel sources for how DAB+ radio tuners are
> supposed to be handled by V4L2, but found nothing. Seems like V4L2 is
> restricted to abstraction of analog radio tuners, and there is
> currently no way to support DAB+ receivers. Is this correct or did I
> miss something? The same seems to be true about FM HD (the
> radio-si476x driver doesn't seem to support FM HD, only AM and FM).
> 
> Now, my question is, how should the FM HD/DAB/DAB+ parts of a
> hypothetical radio-si468x driver be implemented? Since DAB is quite
> different from FM, do we need a new tuner type in addition to
> V4L2_TUNER_RADIO? Or just new V4L2_BAND_MODULATION_FM_HD and
> V4L2_BAND_MODULATION_DAB definitions? Or is V4L2 sufficient the way
> it is and I am simply failing to understand how it should work?

First of all, I don't think we have any drivers that support DAB(+) today
in the mainline kernel. My limited understanding of DAB is that it is actually
something you would implement as part of the DVB API (digital video broadcasting).

I see a SYS_DAB in include/uapi/linux/dvb/frontend.h, suggesting that it is
indeed something that should be part of dvb, but that's where my knowledge
ends.

I CCed Mauro, he is the DVB expert, and he might know more about this.

Regards,

	Hans

Re: Support for Si468x radio receiver

[Mauro Carvalho Chehab]

Em Wed, 2 Oct 2024 11:21:57 +0200
Hans Verkuil <hverkuil@xs4all.nl> escreveu:

> Hi Robert,
> 
> On 10/1/24 15:35, Robert Tiemann wrote:
> > Hi!
> > 
> > We'd like to use the Silicon Labs Si4688 FM/HD/DAB/DAB+ radio receiver
> > chip in a product, but there is no kernel support for it yet. We have
> > the full datasheet and Si468x Programming Guide available, so it
> > should be possible to write a driver for that chip. The kernel
> > supports the Si4768 already (which can do AM/FM/HD radio, but not
> > DAB/DAB+), so I figured it should not be to hard to get the Si4688
> > supported...
> > 
> > Then I checked the kernel sources for how DAB+ radio tuners are
> > supposed to be handled by V4L2, but found nothing. Seems like V4L2 is
> > restricted to abstraction of analog radio tuners, and there is
> > currently no way to support DAB+ receivers. Is this correct or did I
> > miss something? The same seems to be true about FM HD (the
> > radio-si476x driver doesn't seem to support FM HD, only AM and FM).
> > 
> > Now, my question is, how should the FM HD/DAB/DAB+ parts of a
> > hypothetical radio-si468x driver be implemented? Since DAB is quite
> > different from FM, do we need a new tuner type in addition to
> > V4L2_TUNER_RADIO? Or just new V4L2_BAND_MODULATION_FM_HD and
> > V4L2_BAND_MODULATION_DAB definitions? Or is V4L2 sufficient the way
> > it is and I am simply failing to understand how it should work?  
> 
> First of all, I don't think we have any drivers that support DAB(+) today
> in the mainline kernel. My limited understanding of DAB is that it is actually
> something you would implement as part of the DVB API (digital video broadcasting).
> 
> I see a SYS_DAB in include/uapi/linux/dvb/frontend.h, suggesting that it is
> indeed something that should be part of dvb, but that's where my knowledge
> ends.
> 
> I CCed Mauro, he is the DVB expert, and he might know more about this.

Yeah, the best is to implement DAB support using DVB API. There are some
media drivers that support both V4L2 and DVB API, but, as we don't have
currently any driver using SYS_DAB, we'll probably need to add some
properties to handle it at the DVB frontend API.
> 
> Regards,
> 
> 	Hans



Thanks,
Mauro

Re: Support for Si468x radio receiver

[Robert Tiemann]

Hi!

On 10/2/24 11:53 AM, Mauro Carvalho Chehab wrote:

> Yeah, the best is to implement DAB support using DVB API. There are some
> media drivers that support both V4L2 and DVB API, but, as we don't have
> currently any driver using SYS_DAB, we'll probably need to add some
> properties to handle it at the DVB frontend API.

Seems like someone has to take the first step, I guess. I'll dive a bit
into the API to see how it works.

Many thanks to you both!

> Thanks,
> Mauro

Cheers,
Robert