Hello, Am Freitag, 3. April 2009 12:12 schrieb Eduardo Valentin: > On Thu, Apr 02, 2009 at 06:36:37PM +0200, ext Hans Verkuil wrote: > > On Thursday 02 April 2009 14:02:11 Eduardo Valentin wrote: > > > Hi Hans, > > > > > > On Thu, Apr 02, 2009 at 09:47:11AM +0200, ext Hans Verkuil wrote: > > > > On Wednesday 01 April 2009 11:43:28 Eduardo Valentin wrote: > > > > > Hello Mauro and v4l guys, > > > > > > > > > > This series contains a v4l2 radio driver which > > > > > adds support for Silabs si4713 devices. That is > > > > > a FM transmitter device. > > > > > > > > > > As you should know, v4l2 does not contain representation > > > > > of FM Transmitters (at least that I know). So this driver > > > > > was written highly based on FM receivers API, which can > > > > > cover most of basic functionality. However, as expected, > > > > > there are some properties which were not covered. > > > > > For those properties, sysfs nodes were added in order > > > > > to get user interactions. > > > > > > > > > > Comments are wellcome. > > > > > > > > Can you explain in reasonable detail the extra properties needed for > > > > a device like this? You will need to document that anyway :-) Rather > > > > than implementing a private API it would be much more interesting to > > > > turn this into a public V4L2 API that everyone can use. > > > > > > Yes, here is a little description of them: > > > > > > Pilot is an audible tone sent by the device. > > > > > > pilot_frequency - Configures the frequency of the stereo pilot tone. > > > pilot_deviation - Configures pilot tone frequency deviation level. > > > pilot_enabled - Enables or disables the pilot tone feature. > > > > > > The si4713 device is capable of applying audio compression to the > > > transmitted signal. > > > > > > acomp_enabled - Enables or disables the audio dynamic range control > > > feature. acomp_gain - Sets the gain for audio dynamic range control. > > > acomp_threshold - Sets the threshold level for audio dynamic range > > > control. acomp_attack_time - Sets the attack time for audio dynamic > > > range control. acomp_release_time - Sets the release time for audio > > > dynamic range control. > > > > > > Limiter setups audio deviation limiter feature. Once a over deviation > > > occurs, it is possible to adjust the front-end gain of the audio input > > > and always prevent over deviation. > > > > > > limiter_enabled - Enables or disables the limiter feature. > > > limiter_deviation - Configures audio frequency deviation level. > > > limiter_release_time - Sets the limiter release time. > > > > > > power_level - Sets the output power level for signal transmission. > > > > Hmm, there are two ways to implement these: either make a bunch of > > VIDIOC's for each of these categories, or use extended controls to set > > all these values. I'm hardly an expert on FM transmitters, but it all > > seems reasonable to me (i.e., not too specific for this chip). > > > > I am leaning towards extended controls, since that's so easy to extend if > > needed in the future. And I still intend to add sysfs support to controls > > in the future. On the other hand, it's a bit harder to use compared to > > normal VIDIOCs. > > Could you please explain more about extended controls vs. VIDIOC's? > Pointing drivers which uses one of those also would be worth. But yes, > looks like moving this properties to some sort of v4l2 control looks better > implementation. > > > > RDS related > > > > > > rds_enabled - Enables or disables the RDS feature. > > > rds_ps_name - Sets the RDS ps name field for transmission. > > > rds_radio_text - Sets the RDS radio text for transmission. > > > rds_pi - Sets the RDS PI field for transmission. > > > rds_pty - Sets the RDS PTY field for transmission. > > > > So you set the fields and the RDS encoder will just start using them? > > Once you have rds_enabled set, yes, it will transmit them. > > > This too can be done with controls (needs some work, though, to support > > string controls). > > Yes, true. > > > > Region related > > > > > > Setting region will affect other region properties. > > > > > > region_bottom_frequency > > > region_channel_spacing > > > region_preemphasis > > > region_top_frequency > > > > I do not know enough about FM transmissions to judge this. Are these > > region properties something that is regulated by some standards > > commision? Do they also apply when you modulate this over a TV/radio > > cable system? Do you have some documentation or links that I can look at > > to learn more about this? > > > > > stereo_enabled - Enables or disables stereo mode. > > > > > > > How does one pass the audio and rds data to the driver? Note that for > > > > 2.6.31 we will finalize the V4L2 RDS decoder API (I recently posted > > > > an RFC for that, but I haven't had the time to implement the few > > > > changes needed). It would be nice if rds modulator support would be > > > > modeled after this demodulator API if possible. > > > > > > I see. This is good. I think the best way is to have a rds modulator > > > interface. This driver have implemented it as sys properties, as > > > described above. > > > > I don't think there is that much overlap, though. The similarities are > > probably limited to some flags. > > > > > > Does region information really belong in the driver? Perhaps this > > > > should be in a user-space library? (just a suggestion, I'm not sure > > > > at this stage). > > > > > > Ok. Yes, this could be better to implement in user land. However, > > > depending on region that would restrict other properties as well. > > > So, letting user space control that, would allow device operate in > > > wrong intervals for frequencies for instance. > > > > But if you are in region A and you setup the device for region B, then > > it's wrong as well, right? > > > > I also wonder if there are legal requirements that have to be followed > > here? > > Yes, the region thing is somehow bound to limits of specific area rules / > regulation. For instance, Europe frequencies limits are > .bottom_frequency = 8750, > .top_frequency = 10800,
as only an interested reader of this mailinglist maybe i can point you to: http://linuxwireless.org/en/developers/Regulatory. It seems to me it is a similar case and can be used for reference. > BTW, maybe I'm making some confusion, but is there two different APIs for > radios? What is the difference in roles of things that goes into > drivers/media/radio and drivers/media/common/tuners? > > > Regards, > > > > Hans > > > > -- > > Hans Verkuil - video4linux developer - sponsored by TANDBERG -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
