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Re: [PATCH V2 4/5] [Documentation] Media: Update docs for V4L2 FM new features



Hi Manjunatha,

A quick review:

On Wednesday, April 18, 2012 18:06:42 manjunatha_halli@xxxxxx wrote:
> From: Manjunatha Halli <x0130808@xxxxxx>
> 
> The list of new features -
> 	1) New control class for FM RX
> 	2) New FM RX CID's - De-Emphasis filter mode and RDS AF switch
> 	3) New FM TX CID - RDS Alternate frequency set.
> 
> Signed-off-by: Manjunatha Halli <x0130808@xxxxxx>
> ---
>  Documentation/DocBook/media/v4l/compat.xml         |    3 +
>  Documentation/DocBook/media/v4l/controls.xml       |   78 ++++++++++++++++++++
>  Documentation/DocBook/media/v4l/dev-rds.xml        |    5 +-
>  .../DocBook/media/v4l/vidioc-g-ext-ctrls.xml       |    7 ++
>  4 files changed, 91 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/DocBook/media/v4l/compat.xml b/Documentation/DocBook/media/v4l/compat.xml
> index bce97c5..df1f345 100644
> --- a/Documentation/DocBook/media/v4l/compat.xml
> +++ b/Documentation/DocBook/media/v4l/compat.xml
> @@ -2311,6 +2311,9 @@ more information.</para>
>  	  <para>Added FM Modulator (FM TX) Extended Control Class: <constant>V4L2_CTRL_CLASS_FM_TX</constant> and their Control IDs.</para>
>  	</listitem>
>  	<listitem>
> +	<para>Added FM Receiver (FM RX) Extended Control Class: <constant>V4L2_CTRL_CLASS_FM_RX</constant> and their Control IDs.</para>
> +	</listitem>
> +	<listitem>
>  	  <para>Added Remote Controller chapter, describing the default Remote Controller mapping for media devices.</para>
>  	</listitem>
>        </orderedlist>
> diff --git a/Documentation/DocBook/media/v4l/controls.xml b/Documentation/DocBook/media/v4l/controls.xml
> index b84f25e..f6c8034 100644
> --- a/Documentation/DocBook/media/v4l/controls.xml
> +++ b/Documentation/DocBook/media/v4l/controls.xml
> @@ -3018,6 +3018,12 @@ to find receivers which can scroll strings sized as 32 x N or 64 x N characters.
>  with steps of 32 or 64 characters. The result is it must always contain a string with size multiple of 32 or 64. </entry>
>  	  </row>
>  	  <row>
> +	  <entry spanname="id"><constant>V4L2_CID_RDS_TX_AF_FREQ</constant>&nbsp;</entry>
> +	  <entry>integer</entry>
> +	  </row>
> +	  <row><entry spanname="descr">Sets the RDS Alternate Frequency value which allows a receiver to re-tune to a different frequency providing the same station when the first signal becomes too weak (e.g., when moving out of range). </entry>

What is the unit of this frequency? I assume that is defined in the RDS standard?

> +	  </row>
> +	  <row>
>  	    <entry spanname="id"><constant>V4L2_CID_AUDIO_LIMITER_ENABLED</constant>&nbsp;</entry>
>  	    <entry>boolean</entry>
>  	  </row>
> @@ -3146,6 +3152,78 @@ manually or automatically if set to zero. Unit, range and step are driver-specif
>  <xref linkend="en50067" /> document, from CENELEC.</para>
>      </section>
>  
> +    <section id="fm-rx-controls">
> +      <title>FM Receiver Control Reference</title>
> +
> +      <para>The FM Receiver (FM_RX) class includes controls for common features of
> +FM Reception capable devices. Currently this class includes parameter for Alternate
> +frequency.</para>
> +
> +      <table pgwide="1" frame="none" id="fm-rx-control-id">
> +      <title>FM_RX Control IDs</title>
> +
> +      <tgroup cols="4">
> +        <colspec colname="c1" colwidth="1*" />
> +        <colspec colname="c2" colwidth="6*" />
> +        <colspec colname="c3" colwidth="2*" />
> +        <colspec colname="c4" colwidth="6*" />
> +        <spanspec namest="c1" nameend="c2" spanname="id" />
> +        <spanspec namest="c2" nameend="c4" spanname="descr" />
> +        <thead>
> +          <row>
> +            <entry spanname="id" align="left">ID</entry>
> +            <entry align="left">Type</entry>
> +          </row><row rowsep="1"><entry spanname="descr" align="left">Description</entry>
> +          </row>
> +        </thead>
> +        <tbody valign="top">
> +          <row><entry></entry></row>
> +          <row>
> +            <entry spanname="id"><constant>V4L2_CID_FM_RX_CLASS</constant>&nbsp;</entry>
> +            <entry>class</entry>
> +          </row><row><entry spanname="descr">The FM_RX class
> +descriptor. Calling &VIDIOC-QUERYCTRL; for this control will return a
> +description of this control class.</entry>
> +          </row>
> +          <row>
> +            <entry spanname="id"><constant>V4L2_CID_RDS_AF_SWITCH</constant>&nbsp;</entry>
> +            <entry>boolean</entry>
> +          </row>
> +          <row><entry spanname="descr">Enable or Disable's FM RX RDS Alternate frequency feature.</entry>

How does this work? If this is enabled, will the receiver automagically switch to
the alternate frequency if the signal becomes too weak? And how does that affect
VIDIOC_G_FREQUENCY?

> +          </row>
> +          <row>
> +	    <entry spanname="id"><constant>V4L2_CID_TUNE_DEEMPHASIS</constant>&nbsp;</entry>
> +	    <entry>integer</entry>
> +	  </row>
> +	  <row id="v4l2-deemphasis"><entry spanname="descr">Configures the de-emphasis value for reception.
> +A pre-emphasis filter is applied to the broadcast to accentuate the high audio frequencies.
> +Depending on the region, a time constant of either 50 or 75 useconds is used. The enum&nbsp;v4l2_deemphasis
> +defines possible values for pre-emphasis. Here they are:</entry>

Should enum v4l2_preemphasis be reused here? I'm not certain what's best myself.

> +	</row><row>
> +	<entrytbl spanname="descr" cols="2">
> +		  <tbody valign="top">
> +		    <row>
> +		      <entry><constant>V4L2_DEEMPHASIS_DISABLED</constant>&nbsp;</entry>
> +		      <entry>No de-emphasis is applied.</entry>
> +		    </row>
> +		    <row>
> +		      <entry><constant>V4L2_DEEMPHASIS_50_uS</constant>&nbsp;</entry>
> +		      <entry>A de-emphasis of 50 uS is used.</entry>
> +		    </row>
> +		    <row>
> +		      <entry><constant>V4L2_DEEMPHASIS_75_uS</constant>&nbsp;</entry>
> +		      <entry>A de-emphasis of 75 uS is used.</entry>
> +		    </row>
> +		  </tbody>
> +		</entrytbl>
> +
> +	  </row>
> +          <row><entry></entry></row>
> +        </tbody>
> +      </tgroup>
> +      </table>
> +
> +      </section>
>      <section id="flash-controls">
>        <title>Flash Control Reference</title>
>  
> diff --git a/Documentation/DocBook/media/v4l/dev-rds.xml b/Documentation/DocBook/media/v4l/dev-rds.xml
> index 38883a4..8188161 100644
> --- a/Documentation/DocBook/media/v4l/dev-rds.xml
> +++ b/Documentation/DocBook/media/v4l/dev-rds.xml
> @@ -55,8 +55,9 @@ If the driver only passes RDS blocks without interpreting the data
>  the <constant>V4L2_TUNER_CAP_RDS_BLOCK_IO</constant> flag has to be set. If the
>  tuner is capable of handling RDS entities like program identification codes and radio
>  text, the flag <constant>V4L2_TUNER_CAP_RDS_CONTROLS</constant> should be set,
> -see <link linkend="writing-rds-data">Writing RDS data</link> and
> -<link linkend="fm-tx-controls">FM Transmitter Control Reference</link>.</para>
> +see <link linkend="writing-rds-data">Writing RDS data</link>,
> +<link linkend="fm-tx-controls">FM Transmitter Control Reference</link>
> +<link linkend="fm-rx-controls">FM Receiver Control Reference</link>.</para>
>    </section>
>  
>    <section  id="reading-rds-data">
> diff --git a/Documentation/DocBook/media/v4l/vidioc-g-ext-ctrls.xml b/Documentation/DocBook/media/v4l/vidioc-g-ext-ctrls.xml
> index b17a7aa..2a8b44e 100644
> --- a/Documentation/DocBook/media/v4l/vidioc-g-ext-ctrls.xml
> +++ b/Documentation/DocBook/media/v4l/vidioc-g-ext-ctrls.xml
> @@ -258,6 +258,13 @@ These controls are described in <xref
>  These controls are described in <xref
>  		linkend="fm-tx-controls" />.</entry>
>  	  </row>
> +          <row>
> +            <entry><constant>V4L2_CTRL_CLASS_FM_RX</constant></entry>
> +             <entry>0x9c0000</entry>
> +             <entry>The class containing FM Receiver (FM RX) controls.
> +These controls are described in <xref
> +                 linkend="fm-rx-controls" />.</entry>
> +           </row>
>  	  <row>
>  	    <entry><constant>V4L2_CTRL_CLASS_FLASH</constant></entry>
>  	    <entry>0x9c0000</entry>
> 

I'm missing the documentation for the new fm_band field!

Regards,

	Hans
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