Add some info what is RF tuner in context of V4L RF tuner class.
Cc: Hans Verkuil <hverkuil@xxxxxxxxx>
Signed-off-by: Antti Palosaari <crope@xxxxxx>
---
Documentation/DocBook/media/v4l/controls.xml | 23 +++++++++++++++++++++--
1 file changed, 21 insertions(+), 2 deletions(-)
diff --git a/Documentation/DocBook/media/v4l/controls.xml b/Documentation/DocBook/media/v4l/controls.xml
index 92e3335..9adf630 100644
--- a/Documentation/DocBook/media/v4l/controls.xml
+++ b/Documentation/DocBook/media/v4l/controls.xml
@@ -4975,8 +4975,27 @@ defines possible values for de-emphasis. Here they are:</entry>
<section id="rf-tuner-controls">
<title>RF Tuner Control Reference</title>
- <para>The RF Tuner (RF_TUNER) class includes controls for common features
-of devices having RF tuner.</para>
+ <para>
+The RF Tuner (RF_TUNER) class includes controls for common features of devices
+having RF tuner.
+ </para>
+ <para>
+In this context, RF tuner is radio receiver circuit between antenna and
+demodulator. It receives radio frequency (RF) from the antenna and converts that
+received signal to lower intermediate frequency (IF) or baseband frequency (BB).
+Tuners that could do baseband output are often called Zero-IF tuners. Older
+tuners were typically simple PLL tuners inside a metal box, whilst newer ones
+are highly integrated chips without a metal box "silicon tuners". These controls
+are mostly applicable for new feature rich silicon tuners, just because older
+tuners does not have much adjustable features.
+ </para>
+ <para>
+For more information about RF tuners see
+<ulink url="http://en.wikipedia.org/wiki/Tuner_%28radio%29";>Tuner (radio)</ulink>
+and
+<ulink url="http://en.wikipedia.org/wiki/RF_front_end";>RF front end</ulink>
+from Wikipedia.
+ </para>
<table pgwide="1" frame="none" id="rf-tuner-control-id">
<title>RF_TUNER Control IDs</title>
--
1.8.5.3
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