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[media] V4L2 spec: clarify a few modulator issues 

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
This commit is contained in:
Hans Verkuil 2012-05-28 07:42:54 -03:00 committed by Mauro Carvalho Chehab
parent 54f6019b58
commit efcf5bdac8
1 changed files with 13 additions and 4 deletions
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17
Documentation/DocBook/media/v4l/common.xml
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@ -464,14 +464,14 @@ The <structfield>type</structfield> field of the respective
<structfield>tuner</structfield> field contains the index number of
the tuner.</para>
<para>Radio devices have exactly one tuner with index zero, no
<para>Radio input devices have exactly one tuner with index zero, no
video inputs.</para>
<para>To query and change tuner properties applications use the
&VIDIOC-G-TUNER; and &VIDIOC-S-TUNER; ioctl, respectively. The
&v4l2-tuner; returned by <constant>VIDIOC_G_TUNER</constant> also
contains signal status information applicable when the tuner of the
current video input, or a radio tuner is queried. Note that
current video or radio input is queried. Note that
<constant>VIDIOC_S_TUNER</constant> does not switch the current tuner,
when there is more than one at all. The tuner is solely determined by
the current video input. Drivers must support both ioctls and set the
@ -491,8 +491,17 @@ the modulator. The <structfield>type</structfield> field of the
respective &v4l2-output; returned by the &VIDIOC-ENUMOUTPUT; ioctl is
set to <constant>V4L2_OUTPUT_TYPE_MODULATOR</constant> and its
<structfield>modulator</structfield> field contains the index number
of the modulator. This specification does not define radio output
devices.</para>
of the modulator.</para>
<para>Radio output devices have exactly one modulator with index
zero, no video outputs.</para>
<para>A video or radio device cannot support both a tuner and a
modulator. Two separate device nodes will have to be used for such
hardware, one that supports the tuner functionality and one that supports
the modulator functionality. The reason is a limitation with the
&VIDIOC-S-FREQUENCY; ioctl where you cannot specify whether the frequency
is for a tuner or a modulator.</para>
<para>To query and change modulator properties applications use
the &VIDIOC-G-MODULATOR; and &VIDIOC-S-MODULATOR; ioctl. Note that