On 09/04/2015 01:26 PM, Hans Verkuil wrote:
On 09/01/2015 11:59 PM, Antti Palosaari wrote:
Add SDR specific notes to G_MODULATOR / S_MODULATOR documentation.
Signed-off-by: Antti Palosaari <crope@xxxxxx>
---
Documentation/DocBook/media/v4l/vidioc-g-modulator.xml | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/Documentation/DocBook/media/v4l/vidioc-g-modulator.xml b/Documentation/DocBook/media/v4l/vidioc-g-modulator.xml
index 80167fc..affb694 100644
--- a/Documentation/DocBook/media/v4l/vidioc-g-modulator.xml
+++ b/Documentation/DocBook/media/v4l/vidioc-g-modulator.xml
@@ -78,6 +78,15 @@ different audio modulation if the request cannot be satisfied. However
this is a write-only ioctl, it does not return the actual audio
modulation selected.</para>
+ <para><link linkend="sdr">SDR</link> specific modulator types are
+<constant>V4L2_TUNER_SDR</constant> and <constant>V4L2_TUNER_RF</constant>.
+Valid fields for these modulator types are <structfield>index</structfield>,
+<structfield>name</structfield>, <structfield>capability</structfield>,
+<structfield>rangelow</structfield>, <structfield>rangehigh</structfield>
+and <structfield>type</structfield>. All the rest fields must be
s/rest/remaining/
+initialized to zero by both application and driver.
I would drop this sentence. The spec is clear about which fields have to be set
by the user. The only thing I would mention here is that txsubchans should be
initialized to 0 by applications (we might want to use it in the future) when
calling S_MODULATOR.
For S_TUNER it is the same: only mention that audmode should be initialized to
0 for these SDR tuner types.
+Term modulator means SDR transmitter on this context.</para>
s/Term/The term/
s/on/in/
Note: the same typos are in patch 12/13.
Perhaps this sentence should be rewritten since it is not clear what you
mean. I guess the idea is that 'modulator' is not a good match to what actually
happens in the SDR hardware?
How about:
"Note that the term 'modulator' is a misnomer for type V4L2_TUNER_SDR since
this really is a DAC and the 'modulator' frequency is in reality the sampling
frequency of the DAC."
I hope I got that right.
And do something similar for patch 12/13.
I added it mainly because struct v4l2_modulator is somehow misleading as
it contains both modulator and RF frontend specific stuff and especially
misleading for SDR case as modulator is located in a host computer
software. On DVB side modulator/demodulator and tuner are split more
correctly.
If you look that struct v4l2_modulator:
index: common field
name: common field
capability: contains both RF frontend and modulator stuff
rangelow: RF frontend specific
rangehigh: RF frontend specific
txsubchans: modulator specific
type: common field
reserved: reserved
So actually most field on that struct v4l2_modulator are RF frontend
specific, not modulator. Same applies to struct v4l2_tuner.
These should be probably:
tuner => receiver
modulator => transmitter
Or even better, like DVB side, split modulator/demodulator and RF stuff
to own structs. But as it is not reasonable to start changing those, so
I decided to add comment for tuner that it means SDR receiver and for
modulator it means SDR transmitter.
regards
Antti
+
<para>To change the radio frequency the &VIDIOC-S-FREQUENCY; ioctl
is available.</para>
Regards,
Hans
--
http://palosaari.fi/
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