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FE_READ_SNR and FE_READ_SIGNAL_STRENGTH docs

DISCUSSION Georgi Chorbadzhiyski 2 participants 5 messages Jan 14, 2014 – Jan 16, 2014

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Documentation Media (V4L/DVB)
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Georgi Chorbadzhiyski

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#0 lore raw

Hi guys, I'm confused the documentation on:

http://linuxtv.org/downloads/v4l-dvb-apis/frontend_fcalls.html#FE_READ_SNR
http://linuxtv.org/downloads/v4l-dvb-apis/frontend_fcalls.html#FE_READ_SIGNAL_STRENGTH

states that these ioctls return int16_t values but frontend.h states:

https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/include/uapi/linux/dvb/frontend.h

#define FE_READ_SIGNAL_STRENGTH _IOR('o', 71, __u16)
#define FE_READ_SNR _IOR('o', 72, __u16)

So which one is true?

Signature · 1 line
Georgi Chorbadzhiyski | http://georgi.unixsol.org/ | http://github.com/gfto/
#1 lore raw

Em Tue, 14 Jan 2014 17:16:10 +0200
Georgi Chorbadzhiyski <[email protected]> escreveu:

Quoted 5 lines

Hi guys, I'm confused the documentation on:

http://linuxtv.org/downloads/v4l-dvb-apis/frontend_fcalls.html#FE_READ_SNR
http://linuxtv.org/downloads/v4l-dvb-apis/frontend_fcalls.html#FE_READ_SIGNAL_STRENGTH

Quoted 8 lines

states that these ioctls return int16_t values but frontend.h states:

https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/include/uapi/linux/dvb/frontend.h

#define FE_READ_SIGNAL_STRENGTH _IOR('o', 71, __u16)
#define FE_READ_SNR _IOR('o', 72, __u16)

So which one is true?

Documentation is wrong. The returned values are unsigned. Would you mind send us a patch fixing it?

Btw, the better is to use the new statistics API, when it is available:
http://linuxtv.org/downloads/v4l-dvb-apis/FE_GET_SET_PROPERTY.html#frontend-stat-properties

As it properly specifies the scale of each value.

If you're working in userspace, the libdvbv5 has functions that use the new API automatically when the DVBv5 statistics are available on a DVB driver, via dvb_fe_retrieve_stats():

http://git.linuxtv.org/v4l-utils.git/blob/HEAD:/lib/include/dvb-fe.h

Signature · 2 lines
Cheers,
Mauro
author
#2 lore raw

Around 01/14/2014 05:30 PM, Mauro Carvalho Chehab scribbled:

Quoted 12 lines

Em Tue, 14 Jan 2014 17:16:10 +0200
Georgi Chorbadzhiyski <[email protected]> escreveu:

Quoted 9 lines

Hi guys, I'm confused the documentation on:

http://linuxtv.org/downloads/v4l-dvb-apis/frontend_fcalls.html#FE_READ_SNR
http://linuxtv.org/downloads/v4l-dvb-apis/frontend_fcalls.html#FE_READ_SIGNAL_STRENGTH

states that these ioctls return int16_t values but frontend.h states:

https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/include/uapi/linux/dvb/frontend.h

Quoted 7 lines
Quoted 4 lines

#define FE_READ_SIGNAL_STRENGTH _IOR('o', 71, __u16)
#define FE_READ_SNR _IOR('o', 72, __u16)

So which one is true?

Documentation is wrong. The returned values are unsigned. Would you mind send us a patch fixing it?

I would be happy to, but I can't find the repo that holds the documentation.

Quoted 5 lines

Btw, the better is to use the new statistics API, when it is available:
http://linuxtv.org/downloads/v4l-dvb-apis/FE_GET_SET_PROPERTY.html#frontend-stat-properties

As it properly specifies the scale of each value.

When it's ready, I'll add support for the API in dvblast.

Signature · 1 line
Georgi Chorbadzhiyski | http://georgi.unixsol.org/ | http://github.com/gfto/
#3 lore raw

Em Tue, 14 Jan 2014 17:55:19 +0200
Georgi Chorbadzhiyski <[email protected]> escreveu:

Quoted 16 lines

Around 01/14/2014 05:30 PM, Mauro Carvalho Chehab scribbled:

Quoted 15 lines

Em Tue, 14 Jan 2014 17:16:10 +0200
Georgi Chorbadzhiyski <[email protected]> escreveu:

Quoted 12 lines

Hi guys, I'm confused the documentation on:

http://linuxtv.org/downloads/v4l-dvb-apis/frontend_fcalls.html#FE_READ_SNR
http://linuxtv.org/downloads/v4l-dvb-apis/frontend_fcalls.html#FE_READ_SIGNAL_STRENGTH

states that these ioctls return int16_t values but frontend.h states:

https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/include/uapi/linux/dvb/frontend.h

#define FE_READ_SIGNAL_STRENGTH _IOR('o', 71, __u16)
#define FE_READ_SNR _IOR('o', 72, __u16)

Quoted 6 lines
Quoted 4 lines
Quoted 1 line

So which one is true?

Documentation is wrong. The returned values are unsigned. Would you mind send us a patch fixing it?

I would be happy to, but I can't find the repo that holds the documentation.

It is in the Kernel tree, under Documentation/DocBook/media/dvb.

Quoted 8 lines
Quoted 6 lines

Btw, the better is to use the new statistics API, when it is available:
http://linuxtv.org/downloads/v4l-dvb-apis/FE_GET_SET_PROPERTY.html#frontend-stat-properties

As it properly specifies the scale of each value.

When it's ready, I'll add support for the API in dvblast.

Good.

Signature · 2 lines
Cheers,
Mauro
author
#4 lore raw

Around 01/14/2014 06:07 PM, Mauro Carvalho Chehab scribbled:

Quoted 18 lines

Em Tue, 14 Jan 2014 17:55:19 +0200
Georgi Chorbadzhiyski <[email protected]> escreveu:

Quoted 16 lines

Around 01/14/2014 05:30 PM, Mauro Carvalho Chehab scribbled:

Quoted 15 lines

Em Tue, 14 Jan 2014 17:16:10 +0200
Georgi Chorbadzhiyski <[email protected]> escreveu:

Quoted 12 lines

Hi guys, I'm confused the documentation on:

http://linuxtv.org/downloads/v4l-dvb-apis/frontend_fcalls.html#FE_READ_SNR
http://linuxtv.org/downloads/v4l-dvb-apis/frontend_fcalls.html#FE_READ_SIGNAL_STRENGTH

states that these ioctls return int16_t values but frontend.h states:

https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/include/uapi/linux/dvb/frontend.h

#define FE_READ_SIGNAL_STRENGTH _IOR('o', 71, __u16)
#define FE_READ_SNR _IOR('o', 72, __u16)

Quoted 8 lines
Quoted 6 lines
Quoted 4 lines
Quoted 1 line

So which one is true?

Documentation is wrong. The returned values are unsigned. Would you mind send us a patch fixing it?

I would be happy to, but I can't find the repo that holds the documentation.

It is in the Kernel tree, under Documentation/DocBook/media/dvb.

The attached file contains the discussed documentation fixes.

Signature · 1 line
Georgi Chorbadzhiyski | http://georgi.unixsol.org/ | http://github.com/gfto/
Quoted 1 line

From 2a633a125e616e8a9e701c34f088d7a4cc020ff8 Mon Sep 17 00:00:00 2001

From: Georgi Chorbadzhiyski <[email protected]>
Date: Thu, 16 Jan 2014 17:04:55 +0200
Subject: [PATCH] doc: Fix FE_READ_SNR and FE_READ_SIGNAL_STRENGTH parameter
types.

The proper types returned from FE_READ_SNR and FE_READ_SIGNAL_STRENGTH are uint16_t not int16_t.

---
 Documentation/DocBook/media/dvb/frontend.xml | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)
Documentation/DocBook/media/dvb/frontend.xml +4 -4
index 0d6e81b..8a6a6ff 100644
@@ -744,7 +744,7 @@ typedef enum fe_hierarchy {
 </para>
 <informaltable><tgroup cols="1"><tbody><row><entry
  align="char">
-<para>int ioctl(int fd, int request = <link linkend="FE_READ_SNR">FE_READ_SNR</link>, int16_t
+<para>int ioctl(int fd, int request = <link linkend="FE_READ_SNR">FE_READ_SNR</link>, uint16_t
  &#x22C6;snr);</para>
 </entry>
  </row></tbody></tgroup></informaltable>

@@ -766,7 +766,7 @@ typedef enum fe_hierarchy {
 </entry>
  </row><row><entry
  align="char">
-<para>int16_t *snr</para>
+<para>uint16_t *snr</para>
 </entry><entry
  align="char">
 <para>The signal-to-noise ratio is stored into *snr.</para>

@@ -791,7 +791,7 @@ typedef enum fe_hierarchy {
 <informaltable><tgroup cols="1"><tbody><row><entry
  align="char">
 <para>int ioctl( int fd, int request =
- <link linkend="FE_READ_SIGNAL_STRENGTH">FE_READ_SIGNAL_STRENGTH</link>, int16_t &#x22C6;strength);</para>
+ <link linkend="FE_READ_SIGNAL_STRENGTH">FE_READ_SIGNAL_STRENGTH</link>, uint16_t &#x22C6;strength);</para>
 </entry>
  </row></tbody></tgroup></informaltable>
 

@@ -814,7 +814,7 @@ typedef enum fe_hierarchy {
 </entry>
  </row><row><entry
  align="char">
-<para>int16_t *strength</para>
+<para>uint16_t *strength</para>
 </entry><entry
  align="char">
 <para>The signal strength value is stored into *strength.</para>
Signature · 1 line
1.8.4