[mythtv-commits] Ticket #13443: V4L2 error message for each CaptureCard

[MythTV]

#13443: V4L2 error message for each CaptureCard
-------------------------------------+-------------------------------------
     Reporter:  Klaas de Waal        |      Owner:  Klaas de Waal
         Type:  Patch - Bug Fix      |     Status:  assigned
     Priority:  minor                |  Milestone:  needs_triage
    Component:  MythTV - Mythtv-     |    Version:  Master Head
  setup                              |   Keywords:  V4L2 DVB capturecard
     Severity:  low                  |  setup
Ticket locked:  0                    |
-------------------------------------+-------------------------------------
 After selecting mythtv-setup page "Capture cards" the following error
 message is given in the log for each defined capture card:

 {{{
 2019-04-06 22:26:13.504850 E  V4L2(): Could not open '':
                         eno: No such file or directory (2)

 }}}

 This message is also given when a new capture card is created by selecting
 "(New capture card)".

 What happens is that, when mythtv is configured to support V4L2, each
 instantiation of a CaptureCard object causes a call to
 V4L2encGroup::probeCard. However, at this moment there is no device name
 so this fails.

 The easy fix is to not call probeCard if the device name is empty.\\
 A patch for this is attached.

 However, it maybe possible that there is a more elegant solution.

 The following is a description of what happens in videosource.cpp and
 v4l2util.cpp.\\

 Creation of the CaptureCard:

 {{{
 CaptureCard::CaptureCard(bool use_card_group)
     : m_id(new ID)
 {
     addChild(m_id);
     if (use_card_group)
         CaptureCardGroup(*this);
     addChild(new Hostname(*this));
 }
 }}}

 In CaptureCardGroup::CaptureCardGroup a new V4L2encGroup is created:

 {{{
 #ifdef USING_V4L2
     cardtype->addTargetedChild("V4L2ENC", new V4L2encGroup(parent,
 *cardtype));

 }}}

 In V4L2encGroup::V4L2encGroup then the card probe is called:

 {{{
 probeCard(m_device->getValue());

 }}}
 N.B. The attached patch modifies the above so that probeCard is only
 called when the device name is not empty.

 In V4L2encGroup::probeCard an instance of V4L2util is created:

 {{{
 void V4L2encGroup::probeCard(const QString &device_name)
 {
 #ifdef USING_V4L2
     QString    card_name = tr("Failed to open");
     QString    card_info = card_name;
     V4L2util   v4l2(device_name);

 }}}

 The actual error message this ticket is about is then finally given in
 V4l2util::Open

 {{{
     m_fd = open(dev_name.toLatin1().constData(), O_RDWR);
     if (m_fd < 0)
     {
         LOG(VB_GENERAL, LOG_ERR, LOC +
             QString("Could not open '%1': ").arg(dev_name) + ENO);
         return false;
     }

 }}}

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Ticket URL: <https://code.mythtv.org/trac/ticket/13443>
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