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Reading devices under /dev/.

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  • J jigarp

    @jsulm
    This link provides information for linux drivers
    https://www.kernel.org/doc/Documentation/rpmsg.txt

    This will provide interface for Ti processors
    http://processors.wiki.ti.com/index.php/PRU-ICSS_Remoteproc_and_RPMsg
    http://processors.wiki.ti.com/index.php/PRU-ICSS_Rpmsg_Driver

    It is a kind of charcter device.
    I'm able to write it using QFile
    don't know how to read.

    Sample for linux userspace commands

    echo Hello > /dev/rpmsg*
    cat /dev/rpmsg*
    C^
    

    Can you provide details for how to read and write Character Device.

    Thank you

    jsulmJ Offline
    jsulmJ Offline
    jsulm
    Lifetime Qt Champion
    wrote on last edited by
    #6

    @jigarp You read like any other file

    https://forum.qt.io/topic/113070/qt-code-of-conduct

    1 Reply Last reply
    1
    • J Offline
      J Offline
      jigarp
      wrote on last edited by
      #7

      In this way i'm trying to write data to rpmsg

      QFile armIpcWriteMsg("/dev/rpmsg_pru30");
      QTextStream outstream(&armIpcWriteMsg);
      qDebug() << "Writing PRU Data";
      if(armIpcWriteMsg.open(QIODevice::WriteOnly))
      {
          outstream << "Hello";
      armIpcWriteMsg.close();
      }
      

      In this way i'm trying to read.

      QFile armIpcReadMsg("/dev/rpmsg_pru30");
      if(armIpcReadMsg.exists())
      {
          if(armIpcReadMsg.open(QIODevice::ReadOnly | QIODevice::Unbuffered))
          {
              char buff[20];
      
              armIpcReadMsg.read(buff,1);
              qDebug() << "PRU2ARM:" << buff;
              armIpcReadMsg.close();
          }
      }
      

      Is it the right way?

      jsulmJ 1 Reply Last reply
      0
      • J jigarp

        In this way i'm trying to write data to rpmsg

        QFile armIpcWriteMsg("/dev/rpmsg_pru30");
        QTextStream outstream(&armIpcWriteMsg);
        qDebug() << "Writing PRU Data";
        if(armIpcWriteMsg.open(QIODevice::WriteOnly))
        {
            outstream << "Hello";
        armIpcWriteMsg.close();
        }
        

        In this way i'm trying to read.

        QFile armIpcReadMsg("/dev/rpmsg_pru30");
        if(armIpcReadMsg.exists())
        {
            if(armIpcReadMsg.open(QIODevice::ReadOnly | QIODevice::Unbuffered))
            {
                char buff[20];
        
                armIpcReadMsg.read(buff,1);
                qDebug() << "PRU2ARM:" << buff;
                armIpcReadMsg.close();
            }
        }
        

        Is it the right way?

        jsulmJ Offline
        jsulmJ Offline
        jsulm
        Lifetime Qt Champion
        wrote on last edited by
        #8

        @jigarp Should be OK. Did you try it out?

        https://forum.qt.io/topic/113070/qt-code-of-conduct

        1 Reply Last reply
        0
        • J Offline
          J Offline
          jigarp
          wrote on last edited by
          #9

          I've tried it.
          I'm able to write successfully.

          But while trying to read file it waits until data became available.
          I wan't to check for data availability before reading that file.

          I've tried QFileinfo by monitoring its size but it is always zero.
          Is there any way to check for ready read.

          jsulmJ 1 Reply Last reply
          0
          • J jigarp

            I've tried it.
            I'm able to write successfully.

            But while trying to read file it waits until data became available.
            I wan't to check for data availability before reading that file.

            I've tried QFileinfo by monitoring its size but it is always zero.
            Is there any way to check for ready read.

            jsulmJ Offline
            jsulmJ Offline
            jsulm
            Lifetime Qt Champion
            wrote on last edited by
            #10

            @jigarp I don't think there is anything in Qt for that.
            I see two possibilities:

            1. Use a second thread where you call read()
            2. Use C API call select() (see man select)

            https://forum.qt.io/topic/113070/qt-code-of-conduct

            1 Reply Last reply
            0
            • Cleiton BuenoC Offline
              Cleiton BuenoC Offline
              Cleiton Bueno
              wrote on last edited by
              #11

              I agree!

              Create a separate thread to handle the device, use (select () or poll ()) and signals to notify other classes or get to the GUI.

              J 1 Reply Last reply
              1
              • SGaistS Offline
                SGaistS Offline
                SGaist
                Lifetime Qt Champion
                wrote on last edited by
                #12

                Hi,

                QFileSystemWatcher might be of interest.

                Interested in AI ? www.idiap.ch
                Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

                1 Reply Last reply
                2
                • Cleiton BuenoC Cleiton Bueno

                  I agree!

                  Create a separate thread to handle the device, use (select () or poll ()) and signals to notify other classes or get to the GUI.

                  J Offline
                  J Offline
                  jigarp
                  wrote on last edited by jigarp
                  #13

                  @Cleiton-Bueno @jsulm
                  In my case i'm reading this file in a thread but there are some more work involved so it is necessory to check whether data available or not.I can not wait until data available.
                  Is there any way to check data available like size or any other.
                  File.size() always responds with 0

                  Create a separate thread to handle the device, use (select () or poll ()) and signals to notify other classes or get to the GUI.
                  

                  How to use Can you provide any samples???

                  jsulmJ 1 Reply Last reply
                  0
                  • J jigarp

                    @Cleiton-Bueno @jsulm
                    In my case i'm reading this file in a thread but there are some more work involved so it is necessory to check whether data available or not.I can not wait until data available.
                    Is there any way to check data available like size or any other.
                    File.size() always responds with 0

                    Create a separate thread to handle the device, use (select () or poll ()) and signals to notify other classes or get to the GUI.
                    

                    How to use Can you provide any samples???

                    jsulmJ Offline
                    jsulmJ Offline
                    jsulm
                    Lifetime Qt Champion
                    wrote on last edited by
                    #14

                    @jigarp Take a look at what @SGaist suggested

                    https://forum.qt.io/topic/113070/qt-code-of-conduct

                    J 1 Reply Last reply
                    0
                    • jsulmJ jsulm

                      @jigarp Take a look at what @SGaist suggested

                      J Offline
                      J Offline
                      jigarp
                      wrote on last edited by jigarp
                      #15

                      @jsulm @SGaist
                      Not Working..

                      jsulmJ 1 Reply Last reply
                      -1
                      • J jigarp

                        @jsulm @SGaist
                        Not Working..

                        jsulmJ Offline
                        jsulmJ Offline
                        jsulm
                        Lifetime Qt Champion
                        wrote on last edited by
                        #16

                        @jigarp said in Reading devices under /dev/.:

                        Not Working..

                        Well, with such information it is impossible to say why it is not working.
                        Can you show what you tried and what the result was?

                        https://forum.qt.io/topic/113070/qt-code-of-conduct

                        1 Reply Last reply
                        0

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