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Bugs in USB Developers Package: Write Protection

Serge A
Expert 2665 points

Problem: once the write protection is set during the program execution via setting writeProtected flag in USBMSC_mediaInfoStr structure and calling USBMSC_updateMediaInfo(), it can not be reset back.

There is a bug in USB Developers Package, at least at revision 4.10.00 (the one I work with). To fix it go to UsbMscScsi.c file.

Scsi_Mode_Sense6() function: Replace

Scsi_Mode_Sense_6[2] |= (MscControl[McsCbw.bCBWLUN].bWriteProtected << 0x7);

with

Scsi_Mode_Sense_6[2] = (MscControl[McsCbw.bCBWLUN].bWriteProtected << 0x7);


Scsi_Mode_Sense10() function: Replace

Scsi_Mode_Sense_10[4] |= (MscControl[McsCbw.bCBWLUN].bWriteProtected << 0x7);

with

Scsi_Mode_Sense_10[4] = (MscControl[McsCbw.bCBWLUN].bWriteProtected << 0x7);

It fixes the bug.

  • TI__Guru* 77991 points

    Hi Serge,

    Thank you so much for reporting this - I'll notify the developers to make sure that this gets fixed.

    Regards,

    Katie

  • TI__Expert 6760 points

    Hello,

    I am looking into this issue.  Can you tell me what type of error you get when you try and reset the write protection flag?

    Aslo are you setting the write protection when MSC is being initialized and then resetting the flag in the main program?

     

    Regards,

    Arthi Bhat

  • in reply to Arthi Bhat1
    TI__Expert 6760 points

    Hello,

    If the write protection is set during execution time then it can be reset back during execution time by doing the following:

    USB_disconnect();

    USB_disable();

    mediaInfo.writeProtected = 0x00;

    USBMSC_updateMediaInfo(0, &mediaInfo);

    USB_enable();

    USB_reset();

    USB_connect();

     

    Regards,

    Arthi

     

  • in reply to Arthi Bhat1
    Expert 2665 points

    Arthi Bhat1 said:

    Hello,

    I am looking into this issue.  Can you tell me what type of error you get when you try and reset the write protection flag?

    Aslo are you setting the write protection when MSC is being initialized and then resetting the flag in the main program?

     

    Regards,

    Arthi Bhat

    Hi Arthi,

    There is no error generated while calling USBMSC_updateMediaInfo() for resetting write protection flag. It just does not perform actual reset of this flag. The host connected to this USB device still shows the volume as 'read only'. And the reason why it happens is shown and fixed in code that I included. Corresponding bit can not be reset by bitwise OR operation. I did consider it as a bug, fixed it and it seems to work since then without any problem. The workaround you've suggested may work as well, though it is not always desirable or possible to perform full USB stack re-initialisation.

     

    Best regards,

    Serge

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