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Re: [PATCH v5 5/5] Add ioctls to enable and disable local controls on an instrument

From Andy Shevchenko <andy.shevchenko@gmail.com>
Newsgroups linux.kernel
Subject Re: [PATCH v5 5/5] Add ioctls to enable and disable local controls on an instrument
Date 2015-11-22 11:40 +0100
Message-ID <qxAdP-2sv-17@gated-at.bofh.it> (permalink)
References <qw6rv-qW-5@gated-at.bofh.it> <qw6rw-qW-15@gated-at.bofh.it> <qw7xg-17g-7@gated-at.bofh.it> <qxyF3-1jE-1@gated-at.bofh.it>
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On Sun, Nov 22, 2015 at 10:51 AM, Dave Penkler <dpenkler@gmail.com> wrote:
> On Wed, Nov 18, 2015 at 11:41:30AM +0200, Andy Shevchenko wrote:
>> On Wed, Nov 18, 2015 at 10:38 AM, Dave Penkler <dpenkler@gmail.com> wrote:


>> > +       if (rv < 0) {
>> > +               dev_err(dev, "simple usb_control_msg failed %d\n", rv);
>> > +               goto exit;
>> > +       } else if (rv != 1) {
>> > +               dev_warn(dev, "simple usb_control_msg returned %d\n", rv);
>>
>> Actually here what king of results could be? 0? 2+? In all cases of
>> error you have to provide an error code.
>>
>
> We seem to be going round in circles here, last time you suggested to
> propagate the return value.

You didn't pay much attention to where I put my comment. You have few
branches depending on return value

1) negative, apparently an error code, should be propagated if nothing
specific to framework;
2) zero, what does it means?
3) one, seems the expected result when success, so, error code should be 0;
4) two, three, … non-negative numbers,see 2).

For my understanding 2) and 4) have to return what you initially had -EIO.

> The non-negative return is the number of bytes
> transferred which should be 1 unless there is some usb implementation
> flakiness happening. So I will go back to returning -EIO.

Yes, in *this* branch.

>
>> > +               goto exit;
>> > +       }
>> > +
>> > +       if (buffer[0] != USBTMC_STATUS_SUCCESS) {
>> > +               dev_err(dev, "simple control status returned %x\n", buffer[0]);
>> > +               rv = -EIO;
>> > +               goto exit;
>> > +       }
>> > +       rv = 0;
>> > +
>> > + exit:
>> > +       kfree(buffer);
>> > +       return rv;
>> > +}

-- 
With Best Regards,
Andy Shevchenko
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Thread

[PATCH v5 0/5] usb: usbtmc: Add support for missing functions in  USBTMC-USB488 spec Dave Penkler <dpenkler@gmail.com> - 2015-11-18 09:40 +0100
  [PATCH v5 1/5] Implement an ioctl to support the USMTMC-USB488  READ_STATUS_BYTE operation. Dave Penkler <dpenkler@gmail.com> - 2015-11-18 09:40 +0100
    Re: [PATCH v5 1/5] Implement an ioctl to support the USMTMC-USB488  READ_STATUS_BYTE operation. Andy Shevchenko <andy.shevchenko@gmail.com> - 2015-11-18 11:00 +0100
      Re: [PATCH v5 1/5] Implement an ioctl to support the USMTMC-USB488  READ_STATUS_BYTE operation. Dave Penkler <dpenkler@gmail.com> - 2015-11-22 10:30 +0100
        Re: [PATCH v5 1/5] Implement an ioctl to support the USMTMC-USB488  READ_STATUS_BYTE operation. Andy Shevchenko <andy.shevchenko@gmail.com> - 2015-11-22 11:40 +0100
          Re: [PATCH v5 1/5] Implement an ioctl to support the USMTMC-USB488  READ_STATUS_BYTE operation. Dave Penkler <dpenkler@gmail.com> - 2015-11-25 10:20 +0100
            Re: [PATCH v5 1/5] Implement an ioctl to support the USMTMC-USB488  READ_STATUS_BYTE operation. Andy Shevchenko <andy.shevchenko@gmail.com> - 2015-11-25 21:40 +0100
              Re: [PATCH v5 1/5] Implement an ioctl to support the USMTMC-USB488  READ_STATUS_BYTE operation. Dave Penkler <dpenkler@gmail.com> - 2015-11-28 13:00 +0100
                Re: [PATCH v5 1/5] Implement an ioctl to support the USMTMC-USB488  READ_STATUS_BYTE operation. Andy Shevchenko <andy.shevchenko@gmail.com> - 2015-11-28 16:00 +0100
                Re: [PATCH v5 1/5] Implement an ioctl to support the USMTMC-USB488  READ_STATUS_BYTE operation. Dave Penkler <dpenkler@gmail.com> - 2015-11-28 18:50 +0100
                Re: [PATCH v5 1/5] Implement an ioctl to support the USMTMC-USB488  READ_STATUS_BYTE operation. Andy Shevchenko <andy.shevchenko@gmail.com> - 2015-11-28 20:20 +0100
  [PATCH v5 2/5] Add support for USBTMC USB488 SRQ notification with  fasync Dave Penkler <dpenkler@gmail.com> - 2015-11-18 09:40 +0100
  [PATCH v5 5/5] Add ioctls to enable and disable local controls on an  instrument Dave Penkler <dpenkler@gmail.com> - 2015-11-18 09:40 +0100
    Re: [PATCH v5 5/5] Add ioctls to enable and disable local controls on  an instrument Andy Shevchenko <andy.shevchenko@gmail.com> - 2015-11-18 10:50 +0100
      Re: [PATCH v5 5/5] Add ioctls to enable and disable local controls  on an instrument Dave Penkler <dpenkler@gmail.com> - 2015-11-22 10:00 +0100
        Re: [PATCH v5 5/5] Add ioctls to enable and disable local controls on  an instrument Andy Shevchenko <andy.shevchenko@gmail.com> - 2015-11-22 11:40 +0100
          Re: [PATCH v5 5/5] Add ioctls to enable and disable local controls  on an instrument Dave Penkler <dpenkler@gmail.com> - 2015-11-25 10:20 +0100
            Re: [PATCH v5 5/5] Add ioctls to enable and disable local controls on  an instrument Andy Shevchenko <andy.shevchenko@gmail.com> - 2015-11-25 21:50 +0100
  [PATCH v5 4/5] Add ioctl to retrieve USBTMC-USB488 capabilities Dave Penkler <dpenkler@gmail.com> - 2015-11-18 09:40 +0100

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