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

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Message-ID: <20151122085155.GA4581@slacky>
Date:	Sun, 22 Nov 2015 09:51:56 +0100
From:	Dave Penkler <dpenkler@...il.com>
To:	Andy Shevchenko <andy.shevchenko@...il.com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	peter.chen@...escale.com, teuniz@...il.com,
	USB <linux-usb@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 5/5] Add ioctls to enable and disable local controls
 on an instrument

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@...il.com> wrote:
> > These ioctls provide support for the USBTMC-USB488 control requests
> > for REN_CONTROL, GO_TO_LOCAL and LOCAL_LOCKOUT
> 
> Couple of comments below.
> 
> > diff --git a/drivers/usb/class/usbtmc.c b/drivers/usb/class/usbtmc.c
> > index 2358991..d416a5f 100644
> > --- a/drivers/usb/class/usbtmc.c
> > +++ b/drivers/usb/class/usbtmc.c
> > @@ -476,6 +476,62 @@ static int usbtmc488_ioctl_read_stb(struct usbtmc_device_data *data,

snip

> 
> > +       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. 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.

> > +               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
cheers,
-Dave
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