linux-kernel - Re: [PATCH 22/24] thunderbolt: Add support for host and device NVM firmware upgrade

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Date:   Fri, 19 May 2017 11:26:10 +0300
From:   Mika Westerberg <mika.westerberg@...ux.intel.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andreas Noever <andreas.noever@...il.com>,
        Michael Jamet <michael.jamet@...el.com>,
        Yehezkel Bernat <yehezkel.bernat@...el.com>,
        Lukas Wunner <lukas@...ner.de>,
        Amir Levy <amir.jer.levy@...el.com>,
        Andy Lutomirski <luto@...nel.org>,
        Mario Limonciello <Mario.Limonciello@...l.com>,
        Jared.Dominguez@...l.com,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 22/24] thunderbolt: Add support for host and device NVM
 firmware upgrade

On Thu, May 18, 2017 at 10:35:19PM +0300, Andy Shevchenko wrote:
> On Thu, May 18, 2017 at 5:39 PM, Mika Westerberg
> <mika.westerberg@...ux.intel.com> wrote:
> > Starting from Intel Falcon Ridge the NVM firmware can be upgraded by
> > using DMA configuration based mailbox commands. If we detect that the
> > host or device (device support starts from Intel Alpine Ridge) has the
> > DMA configuration based mailbox we expose NVM information to the
> > userspace as two separate Linux NVMem devices: nvm_active and
> > nvm_non_active. The former is read-only portion of the active NVM which
> > firmware upgrade tools can be use to find out suitable NVM image if the
> > device identification strings are not enough.
> >
> > The latter is write-only portion where the new NVM image is to be
> > written by the userspace. It is up to the userspace to find out right
> > NVM image (the kernel does very minimal validation). The ICM firmware
> > itself authenticates the new NVM firmware and fails the operation if it
> > is not what is expected.
> >
> > We also expose two new sysfs files per each switch: nvm_version and
> > nvm_authenticate which can be used to read the active NVM version and
> > start the upgrade process.
> >
> > We also introduce safe mode which is the mode a switch goes when it does
> > not have properly authenticated firmware. In this mode the switch only
> > accepts a couple of commands including flashing a new NVM firmware image
> > and triggering power cycle.
> >
> > This code is based on the work done by Amir Levy and Michael Jamet.
> 
> Couple of nitpicks below.
> 
> > +static ssize_t nvm_authenticate_store(struct device *dev,
> > +       struct device_attribute *attr, const char *buf, size_t count)
> > +{
> > +       struct tb_switch *sw = tb_to_switch(dev);
> > +       unsigned int val;
> > +       int ret;
> > +
> > +       if (mutex_lock_interruptible(&switch_lock))
> > +               return -ERESTARTSYS;
> > +
> > +       ret = kstrtouint(buf, 0, &val);
> > +       if (ret)
> > +               goto unlock;
> 
> Looking below it would be
> ret = kstrtobool(..., &x);
> if (ret)
>  goto ...;
> 
> if (x) {
> } else {
> }
> 
> exit_unlock:
> ...

OK.

> > +
> > +       switch (val) {
> > +       case 0:
> > +               /* Just clear the authentication status */
> > +               nvm_clear_auth_status(sw);
> > +               break;
> > +
> > +       case 1:
> > +               ret = nvm_validate_and_write(sw);
> > +               if (ret)
> > +                       goto unlock;
> > +
> > +               sw->nvm->authenticating = true;
> > +
> > +               if (!tb_route(sw))
> > +                       ret = nvm_authenticate_host(sw);
> > +               else
> > +                       ret = nvm_authenticate_device(sw);
> > +               break;
> > +
> > +       default:
> > +               ret = -EINVAL;
> > +               break;
> > +       }
> > +
> > +unlock:
> > +       mutex_unlock(&switch_lock);
> > +
> > +       if (ret)
> > +               return ret;
> > +       return count;
> > +}
> 
> > +               nvm->major = val >> 16 & 0xff;
> > +               nvm->minor = val >> 8 & 0xff;
> 
> If lvalue is u8 or alike the conjunction becomes redundant.

It is indeed u8 so I can drop the & 0xff. Thanks.