linux-kernel - Re: [PATCH v2 1/3] platform/x86: Add Intel Input Output Manager (IOM) driver

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Message-ID: <20200824224726.GA48297@google.com>
Date:   Mon, 24 Aug 2020 15:47:26 -0700
From:   Prashant Malani <pmalani@...omium.org>
To:     "Mani, Rajmohan" <rajmohan.mani@...el.com>
Cc:     Darren Hart <dvhart@...radead.org>,
        Andy Shevchenko <andy@...radead.org>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Lee Jones <lee.jones@...aro.org>,
        Ayman Bagabas <ayman.bagabas@...il.com>,
        Masahiro Yamada <masahiroy@...nel.org>,
        "Joseph, Jithu" <jithu.joseph@...el.com>,
        Blaž Hrastnik <blaz@...n.io>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "platform-driver-x86@...r.kernel.org" 
        <platform-driver-x86@...r.kernel.org>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "bleung@...omium.org" <bleung@...omium.org>
Subject: Re: [PATCH v2 1/3] platform/x86: Add Intel Input Output Manager
 (IOM) driver

Hi Rajmohan,

On Mon, Aug 24, 2020 at 10:19:27PM +0000, Mani, Rajmohan wrote:
> Hi Prashant,
> 
> Thanks for the quick review.
> 
> > > +
> > > +	if (!iom || !iom->dev || !iom->regbar)
> > 
> > Do we need to check for !iom->dev and !iom->regbar?
> 
> It's a good practice to have sanity checks on pointer members dereferenced.
> 
> So I can lose the check on iom->dev, but prefer to keep the check on regbar.
> Let me know if you feel strongly about losing the check for regbar as well.

Sounds good.
> 
> > Is there a valid situation
> > where iom != NULL but iom->dev and/or iom->regbar == NULL?
> > Sounds like it shouldn't, but I may be missing something.
> > 
> 
> I think I am being conservative here.
> 
> > > +		return -ENODEV;
> > > +
> > > +	if (!status || (port > IOM_MAX_PORTS - 1))
> > 
> > I think parentheses around "port > IOM_MAX_PORT - 1" aren't required.
> 
> Ack
> 
> > > +		return -EINVAL;
> > > +
> > > +	reg = iom->regbar + IOM_PORT_STATUS_OFFSET + IOM_REG_LEN *
> > port;
> > > +
> > > +	*status = ioread32(reg);
> > 
> > Perhaps just inline reg within the parentheses?
> 
> Kept this way to increase readability. Let me know if you feel strongly towards
> inline reg.

I'd rather this be inlined, you save a couple lines from the variable
declaration, and IMO we're not gaining much in terms of readability by
declaring this separately.

> 
> > > +
> > > +	return 0;
> > > +}
> > > +EXPORT_SYMBOL_GPL(intel_iom_port_status);
> > > +
> > > +static int intel_iom_probe(struct platform_device *pdev) {
> > > +	void __iomem *addr;
> > > +
> > > +	/* only one IOM device is supported */
> > 
> > Minor nit: s/only/Only
> 
> And then I may need to end the comment with a period.
> Let me know if you feel strongly.
Yes, let's capitalize and add the period. Let's try to use the right
punctuation where possible.

Best regards,

-Prashant