linux-kernel - Re: [PATCH v10 3/5] iio: adc: Add Xilinx AMS driver

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Date:   Thu, 18 Nov 2021 17:42:31 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Anand Ashok Dumbre <ANANDASH@...inx.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "jic23@...nel.org" <jic23@...nel.org>,
        "lars@...afoo.de" <lars@...afoo.de>,
        "linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
        git <git@...inx.com>, Michal Simek <michals@...inx.com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "rafael@...nel.org" <rafael@...nel.org>,
        "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
        "heikki.krogerus@...ux.intel.com" <heikki.krogerus@...ux.intel.com>,
        Manish Narani <MNARANI@...inx.com>
Subject: Re: [PATCH v10 3/5] iio: adc: Add Xilinx AMS driver

On Thu, Nov 18, 2021 at 02:14:41PM +0000, Anand Ashok Dumbre wrote:
> > From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> > Sent: Wednesday 17 November 2021 8:03 PM
> > On Wed, Nov 17, 2021 at 04:10:26PM +0000, Anand Ashok Dumbre wrote:

...

> > > +			ret = ams_read_vcc_reg(ams, chan->address, val);
> > > +			if (ret) {
> > > +				mutex_unlock(&ams->lock);
> > > +				return -EINVAL;
> > 
> > Shadowed error code.
> 
> I don’t understand.

You get an error code in ret variable, but you always return -EINVAL, why?

> > > +			}

...

> > default: ?
> 
> This is limited by hw bits.
> For default I will use the default scan_index value.
> Is that ok?

I think so, you know hardware better, you decide what to put there.

...

> > > +		if (ret || reg > (AMS_PL_MAX_EXT_CHANNEL + 30))
> > 
> > Too many parentheses.
> 
> Is it a good practice to not have parantheses around (AMS_PL_MAX_EXT_CHANNEL + 30) ?

It's minor thing, up to you.

> > > +			continue;

...

> > > +	dev_chan_size = array_size((size_t)num_channels, sizeof(struct
> > iio_chan_spec));
> > > +	if (dev_chan_size == SIZE_MAX)
> > > +		return -EINVAL;
> > 
> > Why is it needed now?
> > 
> > > +	dev_channels = devm_kcalloc(&pdev->dev, (size_t)num_channels,
> > 
> > Why casting?
> > 
> > > +				    sizeof(struct iio_chan_spec), GFP_KERNEL);
> > 
> > sizeof(*dev_channels)
> > 
> > > +	if (!dev_channels) {
> > > +		ret = -ENOMEM;
> > > +		goto free_mem;
> > > +	}
> > 
> > > +	memcpy(dev_channels, ams_channels,
> > > +	       sizeof(*ams_channels) * num_channels);
> > 
> > Hmm... according to the code the num_channels can be less than or equal to
> > num_chan. Hence, what you should use is the devm_krealloc_array().
> > 
> > static inline void *devm_krealloc_aray(...) {
> > 	...see how krealloc_array() is defined...
> > }
> > 
> > No need to copy memory again.
> 
> Will take a look.

-- 
With Best Regards,
Andy Shevchenko