linux-kernel - Re: [PATCH v3 6/7] iio: pressure: bmp280: Add data ready trigger support

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Message-ID: <ZsxXvGy4GNrZWs-D@smile.fi.intel.com>
Date: Mon, 26 Aug 2024 13:23:56 +0300
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Vasileios Amoiridis <vassilisamir@...il.com>
Cc: jic23@...nel.org, lars@...afoo.de, robh@...nel.org, krzk+dt@...nel.org,
	conor+dt@...nel.org, ang.iglesiasg@...il.com,
	linus.walleij@...aro.org, biju.das.jz@...renesas.com,
	javier.carrasco.cruz@...il.com, semen.protsenko@...aro.org,
	579lpy@...il.com, ak@...klinger.de, linux-iio@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 6/7] iio: pressure: bmp280: Add data ready trigger
 support

On Sat, Aug 24, 2024 at 02:02:22PM +0200, Vasileios Amoiridis wrote:
> On Fri, Aug 23, 2024 at 11:06:28PM +0300, Andy Shevchenko wrote:
> > On Fri, Aug 23, 2024 at 08:17:13PM +0200, Vasileios Amoiridis wrote:

...

> > > +static int __bmp280_trigger_probe(struct iio_dev *indio_dev,
> > > +				  const struct iio_trigger_ops *trigger_ops,
> > > +				  int (*int_config)(struct bmp280_data *data),
> > 
> > > +				  irqreturn_t (*irq_thread_handler)(int irq, void *p))
> > 
> > irq_handler_t
> 
> But the function returns an irqreturn_t type, no?

The type of the last parameter is irq_handler_t, no need to open code it.

...

> > > +	fwnode = dev_fwnode(data->dev);
> > > +	if (!fwnode)
> > > +		return -ENODEV;
> > 
> > Why do you need this? The below will fail anyway.
> 
> Because If I don't make this check then fwnode might be garbage and I will
> pass garbage to the fwnode_irq_get() function. Or do I miss something?

Yes, the function validates fwnode before use. So, please drop unneeded (or
even duplicate) check.

...

> > > +	irq = fwnode_irq_get(fwnode, 0);
> > > +	if (!irq)
> > 
> > Are you sure this is correct check?
> > 
> Well, I think yes, because the function return either the Linux IRQ number
> on success or a negative errno on failure.

Where is 0 mentioned in this?

> https://elixir.bootlin.com/linux/v6.10.6/source/drivers/base/property.c#L987
> 
> > > +		return dev_err_probe(data->dev, -ENODEV,
> > 
> > Shadowed error code.
> 
> I am not sure I understand what you mean here. You mean that there is no
> chance that the first one will pass and this one will fail?

-ENODEV is not what fwnode_irq_get() returns on error.

> > > +				     "No interrupt found.\n");

...

> > > +	desc = irq_get_irq_data(irq);
> > > +	if (!desc)
> > > +		return -EINVAL;
> > 
> > When may this fail?
> 
> I think that this will fail when Linux were not able to actually
> register that interrupt.

Wouldn't fwnode_irq_get() fail already?

...

> > 	if (ret)
> > 		dev_err(data->dev, "Could not enable/disable interrupt\n");

Btw you may use str_enable_disable() here.

> > 	return ret;
> > 
> > ?
> 
> All the other if statements follow the style that I typed. If I
> follow yours, will make it different just for this one, does it
> make sense?

When a comment is given, it's assumed that the _full_ patch (or patch series)
should be revisited for it. Or should I add to every comment something like
this:

"Please, check the entire code for the same or similar case and amend
accordingly."

?

-- 
With Best Regards,
Andy Shevchenko