linux-kernel - Re: [PATCH] ASoC: Intel: atom: Remove redundant check to simplify the code

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Message-ID: <YfA87pkRPA95aG2f@smile.fi.intel.com>
Date:   Tue, 25 Jan 2022 20:09:50 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
Cc:     Tang Bin <tangbin@...s.chinamobile.com>, broonie@...nel.org,
        cezary.rojewski@...el.com, liam.r.girdwood@...ux.intel.com,
        yang.jie@...ux.intel.com, perex@...ex.cz, tiwai@...e.com,
        alsa-devel@...a-project.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ASoC: Intel: atom: Remove redundant check to simplify
 the code

On Mon, Nov 29, 2021 at 10:22:41AM -0600, Pierre-Louis Bossart wrote:
> On 11/25/21 1:50 AM, Tang Bin wrote:

> > In the function sst_platform_get_resources(), if platform_get_irq()
> > failed, the return should not be zero, as the example in
> > platform.c is
> >   * int irq = platform_get_irq(pdev, 0)
> >   * if (irq < 0)
> >   * return irq;
> > So remove the redundant check to simplify the code.
> 
> Humm, it's a bit of a gray area.
> 
> the comments for platform_get_irq and platform_get_irq_optional say:
> 
> * Return: non-zero IRQ number on success, negative error number on failure.
> 
> but if you look at platform_get_irq_optional, there are two references
> to zero being a possible return value:
> 
> 	if (num == 0 && has_acpi_companion(&dev->dev)) {
> 		ret = acpi_dev_gpio_irq_get(ACPI_COMPANION(&dev->dev), num);
> 		/* Our callers expect -ENXIO for missing IRQs. */
> 		if (ret >= 0 || ret == -EPROBE_DEFER)

This is bogus == 0 check.

> 			goto out;
> 
> out_not_found:
> 	ret = -ENXIO;
> out:
> 	WARN(ret == 0, "0 is an invalid IRQ number\n");
> 	return ret;
> 
> https://elixir.bootlin.com/linux/latest/source/drivers/base/platform.c#L234
> 
> I am not sure if there's any merit in removing the test for the zero
> return value. It may be on the paranoid side but it's aligned with a
> possible code path in the platform code.
> 
> Or it could be that the platform code is wrong, and the label used
> should have been
> 
> /* Our callers expect -ENXIO for missing IRQs. */
> if (ret >= 0 || ret == -EPROBE_DEFER)
> 	goto out_not_found;

In case one wants to dive into new discussion on the topic:

https://lore.kernel.org/linux-serial/20220110195449.12448-2-s.shtylyov@omp.ru/T/#u

-- 
With Best Regards,
Andy Shevchenko