linux-kernel - Re: [PATCH v2 1/5] pwm: dwc: drop redundant error check

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Message-ID: <ZcUJoSMhgC7lhY-H@smile.fi.intel.com>
Date: Thu, 8 Feb 2024 19:04:33 +0200
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
Cc: Raag Jadav <raag.jadav@...el.com>, jarkko.nikula@...ux.intel.com,
	mika.westerberg@...ux.intel.com, lakshmi.sowjanya.d@...el.com,
	linux-pwm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/5] pwm: dwc: drop redundant error check

On Thu, Feb 08, 2024 at 08:46:44AM +0100, Uwe Kleine-König wrote:
> On Thu, Feb 08, 2024 at 12:35:25PM +0530, Raag Jadav wrote:
> > pcim_iomap_table() fails only if pcim_iomap_regions() fails. No need to
> > check for failure if the latter is already successful.
> 
> Is this really true? pcim_iomap_table() calls devres_alloc_node() which
> might fail if the allocation fails. (Yes, I know
> https://lwn.net/Articles/627419/, but the rule is still to check for
> errors, right?)

We do not add a dead code to the kernel, right?

> What am I missing?

Mysterious ways of the twisted PCI devres code.
Read the above commit message again :-)

For your convenience I can elaborate. pcim_iomap_table() calls _first_
devres_find() which _will_ succeed if the pcim_iomap_regions() previously
succeeded. Does it help to understand how it designed?

-- 
With Best Regards,
Andy Shevchenko