linux-kernel - Re: [PATCH] sound: sof: ioc4-topology: avoid extra dai

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Message-ID: <731fa66a-bed7-45fb-9187-a9263612eac4@sirena.org.uk>
Date: Wed, 7 Aug 2024 16:09:18 +0100
From: Mark Brown <broonie@...nel.org>
To: Arnd Bergmann <arnd@...nel.org>
Cc: Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
	Liam Girdwood <lgirdwood@...il.com>,
	Peter Ujfalusi <peter.ujfalusi@...ux.intel.com>,
	Bard Liao <yung-chuan.liao@...ux.intel.com>,
	Ranjani Sridharan <ranjani.sridharan@...ux.intel.com>,
	Daniel Baluta <daniel.baluta@....com>,
	Seppo Ingalsuo <seppo.ingalsuo@...ux.intel.com>,
	Arnd Bergmann <arnd@...db.de>,
	Kai Vehmanen <kai.vehmanen@...ux.intel.com>,
	Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.com>,
	Nathan Chancellor <nathan@...nel.org>,
	Nick Desaulniers <ndesaulniers@...gle.com>,
	Bill Wendling <morbo@...gle.com>,
	Justin Stitt <justinstitt@...gle.com>,
	Brent Lu <brent.lu@...el.com>, sound-open-firmware@...a-project.org,
	linux-sound@...r.kernel.org, linux-kernel@...r.kernel.org,
	llvm@...ts.linux.dev
Subject: Re: [PATCH] sound: sof: ioc4-topology: avoid extra dai_params copy

On Wed, Aug 07, 2024 at 10:02:27AM +0200, Arnd Bergmann wrote:

> From what I can tell, this was unintentional, as both
> sof_ipc4_prepare_dai_copier() and sof_ipc4_prepare_copier_module() make a
> copy for the same purpose, but copying it once has the exact same effect.

> Remove the extra copy and change the direct struct assignment to
> an explicit memcpy() call to make it clearer to the reader that this
> is what happens. Note that gcc treats struct assignment as a memcpy()
> that may be inlined anyway, so the resulting object code is the same.

The effect of the copy is to ensure that if the function fails the
argument is unmodified - did you do the analysis to check that it's OK
to modify on error?  Your commit log says "the same purpose" but never
specifies what that purpose is.

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