linux-kernel - Re: [PATCH] soc: qcom: icc-bwmon: Don't ignore return values of regmap functions

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Date:   Tue, 20 Jun 2023 11:14:51 -0700
From:   Bjorn Andersson <andersson@...nel.org>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     Konrad Dybcio <konrad.dybcio@...aro.org>,
        Andy Gross <agross@...nel.org>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] soc: qcom: icc-bwmon: Don't ignore return values of
 regmap functions

On Thu, Jun 15, 2023 at 11:26:13PM +0200, Krzysztof Kozlowski wrote:
> On 15/06/2023 23:12, Konrad Dybcio wrote:
> > As it turns out, not all regmap accesses succeed. Not knowing this is
> > particularly suboptimal when there's a breaking change to the regmap
> > APIs. Monitor the return values of regmap_ calls and propagate errors,
> > should any occur.
> > 
> > To keep any level of readability in bwmon_enable(), add some comments
> > to separate the logical blocks.
> > 
> > Signed-off-by: Konrad Dybcio <konrad.dybcio@...aro.org>
> 
> Nice coincidence, I just had some talks with a friend about uselessness
> (IMHO) of regmap MMIO return status checks.
> 
> Sorry, for me most of this makes the code difficult to read for no gain.
> Errors are not real. This is some artificial problem. Solving it makes
> code less maintainable.
> 
> If we used here readl/writel, you would not add any checks, right? Then
> don't add for regmap mmio.
> 

I agree, the mmio regmap interface should only fail because of bugs or
things are misconfigured. Would be nice to capture that in a WARN_ON()
or something...

Regards,
Bjorn