linux-kernel - Re: [PATCH v3 2/5] thermal/drivers/armada: convert to use devm_request_threaded_irq

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Date:   Tue, 4 Jul 2023 10:46:08 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Yangtao Li <frank.li@...o.com>
Cc:     rafael@...nel.org, daniel.lezcano@...aro.org, amitk@...nel.org,
        rui.zhang@...el.com, mmayer@...adcom.com,
        bcm-kernel-feedback-list@...adcom.com,
        florian.fainelli@...adcom.com, tglx@...utronix.de,
        matthias.bgg@...il.com, angelogioacchino.delregno@...labora.com,
        bchihi@...libre.com, wenst@...omium.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH v3 2/5] thermal/drivers/armada: convert to use
 devm_request_threaded_irq_emsg()

Hi Yangtao,

frank.li@...o.com wrote on Mon,  3 Jul 2023 17:04:51 +0800:

> There are more than 700 calls to the devm_request_threaded_irq method.
> Most drivers only request one interrupt resource, and these error
> messages are basically the same. If error messages are printed
> everywhere, more than 1000 lines of code can be saved by removing the
> msg in the driver.
> 
> And tglx point out that:
> 
>   If we actually look at the call sites of
>   devm_request_threaded_irq() then the vast majority of them print more or
>   less lousy error messages. A quick grep/sed/awk/sort/uniq revealed
> 
>      519 messages total (there are probably more)
> 
>      352 unique messages
> 
>      323 unique messages after lower casing
> 
>          Those 323 are mostly just variants of the same patterns with
>          slight modifications in formatting and information provided.
> 
>      186 of these messages do not deliver any useful information,
>          e.g. "no irq", "
> 
>      The most useful one of all is: "could request wakeup irq: %d"
> 
>   So there is certainly an argument to be made that this particular
>   function should print a well formatted and informative error message.
> 
>   It's not a general allocator like kmalloc(). It's specialized and in the
>   vast majority of cases failing to request the interrupt causes the
>   device probe to fail. So having proper and consistent information why
>   the device cannot be used _is_ useful.
> 
> Let's use devm_request_threaded_irq_emsg(), which ensure that all error
> handling branches print error information. In this way, when this function
> fails, the upper-layer functions can directly return an error code without
> missing debugging information. Otherwise, the error message will be
> printed redundantly or missing.
> 
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Signed-off-by: Yangtao Li <frank.li@...o.com>
> ---
>  drivers/thermal/armada_thermal.c | 13 +++++--------
>  1 file changed, 5 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/thermal/armada_thermal.c b/drivers/thermal/armada_thermal.c
> index 9f6dc4fc9112..a5e140643f00 100644
> --- a/drivers/thermal/armada_thermal.c
> +++ b/drivers/thermal/armada_thermal.c
> @@ -913,15 +913,12 @@ static int armada_thermal_probe(struct platform_device *pdev)
>  
>  	/* The overheat interrupt feature is not mandatory */
>  	if (irq > 0) {
> -		ret = devm_request_threaded_irq(&pdev->dev, irq,
> -						armada_overheat_isr,
> -						armada_overheat_isr_thread,
> -						0, NULL, priv);
> -		if (ret) {
> -			dev_err(&pdev->dev, "Cannot request threaded IRQ %d\n",
> -				irq);
> +		ret = devm_request_threaded_irq_emsg(&pdev->dev, irq,
> +						     armada_overheat_isr,
> +						     armada_overheat_isr_thread,
> +						     0, NULL, priv, NULL);
> +		if (ret)

I don't see a patch renaming this helper with s/emsg//, do you plan to
keep it like that? I bet nobody outside of this series will notice the
new helper and will continue to add error messages because it kind
of feels "right" to do so.

I would rather prefer returning to the original function name which
everybody knows/uses.

Anyhow, I'm fine with the idea of dropping custom error messages, so
whatever the final solution:

Acked-by: Miquel Raynal <miquel.raynal@...tlin.com>

Thanks,
Miquèl