linux-kernel - Re: [PATCH] PM: EM: Fix uninitialized power in em_create_perf

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Message-ID: <ZyiQnz4jbB5ChNxn@google.com>
Date: Mon, 4 Nov 2024 09:15:11 +0000
From: Quentin Perret <qperret@...gle.com>
To: Jinjie Ruan <ruanjinjie@...wei.com>
Cc: rafael@...nel.org, pavel@....cz, len.brown@...el.com,
	daniel.lezcano@...aro.org, lukasz.luba@....com,
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PM: EM: Fix uninitialized power in em_create_perf_table

Hi,

On Monday 04 Nov 2024 at 17:03:51 (+0800), Jinjie Ruan wrote:
> In em_create_perf_table(), power is uninitialized and passed the pointer
> to active_power() hook, but the hook function may not assign it and
> return 0, such as mtk_cpufreq_get_cpu_power(), so the later zero check for
> power is not invalid, initialize power to zero to fix it.

Sounds to me like a driver bug? We check the return value of
active_power() first, so if the callback failed it should tell us.

mtk_cpufreq_get_cpu_power() should only fail if we couldn't find a
cpufreq policy IIUC, so why can't this return -EINVAL instead?

Thanks,
Quentin