linux-kernel - RE: [PATCH] thermal: sysfs: Fall back to vmalloc() for cooling device's statistics

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Message-ID: <7a0c2e488e024c0694fd730f95ba98fb@AcuMS.aculab.com>
Date:   Fri, 21 Aug 2020 08:39:45 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Yue Hu' <zbestahu@...il.com>,
        "rui.zhang@...el.com" <rui.zhang@...el.com>,
        "daniel.lezcano@...aro.org" <daniel.lezcano@...aro.org>,
        "amit.kucheria@...durent.com" <amit.kucheria@...durent.com>,
        "viresh.kumar@...aro.org" <viresh.kumar@...aro.org>
CC:     "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "huyue2@...ong.com" <huyue2@...ong.com>,
        "zhangwen@...ong.com" <zhangwen@...ong.com>
Subject: RE: [PATCH] thermal: sysfs: Fall back to vmalloc() for cooling
 device's statistics

From: Yue Hu
> Sent: 21 August 2020 03:44
> 
> From: Yue Hu <huyue2@...ong.com>
> 
> We observed warning about kzalloc() when register thermal cooling device
> in backlight_device_register(). backlight display can be a cooling device
> since reducing screen brightness will can help reduce temperature.
> 
> However, ->get_max_state of backlight will assign max brightness of 1024
> to states. The memory size can be getting 1MB+ due to states * states.
> That is so large to trigger kmalloc() warning.

I can't help feeling that there is an 'adequate' implementation
that doesn't require anywhere near 1MB of memory.

	David

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