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

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Message-ID: <20200821170627.00003d5e.zbestahu@gmail.com>
Date:   Fri, 21 Aug 2020 17:06:27 +0800
From:   Yue Hu <zbestahu@...il.com>
To:     David Laight <David.Laight@...LAB.COM>
Cc:     "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>,
        "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

On Fri, 21 Aug 2020 08:39:45 +0000
David Laight <David.Laight@...LAB.COM> wrote:

> 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.

However, it should be a potential issue due to what i described above, rt?

Thx.

> 
> 	David
> 
> -
> Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
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