linux-kernel - Re: [PATCH 1/3] thermal: exynos: Fix NULL pointer exception during kernel booting

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Date:	Tue, 17 Feb 2015 01:15:20 +0900
From:	Chanwoo Choi <cwchoi00@...il.com>
To:	Lukasz Majewski <l.majewski@...sung.com>
Cc:	Zhang Rui <rui.zhang@...el.com>,
	Eduardo Valentin <edubezval@...il.com>,
	Kukjin Kim <kgene@...nel.org>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Amit Kachhap <amit.daniel@...sung.com>,
	Abhilash Kesavan <a.kesavan@...sung.com>,
	"inki.dae@...sung.com" <inki.dae@...sung.com>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
	linux-samsung-soc <linux-samsung-soc@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] thermal: exynos: Fix NULL pointer exception during
 kernel booting

Hi Lukasz,

On Tue, Feb 17, 2015 at 12:06 AM, Lukasz Majewski
<l.majewski@...sung.com> wrote:
> Hi Chanwoo,
>
>> This patch fixes the NULL pointer exception during kernel booting.
>> The thermal_zone _of_sensor_register() registers a sensor to DT
>> thermal zone and then read the current temperature by '.get_temp'
>> callback. The callback function of exynos thermal driver is
>> exynos_get_temp() which must need the 'pdata' instance of exynos_tmu
>> _platform_data structure.
>> - exynos_get_temp() -> code_to_temp() -> Must need the 'pdata'
>> instance
>>
>> But, exynos thermal driver is executed before getting the 'pdata'
>> instance. To avoid the kernel panic, have to get the platform data by
>> executing the exynos_map_dt_data() before calling
>> thermal_zone_of_sensor_register() .
>
> I've already prepared patch for this (unfortunately it isn't yet
> applied to mainline):
>
> "[PATCH] thermal: exynos: fix: Check if data->tmu_read callback is
> present before read"
>
> http://www.spinics.net/lists/linux-samsung-soc/msg42245.html

There is different issue between you patch and this patch.
Your patch check the whether data->tmu_read is NULL or not.
But, my patch check the pdata is NULL or not.

>
> Does applying this patch help?
>
> BTW: How can I reproduce this error? Could you point me the SHA1 and
> repository?

I used your patch-set of linux-soc-thermal.git (branch: next). So I
applied you patchiest on Linux 3.19 for test.
- https://git.kernel.org/cgit/linux/kernel/git/evalenti/linux-soc-thermal.git/log/?h=next

Best Regards,
Chanwoo Choi
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