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SubjectRe: [Regression] Missing device nodes for ETR, ETF and STM after CONFIG_UEVENT_HELPER=n
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On 7/26/2019 12:34 PM, Greg Kroah-Hartman wrote:
> On Fri, Jul 26, 2019 at 11:49:19AM +0530, Sai Prakash Ranjan wrote:
>> Hi,
>>
>> When trying to test my coresight patches, I found that etr,etf and stm
>> device nodes are missing from /dev.
>
> I have no idea what those device nodes are.
>
>> Bisection gives this as the bad commit.
>>
>> 1be01d4a57142ded23bdb9e0c8d9369e693b26cc is the first bad commit
>> commit 1be01d4a57142ded23bdb9e0c8d9369e693b26cc
>> Author: Geert Uytterhoeven <geert+renesas@glider.be>
>> Date: Thu Mar 14 12:13:50 2019 +0100
>>
>> driver: base: Disable CONFIG_UEVENT_HELPER by default
>>
>> Since commit 7934779a69f1184f ("Driver-Core: disable /sbin/hotplug by
>> default"), the help text for the /sbin/hotplug fork-bomb says
>> "This should not be used today [...] creates a high system load, or
>> [...] out-of-memory situations during bootup". The rationale for this
>> was that no recent mainstream system used this anymore (in 2010!).
>>
>> A few years later, the complete uevent helper support was made optional
>> in commit 86d56134f1b67d0c ("kobject: Make support for uevent_helper
>> optional."). However, if was still left enabled by default, to support
>> ancient userland.
>>
>> Time passed by, and nothing should use this anymore, so it can be
>> disabled by default.
>>
>> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
>> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>>
>> drivers/base/Kconfig | 1 -
>> 1 file changed, 1 deletion(-)
>>
>>
>> Any idea on this?
>
> That means that who ever created those device nodes is relying on udev
> to do this, and is not doing the correct thing within the kernel and
> using devtmpfs.
>
> Any pointers to where in the kernel those devices are trying to be
> created?
>

Somewhere in drivers/hwtracing/coresight/* probably. I am not sure,
Mathieu/Suzuki would be able to point you to the exact code.

Also just to add on some more details, I am using *initramfs*

Thanks,
Sai

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