linux-kernel - Re: [PATCH v3 1/4] remoteproc: core: Move cdev add before device add

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Message-ID: <YMgy7eg3wde0eVfe@kroah.com>
Date:   Tue, 15 Jun 2021 06:56:13 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Siddharth Gupta <sidgup@...eaurora.org>
Cc:     bjorn.andersson@...aro.org, ohad@...ery.com,
        linux-remoteproc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, psodagud@...eaurora.org,
        stable@...r.kernel.org
Subject: Re: [PATCH v3 1/4] remoteproc: core: Move cdev add before device add

On Mon, Jun 14, 2021 at 07:21:08PM -0700, Siddharth Gupta wrote:
> When cdev_add is called after device_add has been called there is no
> way for the userspace to know about the addition of a cdev as cdev_add
> itself doesn't trigger a uevent notification, or for the kernel to
> know about the change to devt. This results in two problems:
>  - mknod is never called for the cdev and hence no cdev appears on
>    devtmpfs.
>  - sysfs links to the new cdev are not established.
> 
> The cdev needs to be added and devt assigned before device_add() is
> called in order for the relevant sysfs and devtmpfs entries to be
> created and the uevent to be properly populated.

So this means no one ever ran this code on a system that used devtmpfs?

How was it ever tested?