linux-kernel - Re: [PATCH v5 3/4] rpmsg: Move the rpmsg control device from rpmsg_char to rpmsg

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Message-ID: <YWDVwArEz5Yub3GJ@ripper>
Date:   Fri, 8 Oct 2021 16:35:28 -0700
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Arnaud Pouliquen <arnaud.pouliquen@...s.st.com>
Cc:     Ohad Ben-Cohen <ohad@...ery.com>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        linux-remoteproc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com
Subject: Re: [PATCH v5 3/4] rpmsg: Move the rpmsg control device from
 rpmsg_char to rpmsg_ctrl

On Mon 12 Jul 05:37 PDT 2021, Arnaud Pouliquen wrote:

> Create the rpmsg_ctrl.c module and move the code related to the
> rpmsg_ctrldev device in this new module.
> 
> Add the dependency between rpmsg_char and rpmsg_ctrl in the
> kconfig file.
> 

As I said in the cover letter, the only reason I can see for doing this
refactoring is in relation to the introduction of
RPMSG_CREATE_DEV_IOCTL. So I would like this patch to go together with
that patch, together with a good motivation why there's merit to
creating yet another kernel module (and by bind/unbind can't be used).

Perhaps I'm just missing some good usecase related to this?

> Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@...s.st.com>
> Reviewed-by: Mathieu Poirier <mathieu.poirier@...aro.org>
> ---
>  drivers/rpmsg/Kconfig      |   9 ++
>  drivers/rpmsg/Makefile     |   1 +
>  drivers/rpmsg/rpmsg_char.c | 170 +----------------------------
>  drivers/rpmsg/rpmsg_char.h |   2 +
>  drivers/rpmsg/rpmsg_ctrl.c | 215 +++++++++++++++++++++++++++++++++++++
>  5 files changed, 229 insertions(+), 168 deletions(-)
>  create mode 100644 drivers/rpmsg/rpmsg_ctrl.c
> 
[..]
> diff --git a/drivers/rpmsg/rpmsg_char.c b/drivers/rpmsg/rpmsg_char.c
[..]
> -static int rpmsg_chrdev_probe(struct rpmsg_device *rpdev)
> -{
[..]
> -	dev = &ctrldev->dev;
> -	device_initialize(dev);
> -	dev->parent = &rpdev->dev;
> -	dev->class = rpmsg_class;
[..]
> diff --git a/drivers/rpmsg/rpmsg_ctrl.c b/drivers/rpmsg/rpmsg_ctrl.c
[..]
> +static int rpmsg_ctrldev_probe(struct rpmsg_device *rpdev)
> +{
[..]
> +	dev = &ctrldev->dev;
> +	device_initialize(dev);
> +	dev->parent = &rpdev->dev;

You lost the assignment of dev->class here, which breaks the udev rules
we use to invoke rpmsgexport to create endpoints and it causes udevadm
to complain that rpmsg_ctrlN doesn't have a "subsystem".

Regards,
Bjorn