linux-kernel - Re: [PATCH v2 2/7] rpmsg: Move the rpmsg control device from rpmsg_char to rpmsg

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Date:   Thu, 22 Apr 2021 10:32:17 -0600
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     Arnaud POULIQUEN <arnaud.pouliquen@...s.st.com>
Cc:     Bjorn Andersson <bjorn.andersson@...aro.org>,
        Ohad Ben-Cohen <ohad@...ery.com>,
        linux-remoteproc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com
Subject: Re: [PATCH v2 2/7] rpmsg: Move the rpmsg control device from
 rpmsg_char to rpmsg_ctrl

On Thu, Apr 22, 2021 at 09:56:41AM +0200, Arnaud POULIQUEN wrote:
> 
> 
> On 4/21/21 8:04 PM, Mathieu Poirier wrote:
> > On Tue, Apr 13, 2021 at 03:44:53PM +0200, 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.
> >>
> >> Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@...s.st.com>
> >> ---
> >> update from v1:
> >> - keep "rpmsg_chrdev" driver name in rpmsg_ctrl, driver will be renamed
> >>   in next path that renames the rpmsg_chrdev_create_eptdev.
> >> - rename the chardev regions
> >> - move RPMSG_DEV_MAX to rpmsg_char.h
> >> ---
> >>  drivers/rpmsg/Kconfig      |   9 ++
> >>  drivers/rpmsg/Makefile     |   1 +
> >>  drivers/rpmsg/rpmsg_char.c | 181 +----------------------------
> >>  drivers/rpmsg/rpmsg_char.h |   2 +
> >>  drivers/rpmsg/rpmsg_ctrl.c | 231 +++++++++++++++++++++++++++++++++++++
> >>  5 files changed, 245 insertions(+), 179 deletions(-)
> >>  create mode 100644 drivers/rpmsg/rpmsg_ctrl.c
> >>
> >> diff --git a/drivers/rpmsg/Kconfig b/drivers/rpmsg/Kconfig
> >> index 0b4407abdf13..d822ec9ec692 100644
> >> --- a/drivers/rpmsg/Kconfig
> 
> snip[...]
> 
> >> +static int rpmsg_ctrldev_init(void)
> >> +{
> >> +	int ret;
> >> +
> >> +	ret = alloc_chrdev_region(&rpmsg_major, 0, RPMSG_DEV_MAX, "rpmsg_ctrl");
> >> +	if (ret < 0) {
> >> +		pr_err("rpmsg: failed to allocate char dev region\n");
> >> +		return ret;
> >> +	}
> >> +
> >> +	rpmsg_class = class_create(THIS_MODULE, "rpmsg");
> > 
> > This class thing really bothers me.  Keeping this here means that rpmsg_eptdevs
> > created from user space will be associated to this rpmsg_class but those created
> > from the name service won't.  As such I propose to move this to rpmsg_char and
> > simply not associate the control device to the class.
> > 
> > Otherwise we'd have to introduce some mechanic only to deal with the creation of
> > the class and I don't think it is worth.  We can revise that approach if someone
> > complains we broke their user space. 
> 
> I agree with that as it was my first proposed approach here [1]

Yeah, sorry about that.  This patch review process is not an exact science...

> 
> [1] https://www.spinics.net/lists/linux-arm-msm/msg81194.html
> 
> Thanks,
> Arnaud
> 
> > 
> > 
> >> +	if (IS_ERR(rpmsg_class)) {
> >> +		pr_err("failed to create rpmsg class\n");
> >> +		ret = PTR_ERR(rpmsg_class);
> >> +		goto free_region;
> >> +	}
> >> +
> >> +	ret = register_rpmsg_driver(&rpmsg_ctrldev_driver);
> >> +	if (ret < 0) {
> >> +		pr_err("rpmsg ctrl: failed to register rpmsg driver\n");
> >> +		goto free_class;
> >> +	}
> >> +
> >> +	return 0;
> >> +
> >> +free_class:
> >> +	class_destroy(rpmsg_class);
> >> +free_region:
> >> +	unregister_chrdev_region(rpmsg_major, RPMSG_DEV_MAX);
> >> +
> >> +	return ret;
> >> +}
> >> +postcore_initcall(rpmsg_ctrldev_init);
> >> +
> >> +static void rpmsg_ctrldev_exit(void)
> >> +{
> >> +	unregister_rpmsg_driver(&rpmsg_ctrldev_driver);
> >> +	class_destroy(rpmsg_class);
> >> +	unregister_chrdev_region(rpmsg_major, RPMSG_DEV_MAX);
> >> +}
> >> +module_exit(rpmsg_ctrldev_exit);
> >> +
> >> +MODULE_DESCRIPTION("rpmsg control interface");
> >> +MODULE_ALIAS("rpmsg:" KBUILD_MODNAME);
> >> +MODULE_LICENSE("GPL v2");
> >> -- 
> >> 2.17.1
> >>