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

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Message-ID: <bb376229-006f-af16-2006-4ef9edea87f5@foss.st.com>
Date:   Thu, 22 Apr 2021 09:56:41 +0200
From:   Arnaud POULIQUEN <arnaud.pouliquen@...s.st.com>
To:     Mathieu Poirier <mathieu.poirier@...aro.org>
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 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]

[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
>>