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

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Message-ID: <5e63d822-5e19-7ab0-6ec7-a9ace4bdb706@foss.st.com>
Date:   Thu, 22 Apr 2021 18:41:52 +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 4/22/21 6:32 PM, Mathieu Poirier wrote:
> 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...

No worries, exploring alternatives is part of the upstream process  :)

> 
>>
>> [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
>>>>