linux-kernel - Re: [PATCH v5 15/16] rpmsg: char: no dynamic endpoint management for the default one

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Date:   Fri, 5 Mar 2021 12:09:37 +0100
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>,
        Andy Gross <agross@...nel.org>,
        <linux-remoteproc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <linux-arm-msm@...r.kernel.org>
Subject: Re: [PATCH v5 15/16] rpmsg: char: no dynamic endpoint management for
 the default one



On 3/4/21 7:40 PM, Mathieu Poirier wrote:
> There has to be a capital letter at the start of the title:
> 
> rpmsg: char: No dynamic endpoint management for the default one
> 
> Please fix for all the patches.

Ok, I will update the subjects with capital letter in my next revision.

Just for my information, is it a new rule? kernel documentation [1] gives a
canonical subject and an example without capital letter.

[1]
https://www.kernel.org/doc/html/v4.17/process/submitting-patches.html#the-canonical-patch-format

> 
> On Fri, Feb 19, 2021 at 12:15:00PM +0100, Arnaud Pouliquen wrote:
>> Do not dynamically manage the default endpoint. The ept address must
>> not change.
>> This update is needed to manage the RPMSG_CREATE_DEV_IOCTL. In this
>> case a default endpoint is used and it's address must not change or
>> been reused by another service.
> 
> The above is very difficult to understand.  I am not sure about introducing
> RPMSG_CREATE_DEV_IOCTL in this patchset.  More on that in an upcoming comment.

The purpose of this revision was mainly to provide a view of what we could do to
provide a more generic control interface.

To simplify the review I can remove the RPMSG_CREATE_DEV_IOCTL management and
send it as a next step, in a separate patchset.

> 
>>
>> Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@...s.st.com>
>> ---
>>  drivers/rpmsg/rpmsg_char.c | 28 +++++++++++++++++++++-------
>>  1 file changed, 21 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/rpmsg/rpmsg_char.c b/drivers/rpmsg/rpmsg_char.c
>> index c98b0e69679b..8d3f9d6c20ad 100644
>> --- a/drivers/rpmsg/rpmsg_char.c
>> +++ b/drivers/rpmsg/rpmsg_char.c
>> @@ -114,14 +114,23 @@ static int rpmsg_eptdev_open(struct inode *inode, struct file *filp)
>>  	struct rpmsg_endpoint *ept;
>>  	struct rpmsg_device *rpdev = eptdev->rpdev;
>>  	struct device *dev = &eptdev->dev;
>> +	u32 addr = eptdev->chinfo.src;
>>  
>>  	get_device(dev);
>>  
>> -	ept = rpmsg_create_ept(rpdev, rpmsg_ept_cb, eptdev, eptdev->chinfo);
>> -	if (!ept) {
>> -		dev_err(dev, "failed to open %s\n", eptdev->chinfo.name);
>> -		put_device(dev);
>> -		return -EINVAL;
>> +	/*
>> +	 * The RPMsg device can has been created by a ns announcement. In this
>> +	 * case a default endpoint has been created. Reuse it to avoid to manage
>> +	 * a new address on each open close.
>> +	 */
> 
> Here too it is very difficult to understand because the comment
> doesn't not describe what the code does.  The code creates an enpoint if it
> has not been created, which means /dev/rpmsgX was created from the ioctl. 

Right, not enough explicit

Thanks,
Arnaud

> 
>> +	ept = rpdev->ept;
>> +	if (!ept || addr != ept->addr) {
>> +		ept = rpmsg_create_ept(rpdev, rpmsg_ept_cb, eptdev, eptdev->chinfo);
>> +		if (!ept) {
>> +			dev_err(dev, "failed to open %s\n", eptdev->chinfo.name);
>> +			put_device(dev);
>> +			return -EINVAL;
>> +		}
>>  	}
>>  
>>  	eptdev->ept = ept;
>> @@ -133,12 +142,17 @@ static int rpmsg_eptdev_open(struct inode *inode, struct file *filp)
>>  static int rpmsg_eptdev_release(struct inode *inode, struct file *filp)
>>  {
>>  	struct rpmsg_eptdev *eptdev = cdev_to_eptdev(inode->i_cdev);
>> +	struct rpmsg_device *rpdev = eptdev->rpdev;
>>  	struct device *dev = &eptdev->dev;
>>  
>> -	/* Close the endpoint, if it's not already destroyed by the parent */
>> +	/*
>> +	 * Close the endpoint, if it's not already destroyed by the parent and it is not the
>> +	 * default one.
>> +	 */
>>  	mutex_lock(&eptdev->ept_lock);
>>  	if (eptdev->ept) {
>> -		rpmsg_destroy_ept(eptdev->ept);
>> +		if (eptdev->ept != rpdev->ept)
>> +			rpmsg_destroy_ept(eptdev->ept);
>>  		eptdev->ept = NULL;
>>  	}
>>  	mutex_unlock(&eptdev->ept_lock);
>> -- 
>> 2.17.1
>>