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 10:39:45 -0700
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>,
        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 Fri, Mar 05, 2021 at 12:09:37PM +0100, Arnaud POULIQUEN wrote:
> 
> 
> 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.

I don't think it is a rule but in the past few years the trend has been to
use a capital letter.  I was convinced the documentation had a capital letter
but you have proven that it doesn't so you can ignore this part if you wish.

> 
> [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.

Yes, it would make this patchset quite simple.

> 
> > 
> >>
> >> 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
> >>