linux-kernel - Re: [PATCH v5 13/16] rpmsg: char: introduce __rpmsg_chrdev_create

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Date:   Fri, 5 Mar 2021 11:01:47 -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 13/16] rpmsg: char: introduce
 __rpmsg_chrdev_create_eptdev function

On Fri, Mar 05, 2021 at 11:46:47AM +0100, Arnaud POULIQUEN wrote:
> 
> 
> On 3/4/21 7:55 PM, Mathieu Poirier wrote:
> > On Fri, Feb 19, 2021 at 12:14:58PM +0100, Arnaud Pouliquen wrote:
> >> Introduce the __rpmsg_chrdev_create_eptdev internal function that returns
> >> the rpmsg_eptdev context structure.
> >> This patch prepares the introduction of a RPMsg device for the
> >> char device. the RPMsg device will need a reference to the context.
> >>
> >> Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@...s.st.com>
> >> ---
> >>  drivers/rpmsg/rpmsg_char.c | 23 ++++++++++++++++++-----
> >>  1 file changed, 18 insertions(+), 5 deletions(-)
> >>
> >> diff --git a/drivers/rpmsg/rpmsg_char.c b/drivers/rpmsg/rpmsg_char.c
> >> index 09ae1304837c..66dcb8845d6c 100644
> >> --- a/drivers/rpmsg/rpmsg_char.c
> >> +++ b/drivers/rpmsg/rpmsg_char.c
> >> @@ -328,8 +328,9 @@ int rpmsg_chrdev_eptdev_destroy(struct device *dev, void *data)
> >>  }
> >>  EXPORT_SYMBOL(rpmsg_chrdev_eptdev_destroy);
> >>  
> >> -int rpmsg_chrdev_create_eptdev(struct rpmsg_device *rpdev, struct device *parent,
> >> -			       struct rpmsg_channel_info chinfo)
> >> +static struct rpmsg_eptdev *__rpmsg_chrdev_create_eptdev(struct rpmsg_device *rpdev,
> >> +							 struct device *parent,
> >> +							 struct rpmsg_channel_info chinfo)
> >>  {
> >>  	struct rpmsg_eptdev *eptdev;
> >>  	struct device *dev;
> >> @@ -337,7 +338,7 @@ int rpmsg_chrdev_create_eptdev(struct rpmsg_device *rpdev, struct device *parent
> >>  
> >>  	eptdev = kzalloc(sizeof(*eptdev), GFP_KERNEL);
> >>  	if (!eptdev)
> >> -		return -ENOMEM;
> >> +		return ERR_PTR(-ENOMEM);
> >>  
> >>  	dev = &eptdev->dev;
> >>  	eptdev->rpdev = rpdev;
> >> @@ -381,7 +382,7 @@ int rpmsg_chrdev_create_eptdev(struct rpmsg_device *rpdev, struct device *parent
> >>  		put_device(dev);
> >>  	}
> >>  
> >> -	return ret;
> >> +	return eptdev;
> >>  
> >>  free_ept_ida:
> >>  	ida_simple_remove(&rpmsg_ept_ida, dev->id);
> >> @@ -391,7 +392,19 @@ int rpmsg_chrdev_create_eptdev(struct rpmsg_device *rpdev, struct device *parent
> >>  	put_device(dev);
> >>  	kfree(eptdev);
> >>  
> >> -	return ret;
> >> +	return ERR_PTR(ret);
> >> +}
> >> +
> >> +int rpmsg_chrdev_create_eptdev(struct rpmsg_device *rpdev, struct device *parent,
> >> +			       struct rpmsg_channel_info chinfo)
> >> +{
> >> +	struct rpmsg_eptdev *eptdev;
> >> +
> >> +	eptdev = __rpmsg_chrdev_create_eptdev(rpdev, &rpdev->dev, chinfo);
> > 
> > Shouldn't the second argument to __rpmsg_chrdev_create_eptdev() be @parent?
> 
> This keep the legacy hierarchy:
> https://elixir.bootlin.com/linux/latest/source/drivers/rpmsg/rpmsg_char.c#L362

In patch 12 it is clear the first and second arguments are ctrldev->rpdev and
ctrldev->dev.  In this set the second arguments becomes rpdev->dev, which is
different than ctrldev->dev.  Goind back to rpmsg_ctrl_probe() we have:

        dev = &ctrldev->dev;
        device_initialize(dev);
        dev->parent = &rpdev->dev;

As such in __rpmsg_chrdev_create_eptdev(), eptdev->dev->parent becomes
ctrldev->dev->parent rather than ctrldev->dev.

> 
> Thanks,
> Arnaud
> 
> 
> > 
> >> +	if (IS_ERR(eptdev))
> >> +		return PTR_ERR(eptdev);
> >> +
> >> +	return 0;
> >>  }
> >>  EXPORT_SYMBOL(rpmsg_chrdev_create_eptdev);
> >>  
> >> -- 
> >> 2.17.1
> >>