Re: [PATCH] vdpa: regist vhost-vdpa dev class

[Stefano Garzarella]

On Thu, Dec 23, 2021 at 03:31:45PM +0800, Yi Wang wrote:
> From: Zhang Min <zhang.min9@xxxxxxxxxx>
>
> Some applications like kata-containers need to acquire MAJOR/MINOR/DEVNAME
> for devInfo [1], so regist vhost-vdpa dev class to expose uevent.
>
> 1. https://github.com/kata-containers/kata-containers/blob/main/src/runtime/virtcontainers/device/config/config.go
>
> Signed-off-by: Zhang Min <zhang.min9@xxxxxxxxxx>
> Signed-off-by: Yi Wang <wang.yi59@xxxxxxxxxx>
> ---
> drivers/vhost/vdpa.c | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
>
> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> index fb41db3da611..90fbad93e7a2 100644
> --- a/drivers/vhost/vdpa.c
> +++ b/drivers/vhost/vdpa.c
> @@ -1012,6 +1012,7 @@ static void vhost_vdpa_release_dev(struct device *device)
> 	kfree(v);
> }
>
> +static struct class *vhost_vdpa_class;
  ^
Maybe is better to move this declaration on top, near `static dev_t 
vhost_vdpa_major;`

> static int vhost_vdpa_probe(struct vdpa_device *vdpa)
> {
> 	const struct vdpa_config_ops *ops = vdpa->config;
> @@ -1040,6 +1041,7 @@ static int vhost_vdpa_probe(struct vdpa_device *vdpa)
> 	v->dev.release = vhost_vdpa_release_dev;
> 	v->dev.parent = &vdpa->dev;
> 	v->dev.devt = MKDEV(MAJOR(vhost_vdpa_major), minor);
> +	v->dev.class = vhost_vdpa_class;
> 	v->vqs = kmalloc_array(v->nvqs, sizeof(struct vhost_virtqueue),
> 			       GFP_KERNEL);
> 	if (!v->vqs) {
> @@ -1097,6 +1099,14 @@ static int __init vhost_vdpa_init(void)
> {
> 	int r;
>
> +	vhost_vdpa_class = class_create(THIS_MODULE, "vhost-vdpa");
> +	if (IS_ERR(vhost_vdpa_class)) {
> +		r = PTR_ERR(vhost_vdpa_class);
> +		pr_warn("vhost vdpa class create error %d,  maybe mod reinserted\n", r);
                                                          ^
double space.

I'm not a native speaker, but I would rephrase the second part to "maybe 
the module is already loaded"

> +		vhost_vdpa_class = NULL;
> +		return r;
> +	}
> +
> 	r = alloc_chrdev_region(&vhost_vdpa_major, 0, VHOST_VDPA_DEV_MAX,
> 				"vhost-vdpa");
> 	if (r)
> @@ -1111,6 +1121,7 @@ static int __init vhost_vdpa_init(void)
> err_vdpa_register_driver:
> 	unregister_chrdev_region(vhost_vdpa_major, VHOST_VDPA_DEV_MAX);
> err_alloc_chrdev:
> +	class_destroy(vhost_vdpa_class);

Should we set `vhost_vdpa_class` to NULL here?

If yes, maybe better to add a new label, and a goto in the 
`class_create` error handling.

> 	return r;
> }
> module_init(vhost_vdpa_init);
> @@ -1118,6 +1129,7 @@ module_init(vhost_vdpa_init);
> static void __exit vhost_vdpa_exit(void)
> {
> 	vdpa_unregister_driver(&vhost_vdpa_driver);
> +	class_destroy(vhost_vdpa_class);

I would move it after unregister_chrdev_region() to have the reverse 
order of initialization (as we already rightly do in the error path of 
vhost_vdpa_init()).

Thanks,
Stefano

> 	unregister_chrdev_region(vhost_vdpa_major, VHOST_VDPA_DEV_MAX);
> }
> module_exit(vhost_vdpa_exit);
> --
> 2.27.0
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