netdev - Re: [PATCH V2 3/5] vDPA: introduce vDPA bus

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Message-ID: <cf7abcc9-f8ef-1fe2-248e-9b9028788ade@redhat.com>
Date:   Wed, 12 Feb 2020 15:55:31 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Jason Gunthorpe <jgg@...lanox.com>
Cc:     mst@...hat.com, linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        tiwei.bie@...el.com, maxime.coquelin@...hat.com,
        cunming.liang@...el.com, zhihong.wang@...el.com,
        rob.miller@...adcom.com, xiao.w.wang@...el.com,
        haotian.wang@...ive.com, lingshan.zhu@...el.com,
        eperezma@...hat.com, lulu@...hat.com, parav@...lanox.com,
        kevin.tian@...el.com, stefanha@...hat.com, rdunlap@...radead.org,
        hch@...radead.org, aadam@...hat.com, jiri@...lanox.com,
        shahafs@...lanox.com, hanand@...inx.com, mhabets@...arflare.com
Subject: Re: [PATCH V2 3/5] vDPA: introduce vDPA bus


On 2020/2/11 下午9:47, Jason Gunthorpe wrote:
> On Mon, Feb 10, 2020 at 11:56:06AM +0800, Jason Wang wrote:
>> +/**
>> + * vdpa_register_device - register a vDPA device
>> + * Callers must have a succeed call of vdpa_init_device() before.
>> + * @vdev: the vdpa device to be registered to vDPA bus
>> + *
>> + * Returns an error when fail to add to vDPA bus
>> + */
>> +int vdpa_register_device(struct vdpa_device *vdev)
>> +{
>> +	int err = device_add(&vdev->dev);
>> +
>> +	if (err) {
>> +		put_device(&vdev->dev);
>> +		ida_simple_remove(&vdpa_index_ida, vdev->index);
>> +	}
> This is a very dangerous construction, I've seen it lead to driver
> bugs. Better to require the driver to always do the put_device on
> error unwind


Ok.


>
> The ida_simple_remove should probably be part of the class release
> function to make everything work right


It looks to me bus instead of class is the correct abstraction here 
since the devices share a set of programming interface but not the 
semantics.

Or do you actually mean type here?


>
>> +/**
>> + * vdpa_unregister_driver - unregister a vDPA device driver
>> + * @drv: the vdpa device driver to be unregistered
>> + */
>> +void vdpa_unregister_driver(struct vdpa_driver *drv)
>> +{
>> +	driver_unregister(&drv->driver);
>> +}
>> +EXPORT_SYMBOL_GPL(vdpa_unregister_driver);
>> +
>> +static int vdpa_init(void)
>> +{
>> +	if (bus_register(&vdpa_bus) != 0)
>> +		panic("virtio bus registration failed");
>> +	return 0;
>> +}
> Linus will tell you not to kill the kernel - return the error code and
> propagate it up to the module init function.


Yes, will fix.


>
>> +/**
>> + * vDPA device - representation of a vDPA device
>> + * @dev: underlying device
>> + * @dma_dev: the actual device that is performing DMA
>> + * @config: the configuration ops for this device.
>> + * @index: device index
>> + */
>> +struct vdpa_device {
>> +	struct device dev;
>> +	struct device *dma_dev;
>> +	const struct vdpa_config_ops *config;
>> +	int index;
> unsigned values shuld be unsigned int
>
> Jason


Will fix.

Thanks

>