Re: [PATCH V3 5/5] virtio: Bind virtio device to device-tree node

[Alexey Kardashevskiy <aik@ozlabs.ru>]

On 13/09/2021 19:45, Michael S. Tsirkin wrote:
> On Mon, Sep 13, 2021 at 07:19:17PM +1000, Alexey Kardashevskiy wrote:
>>
>>
>> On 26/07/2021 14:51, Viresh Kumar wrote:
>>> Bind the virtio devices with their of_node. This will help users of the
>>> virtio devices to mention their dependencies on the device in the DT
>>> itself. Like GPIO pin users can use the phandle of the device node, or
>>> the node may contain more subnodes to add i2c or spi eeproms and other
>>> users.
>>>
>>> Reviewed-by: Arnd Bergmann <arnd@arndb.de>
>>> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
>>> ---
>>>  drivers/virtio/virtio.c | 57 ++++++++++++++++++++++++++++++++++++++---
>>>  1 file changed, 54 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
>>> index 4b15c00c0a0a..d001e84a5b23 100644
>>> --- a/drivers/virtio/virtio.c
>>> +++ b/drivers/virtio/virtio.c
>>> @@ -4,6 +4,7 @@
>>>  #include <linux/virtio_config.h>
>>>  #include <linux/module.h>
>>>  #include <linux/idr.h>
>>> +#include <linux/of.h>
>>>  #include <uapi/linux/virtio_ids.h>
>>>  
>>>  /* Unique numbering for virtio devices. */
>>> @@ -292,6 +293,9 @@ static int virtio_dev_remove(struct device *_d)
>>>  
>>>  	/* Acknowledge the device's existence again. */
>>>  	virtio_add_status(dev, VIRTIO_CONFIG_S_ACKNOWLEDGE);
>>> +
>>> +	of_node_put(dev->dev.of_node);
>>> +
>>>  	return 0;
>>>  }
>>>  
>>> @@ -319,6 +323,43 @@ void unregister_virtio_driver(struct virtio_driver *driver)
>>>  }
>>>  EXPORT_SYMBOL_GPL(unregister_virtio_driver);
>>>  
>>> +static int virtio_device_of_init(struct virtio_device *dev)
>>> +{
>>> +	struct device_node *np, *pnode = dev_of_node(dev->dev.parent);
>>> +	char compat[] = "virtio,XXXXXXXX"; /* Reserve enough space 32-bit id */
>>> +	int ret, count;
>>> +
>>> +	if (!pnode)
>>> +		return 0;
>>> +
>>> +	count = of_get_available_child_count(pnode);
>>> +	if (!count)
>>> +		return 0;
>>> +
>>> +	/* There can be only 1 child node */
>>> +	if (WARN_ON(count > 1))
>>> +		return -EINVAL;
>>> +
>>> +	np = of_get_next_available_child(pnode, NULL);
>>> +	if (WARN_ON(!np))
>>> +		return -ENODEV;
>>> +
>>> +	BUG_ON(snprintf(compat, sizeof(compat), "virtio,%x", dev->id.device) >=
>>> +	       sizeof(compat));
>>> +
>>> +	if (!of_device_is_compatible(np, compat)) {
>>
>>
>> This broke powerpc/pseries as there these virtio devices are PCI so
>> there is no "compat" - PCI vendor id/device ids play role of "compat".
>> Thanks,
> 
> Hmm now that you say this I wonder why do we bother
> with this check, too. When can this be invoked for something
> that is not a virtio device? And is it enough to just
> skip of_node initialization then?


I am not following here, the problem device is virtio-scsi which is
virtio-derived, or you meant that virtio which hosts virtio-bus?

> 
>>
>>
>>
>>> +		ret = -EINVAL;
> 
> 
> So basically ret = 0 above?


Yup, this does fix it. Thanks,

> 
> 
>>> +		goto out;
>>> +	}
>>> +
>>> +	dev->dev.of_node = np;
>>> +	return 0;
>>> +
>>> +out:
>>> +	of_node_put(np);
>>> +	return ret;
>>> +}
>>> +
>>>  /**
>>>   * register_virtio_device - register virtio device
>>>   * @dev        : virtio device to be registered
>>> @@ -343,6 +384,10 @@ int register_virtio_device(struct virtio_device *dev)
>>>  	dev->index = err;
>>>  	dev_set_name(&dev->dev, "virtio%u", dev->index);
>>>  
>>> +	err = virtio_device_of_init(dev);
>>> +	if (err)
>>> +		goto out_ida_remove;
>>> +
>>>  	spin_lock_init(&dev->config_lock);
>>>  	dev->config_enabled = false;
>>>  	dev->config_change_pending = false;
>>> @@ -362,10 +407,16 @@ int register_virtio_device(struct virtio_device *dev)
>>>  	 */
>>>  	err = device_add(&dev->dev);
>>>  	if (err)
>>> -		ida_simple_remove(&virtio_index_ida, dev->index);
>>> +		goto out_of_node_put;
>>> +
>>> +	return 0;
>>> +
>>> +out_of_node_put:
>>> +	of_node_put(dev->dev.of_node);
>>> +out_ida_remove:
>>> +	ida_simple_remove(&virtio_index_ida, dev->index);
>>>  out:
>>> -	if (err)
>>> -		virtio_add_status(dev, VIRTIO_CONFIG_S_FAILED);
>>> +	virtio_add_status(dev, VIRTIO_CONFIG_S_FAILED);
>>>  	return err;
>>>  }
>>>  EXPORT_SYMBOL_GPL(register_virtio_device);
>>>
>>
>> -- 
>> Alexey
> 

-- 
Alexey