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

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Message-ID: <20210913053816-mutt-send-email-mst@kernel.org>
Date:   Mon, 13 Sep 2021 05:45:37 -0400
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Alexey Kardashevskiy <aik@...abs.ru>
Cc:     Viresh Kumar <viresh.kumar@...aro.org>,
        Jason Wang <jasowang@...hat.com>,
        Rob Herring <robh+dt@...nel.org>,
        Arnd Bergmann <arnd@...nel.org>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        "Enrico Weigelt, metux IT consult" <info@...ux.net>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Arnd Bergmann <arnd@...db.de>, devicetree@...r.kernel.org,
        Bill Mills <bill.mills@...aro.org>,
        linux-kernel@...r.kernel.org,
        virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH V3 5/5] virtio: Bind virtio device to device-tree node

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@...db.de>
> > Signed-off-by: Viresh Kumar <viresh.kumar@...aro.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?


> 
> 
> 
> > +		ret = -EINVAL;


So basically ret = 0 above?


> > +		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