linux-kernel - Re: [PATCH] virtio-pci: add softlinks between virtio and pci

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Message-ID: <20110105200501.GA3224@redhat.com>
Date:	Wed, 5 Jan 2011 22:05:02 +0200
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Anthony Liguori <anthony@...emonkey.ws>
Cc:	Rusty Russell <rusty@...tcorp.com.au>,
	Jamie Lokier <jamie@...reable.org>,
	Thomas Weber <swirl@....li>, gleb@...hat.com,
	virtualization@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] virtio-pci: add softlinks between virtio and pci

On Wed, Jan 05, 2011 at 01:28:34PM -0600, Anthony Liguori wrote:
> On 01/05/2011 01:17 PM, Michael S. Tsirkin wrote:
> >We sometimes need to map between the virtio device and
> >the given pci device. One such use is OS installer that
> >gets the boot pci device from BIOS and needs to
> >find the relevant block device. Since it can't,
> >installation fails.
> 
> I have no objection to this patch but I'm a tad confused by the description.
> 
> I assume you mean the installer is querying the boot device via
> int13 get driver parameters such that it returns the pci address of
> the device?
> 
> Or is it querying geometry information and then trying to find the
> best match block device?
> 
> If it's the former, I don't really understand the need for a
> backlink since the PCI address gives you a link to the block device.
> OTOH, if it's the later, it would make sense but then your
> description doesn't really make much sense.
> 
> At any rate, a better commit message would be helpful in explaining
> the need for this.
> 
> Regards,
> 
> Anthony Liguori

OK just to clarify: we get pci address from BIOS
and need the virtio device to get at the linux device
(e.g. block) in the end.  Thus the link from pci to virtio.
I also added a backlink since I thought it's handy.

Does this answer the questions?

Rusty rewrites my commit logs anyway, he has better style :)

> >Supply softlinks between these to make it possible.
> >
> >Signed-off-by: Michael S. Tsirkin<mst@...hat.com>
> >---
> >
> >Gleb, could you please ack that this patch below
> >will be enough to fix the installer issue that
> >you see?
> >
> >  drivers/virtio/virtio_pci.c |   18 +++++++++++++++++-
> >  1 files changed, 17 insertions(+), 1 deletions(-)
> >
> >diff --git a/drivers/virtio/virtio_pci.c b/drivers/virtio/virtio_pci.c
> >index ef8d9d5..06eb2f8 100644
> >--- a/drivers/virtio/virtio_pci.c
> >+++ b/drivers/virtio/virtio_pci.c
> >@@ -25,6 +25,7 @@
> >  #include<linux/virtio_pci.h>
> >  #include<linux/highmem.h>
> >  #include<linux/spinlock.h>
> >+#include<linux/sysfs.h>
> >
> >  MODULE_AUTHOR("Anthony Liguori<aliguori@...ibm.com>");
> >  MODULE_DESCRIPTION("virtio-pci");
> >@@ -667,8 +668,21 @@ static int __devinit virtio_pci_probe(struct pci_dev *pci_dev,
> >  	if (err)
> >  		goto out_set_drvdata;
> >
> >-	return 0;
> >+	err = sysfs_create_link(&pci_dev->dev.kobj,&vp_dev->vdev.dev.kobj,
> >+				"virtio_device");
> >+	if (err)
> >+		goto out_register_device;
> >+
> >+	err = sysfs_create_link(&vp_dev->vdev.dev.kobj,&pci_dev->dev.kobj,
> >+				"bus_device");
> >+	if (err)
> >+		goto out_create_link;
> >
> >+	return 0;
> >+out_create_link:
> >+	sysfs_remove_link(&pci_dev->dev.kobj, "virtio_device");
> >+out_register_device:
> >+	unregister_virtio_device(&vp_dev->vdev);
> >  out_set_drvdata:
> >  	pci_set_drvdata(pci_dev, NULL);
> >  	pci_iounmap(pci_dev, vp_dev->ioaddr);
> >@@ -685,6 +699,8 @@ static void __devexit virtio_pci_remove(struct pci_dev *pci_dev)
> >  {
> >  	struct virtio_pci_device *vp_dev = pci_get_drvdata(pci_dev);
> >
> >+	sysfs_remove_link(&vp_dev->vdev.dev.kobj, "bus_device");
> >+	sysfs_remove_link(&pci_dev->dev.kobj, "virtio_device");
> >  	unregister_virtio_device(&vp_dev->vdev);
> >  }
> >
--
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