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Thu, 6 Feb 2020 11:14:29 +0000 (UTC) Received: from gondolin (dhcp-192-195.str.redhat.com [10.33.192.195]) by smtp.corp.redhat.com (Postfix) with ESMTP id 4670910016DA; Thu, 6 Feb 2020 11:14:22 +0000 (UTC) Date: Thu, 6 Feb 2020 12:14:19 +0100 From: Cornelia Huck To: Alex Williamson Cc: kvm@vger.kernel.org, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, dev@dpdk.org, mtosatti@redhat.com, thomas@monjalon.net, bluca@debian.org, jerinjacobk@gmail.com, bruce.richardson@intel.com Subject: Re: [RFC PATCH 1/7] vfio: Include optional device match in vfio_device_ops callbacks Message-ID: <20200206121419.69997326.cohuck@redhat.com> In-Reply-To: <158085754299.9445.4389176548645142886.stgit@gimli.home> References: <158085337582.9445.17682266437583505502.stgit@gimli.home> <158085754299.9445.4389176548645142886.stgit@gimli.home> Organization: Red Hat GmbH MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Tue, 04 Feb 2020 16:05:43 -0700 Alex Williamson wrote: > Allow bus drivers to provide their own callback to match a device to > the user provided string. > > Signed-off-by: Alex Williamson > --- > drivers/vfio/vfio.c | 19 +++++++++++++++---- > include/linux/vfio.h | 3 +++ > 2 files changed, 18 insertions(+), 4 deletions(-) > > diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c > index 388597930b64..dda1726adda8 100644 > --- a/drivers/vfio/vfio.c > +++ b/drivers/vfio/vfio.c > @@ -875,11 +875,22 @@ EXPORT_SYMBOL_GPL(vfio_device_get_from_dev); > static struct vfio_device *vfio_device_get_from_name(struct vfio_group *group, > char *buf) > { > - struct vfio_device *it, *device = NULL; > + struct vfio_device *it, *device = ERR_PTR(-ENODEV); > > mutex_lock(&group->device_lock); > list_for_each_entry(it, &group->device_list, group_next) { > - if (!strcmp(dev_name(it->dev), buf)) { > + int ret; > + > + if (it->ops->match) { > + ret = it->ops->match(it->device_data, buf); > + if (ret < 0 && ret != -ENODEV) { > + device = ERR_PTR(ret); > + break; > + } > + } else > + ret = strcmp(dev_name(it->dev), buf); The asymmetric braces look a bit odd. > + > + if (!ret) { > device = it; > vfio_device_get(device); > break; > @@ -1441,8 +1452,8 @@ static int vfio_group_get_device_fd(struct vfio_group *group, char *buf) > return -EPERM; > > device = vfio_device_get_from_name(group, buf); > - if (!device) > - return -ENODEV; > + if (IS_ERR(device)) > + return PTR_ERR(device); > > ret = device->ops->open(device->device_data); > if (ret) { > diff --git a/include/linux/vfio.h b/include/linux/vfio.h > index e42a711a2800..755e0f0e2900 100644 > --- a/include/linux/vfio.h > +++ b/include/linux/vfio.h > @@ -26,6 +26,8 @@ > * operations documented below > * @mmap: Perform mmap(2) on a region of the device file descriptor > * @request: Request for the bus driver to release the device > + * @match: Optional device name match callback (return: 0 for match, -ENODEV > + * (or >0) for no match and continue, other -errno: no match and stop) I'm wondering about these conventions. If you basically want a tri-state return (match, don't match/continue, don't match/stop), putting -ENODEV and >0 together feels odd. I would rather expect either - < 0 == don't match/stop, 0 == don't match/continue, > 0 == match, or - 0 == match, -ENODEV (or some other defined error) == don't match/continue, all other values == don't match/abort? > */ > struct vfio_device_ops { > char *name; > @@ -39,6 +41,7 @@ struct vfio_device_ops { > unsigned long arg); > int (*mmap)(void *device_data, struct vm_area_struct *vma); > void (*request)(void *device_data, unsigned int count); > + int (*match)(void *device_data, char *buf); > }; > > extern struct iommu_group *vfio_iommu_group_get(struct device *dev); >