diff mbox series

[net-next,09/19] vfio/mdev: Expose mdev alias in sysfs tree

Message ID 20191107160834.21087-9-parav@mellanox.com (mailing list archive)
State New, archived
Headers show
Series Mellanox, mlx5 sub function support | expand

Commit Message

Parav Pandit Nov. 7, 2019, 4:08 p.m. UTC 
Expose the optional alias for an mdev device as a sysfs attribute.
This way, userspace tools such as udev may make use of the alias, for
example to create a netdevice name for the mdev.

Updated documentation for optional read only sysfs attribute.

Reviewed-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: Parav Pandit <parav@mellanox.com>
---
 Documentation/driver-api/vfio-mediated-device.rst |  9 +++++++++
 drivers/vfio/mdev/mdev_sysfs.c                    | 13 +++++++++++++
 2 files changed, 22 insertions(+)

Comments

Jiri Pirko Nov. 8, 2019, 1:22 p.m. UTC | #1 
Thu, Nov 07, 2019 at 05:08:24PM CET, parav@mellanox.com wrote:

[...]

> 
>+static ssize_t alias_show(struct device *device,
>+			  struct device_attribute *attr, char *buf)
>+{
>+	struct mdev_device *dev = mdev_from_dev(device);
>+
>+	if (!dev->alias)
>+		return -EOPNOTSUPP;
>+
>+	return sprintf(buf, "%s\n", dev->alias);
>+}
>+static DEVICE_ATTR_RO(alias);

I wonder, rather than adding another sysfs file, why the alias can't be
simply a symlink to the aliased mdev directory?


>+
> static const struct attribute *mdev_device_attrs[] = {
>+	&dev_attr_alias.attr,
> 	&dev_attr_remove.attr,
> 	NULL,
> };
>-- 
>2.19.2
>
Alex Williamson Nov. 8, 2019, 6:03 p.m. UTC | #2 
On Fri, 8 Nov 2019 14:22:30 +0100
Jiri Pirko <jiri@resnulli.us> wrote:

> Thu, Nov 07, 2019 at 05:08:24PM CET, parav@mellanox.com wrote:
> 
> [...]
> 
> > 
> >+static ssize_t alias_show(struct device *device,
> >+			  struct device_attribute *attr, char *buf)
> >+{
> >+	struct mdev_device *dev = mdev_from_dev(device);
> >+
> >+	if (!dev->alias)
> >+		return -EOPNOTSUPP;
> >+
> >+	return sprintf(buf, "%s\n", dev->alias);
> >+}
> >+static DEVICE_ATTR_RO(alias);  
> 
> I wonder, rather than adding another sysfs file, why the alias can't be
> simply a symlink to the aliased mdev directory?

The user doesn't know the alias in advance, it seems problematic to
assume an arbitrarily named link is the alias.  Thanks,

Alex

> >+
> > static const struct attribute *mdev_device_attrs[] = {
> >+	&dev_attr_alias.attr,
> > 	&dev_attr_remove.attr,
> > 	NULL,
> > };
> >-- 
> >2.19.2
> >
Jiri Pirko Nov. 8, 2019, 6:16 p.m. UTC | #3 
Fri, Nov 08, 2019 at 07:03:55PM CET, alex.williamson@redhat.com wrote:
>On Fri, 8 Nov 2019 14:22:30 +0100
>Jiri Pirko <jiri@resnulli.us> wrote:
>
>> Thu, Nov 07, 2019 at 05:08:24PM CET, parav@mellanox.com wrote:
>> 
>> [...]
>> 
>> > 
>> >+static ssize_t alias_show(struct device *device,
>> >+			  struct device_attribute *attr, char *buf)
>> >+{
>> >+	struct mdev_device *dev = mdev_from_dev(device);
>> >+
>> >+	if (!dev->alias)
>> >+		return -EOPNOTSUPP;
>> >+
>> >+	return sprintf(buf, "%s\n", dev->alias);
>> >+}
>> >+static DEVICE_ATTR_RO(alias);  
>> 
>> I wonder, rather than adding another sysfs file, why the alias can't be
>> simply a symlink to the aliased mdev directory?
>
>The user doesn't know the alias in advance, it seems problematic to
>assume an arbitrarily named link is the alias.  Thanks,

Why the user have to know in advance?


>
>Alex
>
>> >+
>> > static const struct attribute *mdev_device_attrs[] = {
>> >+	&dev_attr_alias.attr,
>> > 	&dev_attr_remove.attr,
>> > 	NULL,
>> > };
>> >-- 
>> >2.19.2
>> >  
>
diff mbox series

Patch

diff --git a/Documentation/driver-api/vfio-mediated-device.rst b/Documentation/driver-api/vfio-mediated-device.rst
index 25eb7d5b834b..7d6d87102f64 100644
--- a/Documentation/driver-api/vfio-mediated-device.rst
+++ b/Documentation/driver-api/vfio-mediated-device.rst
@@ -270,6 +270,7 @@  Directories and Files Under the sysfs for Each mdev Device
          |--- remove
          |--- mdev_type {link to its type}
          |--- vendor-specific-attributes [optional]
+         |--- alias
 
 * remove (write only)
 
@@ -281,6 +282,14 @@  Example::
 
 	# echo 1 > /sys/bus/mdev/devices/$mdev_UUID/remove
 
+* alias (read only, optional)
+Whenever a parent requested to generate an alias, each mdev device of that
+parent is assigned a unique alias by the mdev core.
+This file shows the alias of the mdev device.
+
+Reading this file either returns a valid alias when assigned or returns the
+error code -EOPNOTSUPP when unsupported.
+
 Mediated device Hot plug
 ------------------------
 
diff --git a/drivers/vfio/mdev/mdev_sysfs.c b/drivers/vfio/mdev/mdev_sysfs.c
index 43afe0e80b76..59f4e3cc5233 100644
--- a/drivers/vfio/mdev/mdev_sysfs.c
+++ b/drivers/vfio/mdev/mdev_sysfs.c
@@ -246,7 +246,20 @@  static ssize_t remove_store(struct device *dev, struct device_attribute *attr,
 
 static DEVICE_ATTR_WO(remove);
 
+static ssize_t alias_show(struct device *device,
+			  struct device_attribute *attr, char *buf)
+{
+	struct mdev_device *dev = mdev_from_dev(device);
+
+	if (!dev->alias)
+		return -EOPNOTSUPP;
+
+	return sprintf(buf, "%s\n", dev->alias);
+}
+static DEVICE_ATTR_RO(alias);
+
 static const struct attribute *mdev_device_attrs[] = {
+	&dev_attr_alias.attr,
 	&dev_attr_remove.attr,
 	NULL,
 };