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s390/cio: introduce driver_override on the css bus

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Sometimes, we want to control which of the matching drivers
binds to a subchannel device (e.g. for subchannels we want to
handle via vfio-ccw).

For pci devices, a mechanism to do so has been introduced in
782a985d7a ("PCI: Introduce new device binding path using
pci_dev.driver_override"). It makes sense to introduce the
driver_override attribute for subchannel devices as well, so
that we can easily extend the 'driverctl' tool (which makes
use of the driver_override attribute for pci).

Note that unlike pci we still require a driver override to
match the subchannel type; matching more than one subchannel
type is probably not useful anyway.

Signed-off-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Halil Pasic <pasic@linux.ibm.com>
Reviewed-by: Sebastian Ott <sebott@linux.ibm.com>
Signed-off-by: Sebastian Ott <sebott@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
This commit is contained in:
Cornelia Huck
2019-06-13 13:08:15 +02:00
committed by Vasily Gorbik
parent dbd66558dd
commit ebc3d17915
3 changed files with 77 additions and 0 deletions
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53
drivers/s390/cio/css.c
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@@ -167,6 +167,7 @@ static void css_subchannel_release(struct device *dev)
sch->config.intparm = 0;
cio_commit_config(sch);
kfree(sch->driver_override);
kfree(sch->lock);
kfree(sch);
}
@@ -323,9 +324,57 @@ static ssize_t modalias_show(struct device *dev, struct device_attribute *attr,
static DEVICE_ATTR_RO(modalias);
static ssize_t driver_override_store(struct device *dev,
struct device_attribute *attr,
const char *buf, size_t count)
{
struct subchannel *sch = to_subchannel(dev);
char *driver_override, *old, *cp;
/* We need to keep extra room for a newline */
if (count >= (PAGE_SIZE - 1))
return -EINVAL;
driver_override = kstrndup(buf, count, GFP_KERNEL);
if (!driver_override)
return -ENOMEM;
cp = strchr(driver_override, '\n');
if (cp)
*cp = '\0';
device_lock(dev);
old = sch->driver_override;
if (strlen(driver_override)) {
sch->driver_override = driver_override;
} else {
kfree(driver_override);
sch->driver_override = NULL;
}
device_unlock(dev);
kfree(old);
return count;
}
static ssize_t driver_override_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
struct subchannel *sch = to_subchannel(dev);
ssize_t len;
device_lock(dev);
len = snprintf(buf, PAGE_SIZE, "%s\n", sch->driver_override);
device_unlock(dev);
return len;
}
static DEVICE_ATTR_RW(driver_override);
static struct attribute *subch_attrs[] = {
&dev_attr_type.attr,
&dev_attr_modalias.attr,
&dev_attr_driver_override.attr,
NULL,
};
@@ -1348,6 +1397,10 @@ static int css_bus_match(struct device *dev, struct device_driver *drv)
struct css_driver *driver = to_cssdriver(drv);
struct css_device_id *id;
/* When driver_override is set, only bind to the matching driver */
if (sch->driver_override && strcmp(sch->driver_override, drv->name))
return 0;
for (id = driver->subchannel_type; id->match_flags; id++) {
if (sch->st == id->type)
return 1;