Add support for overriding the default matching of a dfl device to a dfl
driver. It follows the same way that can be used for PCI and platform
devices. This patch adds the 'driver_override' sysfs file. It can be
used by VFIO to bind dfl devices for user accessing.
Signed-off-by: Xu Yilun <yilun.xu@xxxxxxxxx>
---
Documentation/ABI/testing/sysfs-bus-dfl | 20 ++++++++++++
drivers/fpga/dfl.c | 54 ++++++++++++++++++++++++++++++++-
include/linux/fpga/dfl-bus.h | 2 ++
3 files changed, 75 insertions(+), 1 deletion(-)
diff --git a/Documentation/ABI/testing/sysfs-bus-dfl b/Documentation/ABI/testing/sysfs-bus-dfl
index 23543be..cf1357a 100644
--- a/Documentation/ABI/testing/sysfs-bus-dfl
+++ b/Documentation/ABI/testing/sysfs-bus-dfl
@@ -13,3 +13,23 @@ Contact: Xu Yilun <yilun.xu@xxxxxxxxx>
Description: Read-only. It returns feature identifier local to its DFL FIU
type.
Format: 0x%x
+
+What: /sys/bus/dfl/devices/.../driver_override
+Date: Sep 2020
+KernelVersion: 5.10
+Contact: Xu Yilun <yilun.xu@xxxxxxxxx>
+Description: This file allows the driver for a device to be specified. When
+ specified, only a driver with a name matching the value written
+ to driver_override will have an opportunity to bind to the
+ device. The override is specified by writing a string to the
+ driver_override file (echo vfio-mdev-dfl > driver_override) and
+ may be cleared with an empty string (echo > driver_override).
+ This returns the device to standard matching rules binding.
+ Writing to driver_override does not automatically unbind the
+ device from its current driver or make any attempt to
+ automatically load the specified driver. If no driver with a
+ matching name is currently loaded in the kernel, the device
+ will not bind to any driver. This also allows devices to
+ opt-out of driver binding using a driver_override name such as
+ "none". Only a single driver may be specified in the override,
+ there is no support for parsing delimiters.
diff --git a/drivers/fpga/dfl.c b/drivers/fpga/dfl.c
index 02a6780..98f88ee 100644
--- a/drivers/fpga/dfl.c
+++ b/drivers/fpga/dfl.c
@@ -262,6 +262,10 @@ static int dfl_bus_match(struct device *dev, struct device_driver *drv)
struct dfl_driver *ddrv = to_dfl_drv(drv);
const struct dfl_device_id *id_entry;
+ /* When driver_override is set, only bind to the matching driver */
+ if (ddev->driver_override)
+ return !strcmp(ddev->driver_override, drv->name);
+
id_entry = ddrv->id_table;
if (id_entry) {
while (id_entry->feature_id) {
@@ -304,6 +308,53 @@ static int dfl_bus_uevent(struct device *dev, struct kobj_uevent_env *env)
ddev->type, ddev->feature_id);
}
+static ssize_t driver_override_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct dfl_device *ddev = to_dfl_dev(dev);
+ ssize_t len;
+
+ device_lock(dev);
+ len = sprintf(buf, "%s\n", ddev->driver_override);
+ device_unlock(dev);
+ return len;
+}
+
+static ssize_t driver_override_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ struct dfl_device *ddev = to_dfl_dev(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 = ddev->driver_override;
+ if (strlen(driver_override)) {
+ ddev->driver_override = driver_override;
+ } else {
+ kfree(driver_override);
+ ddev->driver_override = NULL;
+ }
+ device_unlock(dev);
+
+ kfree(old);
+
+ return count;
+}
+static DEVICE_ATTR_RW(driver_override);
+
static ssize_t
type_show(struct device *dev, struct device_attribute *attr, char *buf)
{
@@ -325,6 +376,7 @@ static DEVICE_ATTR_RO(feature_id);
static struct attribute *dfl_dev_attrs[] = {
&dev_attr_type.attr,
&dev_attr_feature_id.attr,
+ &dev_attr_driver_override.attr,
NULL,
};
ATTRIBUTE_GROUPS(dfl_dev);
@@ -470,7 +522,7 @@ static int dfl_devs_add(struct dfl_feature_platform_data *pdata)
int __dfl_driver_register(struct dfl_driver *dfl_drv, struct module *owner)
{
- if (!dfl_drv || !dfl_drv->probe || !dfl_drv->id_table)
+ if (!dfl_drv || !dfl_drv->probe)
return -EINVAL;
dfl_drv->drv.owner = owner;
diff --git a/include/linux/fpga/dfl-bus.h b/include/linux/fpga/dfl-bus.h
index 2a2b283..09a9ee1 100644
--- a/include/linux/fpga/dfl-bus.h
+++ b/include/linux/fpga/dfl-bus.h
@@ -43,6 +43,8 @@ struct dfl_device {
unsigned int num_irqs;
struct dfl_fpga_cdev *cdev;
const struct dfl_device_id *id_entry;
+
+ char *driver_override;
};
/**
--
2.7.4
