[PATCH v2 2/7] staging: fsl_-mc: add device binding path 'driver_override'

From: J. German Rivera
Date: Wed May 06 2015 - 17:38:39 EST


From: Bharat Bhushan <bharat.bhushan@xxxxxxxxxxxxx>

This patch is required for vfio-fsl-mc meta driver to successfully bind
layerscape container devices for device passthrough. This patch adds
a mechanism to allow a layerscape device to specify a driver rather than
a layerscape driver provide a device match.

This patch is based on following proposed patches for PCI and platform devices
- https://lkml.org/lkml/2014/4/8/571 :- For Platform devices
- http://lists-archives.com/linux-kernel/28030441-pci-introduce-new-device-binding-path-using-pci_dev-driver_override.html :- For PCI devices

Example to allow a device (dprc.1) to specifically bind
with driver (vfio-fsl-mc):-
- echo vfio-fsl-mc > /sys/bus/fsl-mc/devices/dprc.1/driver_override
- echo dprc.1 > /sys/bus/fsl-mc/drivers/fsl_mc_dprc/unbind
- echo dprc.1 > /sys/bus/fsl-mc/drivers/vfio-fsl-mc/bind

Signed-off-by: J. German Rivera <German.Rivera@xxxxxxxxxxxxx>
Reviewed-by: Stuart Yoder <stuart.yoder@xxxxxxxxxxxxx>
Tested-by: Stuart Yoder <stuart.yoder@xxxxxxxxxxxxx>
---
Changes in v2:
none

drivers/staging/fsl-mc/bus/mc-bus.c | 67 +++++++++++++++++++++++++++++++++++++
drivers/staging/fsl-mc/include/mc.h | 2 ++
2 files changed, 69 insertions(+)

diff --git a/drivers/staging/fsl-mc/bus/mc-bus.c b/drivers/staging/fsl-mc/bus/mc-bus.c
index d51120a..0e9cba8 100644
--- a/drivers/staging/fsl-mc/bus/mc-bus.c
+++ b/drivers/staging/fsl-mc/bus/mc-bus.c
@@ -58,6 +58,12 @@ static int fsl_mc_bus_match(struct device *dev, struct device_driver *drv)
if (WARN_ON(!fsl_mc_bus_type.dev_root))
goto out;

+ /* When driver_override is set, only bind to the matching driver */
+ if (mc_dev->driver_override) {
+ found = !strcmp(mc_dev->driver_override, mc_drv->driver.name);
+ goto out;
+ }
+
if (!mc_drv->match_id_table)
goto out;

@@ -116,10 +122,69 @@ static int fsl_mc_bus_uevent(struct device *dev, struct kobj_uevent_env *env)
return 0;
}

+static ssize_t driver_override_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ struct fsl_mc_device *mc_dev = to_fsl_mc_device(dev);
+ const char *driver_override, *old = mc_dev->driver_override;
+ char *cp;
+
+ if (WARN_ON(dev->bus != &fsl_mc_bus_type))
+ return -EINVAL;
+
+ if (count > PATH_MAX)
+ return -EINVAL;
+
+ driver_override = kstrndup(buf, count, GFP_KERNEL);
+ if (!driver_override)
+ return -ENOMEM;
+
+ cp = strchr(driver_override, '\n');
+ if (cp)
+ *cp = '\0';
+
+ if (strlen(driver_override)) {
+ mc_dev->driver_override = driver_override;
+ } else {
+ kfree(driver_override);
+ mc_dev->driver_override = NULL;
+ }
+
+ kfree(old);
+
+ return count;
+}
+
+static ssize_t driver_override_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct fsl_mc_device *mc_dev = to_fsl_mc_device(dev);
+
+ return sprintf(buf, "%s\n", mc_dev->driver_override);
+}
+
+static DEVICE_ATTR_RW(driver_override);
+
+static struct attribute *fsl_mc_dev_attrs[] = {
+ &dev_attr_driver_override.attr,
+ NULL,
+};
+
+static const struct attribute_group fsl_mc_dev_group = {
+ .attrs = fsl_mc_dev_attrs,
+};
+
+static const struct attribute_group *fsl_mc_dev_groups[] = {
+ &fsl_mc_dev_group,
+ NULL,
+};
+
struct bus_type fsl_mc_bus_type = {
.name = "fsl-mc",
.match = fsl_mc_bus_match,
.uevent = fsl_mc_bus_uevent,
+ .dev_groups = fsl_mc_dev_groups,
};
EXPORT_SYMBOL_GPL(fsl_mc_bus_type);

@@ -499,6 +564,8 @@ void fsl_mc_device_remove(struct fsl_mc_device *mc_dev)
fsl_mc_bus_type.dev_root = NULL;
}

+ kfree(mc_dev->driver_override);
+ mc_dev->driver_override = NULL;
if (!mc_bus)
kmem_cache_free(mc_dev_cache, mc_dev);
else
diff --git a/drivers/staging/fsl-mc/include/mc.h b/drivers/staging/fsl-mc/include/mc.h
index 531cb8c..f965c4d 100644
--- a/drivers/staging/fsl-mc/include/mc.h
+++ b/drivers/staging/fsl-mc/include/mc.h
@@ -145,6 +145,7 @@ struct fsl_mc_device_irq {
* @regions: pointer to array of MMIO region entries
* @irqs: pointer to array of pointers to interrupts allocated to this device
* @resource: generic resource associated with this MC object device, if any.
+ * @driver_override: Driver name to force a match
*
* Generic device object for MC object devices that are "attached" to a
* MC bus.
@@ -177,6 +178,7 @@ struct fsl_mc_device {
struct resource *regions;
struct fsl_mc_device_irq **irqs;
struct fsl_mc_resource *resource;
+ const char *driver_override;
};

#define to_fsl_mc_device(_dev) \
--
2.3.3

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