[PATCH v4 2/2] misc: pvpanic: introduce events device attribue

[zhenwei pi]

Suggested by Paolo & Greg, add 'events' device attribute that can be
used to limit which capabilities the driver uses.

Finally, the pvpanic guest driver works by the limitation of both
device capability and user setting.

Signed-off-by: zhenwei pi <pizhenwei@xxxxxxxxxxxxx>
---
 .../ABI/testing/sysfs-bus-pci-devices-pvpanic |  7 +++++
 drivers/misc/pvpanic.c                        | 26 ++++++++++++++++++-
 2 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/Documentation/ABI/testing/sysfs-bus-pci-devices-pvpanic b/Documentation/ABI/testing/sysfs-bus-pci-devices-pvpanic
index 57d014a2c339..4750cfa0af2b 100644
--- a/Documentation/ABI/testing/sysfs-bus-pci-devices-pvpanic
+++ b/Documentation/ABI/testing/sysfs-bus-pci-devices-pvpanic
@@ -5,3 +5,10 @@ Description:
 		Read-only attribute. Capabilities of pvpanic device
 		which are supported by QEMU.
 		Format: %s.
+
+What:          /sys/devices/pci0000:00/*/QEMU0001:00/events
+Date:          Jan 2021
+Contact:       zhenwei pi <pizhenwei@xxxxxxxxxxxxx>
+Description:
+               RW attribute. Set/get which features in-use.
+               Format: %x.
diff --git a/drivers/misc/pvpanic.c b/drivers/misc/pvpanic.c
index c2f6a9e866b3..07a008e15bd2 100644
--- a/drivers/misc/pvpanic.c
+++ b/drivers/misc/pvpanic.c
@@ -19,8 +19,31 @@
 #include <uapi/misc/pvpanic.h>
 
 static void __iomem *base;
+static unsigned int events = PVPANIC_PANICKED | PVPANIC_CRASH_LOADED;
 static unsigned int capability = PVPANIC_PANICKED | PVPANIC_CRASH_LOADED;
 
+static ssize_t events_show(struct device *dev,  struct device_attribute *attr, char *buf)
+{
+	return sprintf(buf, "%x\n", events);
+}
+
+static ssize_t events_store(struct device *dev,  struct device_attribute *attr,
+			    const char *buf, size_t count)
+{
+	unsigned int tmp;
+	int err;
+
+	err = kstrtouint(buf, 16, &tmp);
+	if (err)
+		return err;
+
+	events = tmp;
+
+	return count;
+
+}
+static DEVICE_ATTR_RW(events);
+
 static ssize_t capability_show(struct device *dev,
 			       struct device_attribute *attr, char *buf)
 {
@@ -32,6 +55,7 @@ static DEVICE_ATTR_RO(capability);
 
 static struct attribute *pvpanic_dev_attrs[] = {
 	&dev_attr_capability.attr,
+	&dev_attr_events.attr,
 	NULL
 };
 ATTRIBUTE_GROUPS(pvpanic_dev);
@@ -43,7 +67,7 @@ MODULE_LICENSE("GPL");
 static void
 pvpanic_send_event(unsigned int event)
 {
-	if (event & capability)
+	if (event & capability & events)
 		iowrite8(event, base);
 }
 
-- 
2.25.1