[PATCH v3 1/2] drm: Add GPU reset sysfs event

[André Almeida]

From: Shashank Sharma <shashank.sharma@xxxxxxx>

Add a sysfs event to notify userspace about GPU resets providing:
- PID that triggered the GPU reset, if any. Resets can happen from
  kernel threads as well, in that case no PID is provided
- Information about the reset (e.g. was VRAM lost?)

Co-developed-by: André Almeida <andrealmeid@xxxxxxxxxx>
Signed-off-by: André Almeida <andrealmeid@xxxxxxxxxx>
Signed-off-by: Shashank Sharma <shashank.sharma@xxxxxxx>
---

V3:
   - Reduce information to just PID and flags
   - Use pid pointer instead of just pid number
   - BUG() if no reset info is provided

V2:
   - Addressed review comments from Christian and Amar
   - move the reset information structure to DRM layer
   - drop _ctx from struct name
   - make pid 32 bit(than 64)
   - set flag when VRAM invalid (than valid)
   - add process name as well (Amar)
---
 drivers/gpu/drm/drm_sysfs.c | 26 ++++++++++++++++++++++++++
 include/drm/drm_sysfs.h     | 13 +++++++++++++
 2 files changed, 39 insertions(+)

diff --git a/drivers/gpu/drm/drm_sysfs.c b/drivers/gpu/drm/drm_sysfs.c
index 430e00b16eec..85777abf4194 100644
--- a/drivers/gpu/drm/drm_sysfs.c
+++ b/drivers/gpu/drm/drm_sysfs.c
@@ -409,6 +409,32 @@ void drm_sysfs_hotplug_event(struct drm_device *dev)
 }
 EXPORT_SYMBOL(drm_sysfs_hotplug_event);
 
+/**
+ * drm_sysfs_reset_event - generate a DRM uevent to indicate GPU reset
+ * @dev: DRM device
+ * @reset_info: The contextual information about the reset (like PID, flags)
+ *
+ * Send a uevent for the DRM device specified by @dev. This informs
+ * user that a GPU reset has occurred, so that an interested client
+ * can take any recovery or profiling measure.
+ */
+void drm_sysfs_reset_event(struct drm_device *dev, struct drm_reset_event_info *reset_info)
+{
+	unsigned char pid_str[13];
+	unsigned char flags_str[18];
+	unsigned char reset_str[] = "RESET=1";
+	char *envp[] = { reset_str, pid_str, flags_str, NULL };
+
+	DRM_DEBUG("generating reset event\n");
+
+	BUG_ON(!reset_info);
+
+	snprintf(pid_str, sizeof(pid_str), "PID=%u", pid_vnr(reset_info->pid));
+	snprintf(flags_str, sizeof(flags_str), "FLAGS=0x%llx", reset_info->flags);
+	kobject_uevent_env(&dev->primary->kdev->kobj, KOBJ_CHANGE, envp);
+}
+EXPORT_SYMBOL(drm_sysfs_reset_event);
+
 /**
  * drm_sysfs_connector_hotplug_event - generate a DRM uevent for any connector
  * change
diff --git a/include/drm/drm_sysfs.h b/include/drm/drm_sysfs.h
index 6273cac44e47..dbb0ac6230b8 100644
--- a/include/drm/drm_sysfs.h
+++ b/include/drm/drm_sysfs.h
@@ -2,15 +2,28 @@
 #ifndef _DRM_SYSFS_H_
 #define _DRM_SYSFS_H_
 
+#define DRM_RESET_EVENT_VRAM_LOST (1 << 0)
+
 struct drm_device;
 struct device;
 struct drm_connector;
 struct drm_property;
 
+/**
+ * struct drm_reset_event_info - Information about a GPU reset event
+ * @pid: Process that triggered the reset, if any
+ * @flags: Extra information around the reset event (e.g. is VRAM lost?)
+ */
+struct drm_reset_event_info {
+	struct pid *pid;
+	uint64_t flags;
+};
+
 int drm_class_device_register(struct device *dev);
 void drm_class_device_unregister(struct device *dev);
 
 void drm_sysfs_hotplug_event(struct drm_device *dev);
+void drm_sysfs_reset_event(struct drm_device *dev, struct drm_reset_event_info *reset_info);
 void drm_sysfs_connector_hotplug_event(struct drm_connector *connector);
 void drm_sysfs_connector_status_event(struct drm_connector *connector,
 				      struct drm_property *property);
-- 
2.38.1