[RFC 09/12] drm/i915: Add a char device file interface to capture GuC ukernel logs

[akash.goel@intel.com]

From: Akash Goel <akash.goel@intel.com>

This patch provides a new character device file interface '/dev/dri/guc_log'
for the User to capture the GuC ukernel logs.

Signed-off-by: Akash Goel <akash.goel@intel.com>
---
 drivers/gpu/drm/i915/i915_guc_submission.c | 51 ++++++++++++++++++++++++++++++
 drivers/gpu/drm/i915/intel_guc.h           |  2 ++
 2 files changed, 53 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_guc_submission.c b/drivers/gpu/drm/i915/i915_guc_submission.c
index 149826a..8a79b6d 100644
--- a/drivers/gpu/drm/i915/i915_guc_submission.c
+++ b/drivers/gpu/drm/i915/i915_guc_submission.c
@@ -25,6 +25,7 @@
 #include <linux/circ_buf.h>
 #include <linux/debugfs.h>
 #include <linux/relay.h>
+#include <linux/miscdevice.h>
 #include "i915_drv.h"
 #include "intel_guc.h"
 
@@ -983,6 +984,54 @@ static void guc_create_log_relay_file(struct intel_guc *guc)
 	if (i915.guc_log_level >= 0)
 		gen8_enable_guc_interrupts(dev);
 }
+#else
+static ssize_t guc_log_read(struct file *file, char __user *buf,
+			   size_t len, loff_t *pos)
+{
+	return 0;
+}
+
+static int guc_log_release(struct inode *inode, struct file *file)
+{
+	return 0;
+}
+
+static int guc_log_open(struct inode *inode, struct file *file)
+{
+	struct miscdevice *miscdev = file->private_data;
+	struct intel_guc_log *guc_log =
+		container_of(miscdev, struct intel_guc_log, misc_dev);
+	struct intel_guc *guc =
+		container_of(guc_log, struct intel_guc, log);
+
+	return 0;
+}
+
+static const struct file_operations guc_log_fops = {
+	.owner          = THIS_MODULE,
+	.open           = guc_log_open,
+	.release        = guc_log_release,
+	.read		= guc_log_read,
+	.llseek		= no_llseek,
+};
+
+static void guc_remove_log_device_file(struct intel_guc *guc)
+{
+	misc_deregister(&guc->log.misc_dev);
+}
+
+static void guc_create_log_device_file(struct intel_guc *guc)
+{
+	guc->log.misc_dev.minor = MISC_DYNAMIC_MINOR;
+	guc->log.misc_dev.name = "guc_log";
+	guc->log.misc_dev.nodename = "dri/guc_log";
+	guc->log.misc_dev.fops = &guc_log_fops;
+
+	if (misc_register(&guc->log.misc_dev)) {
+		DRM_ERROR("failed to register misc device for guc logs!\n");
+		return;
+	}
+}
 #endif
 
 static void guc_logging_fini(struct intel_guc *guc)
@@ -991,6 +1040,7 @@ static void guc_logging_fini(struct intel_guc *guc)
         guc_remove_log_relay_file(guc);
 #else
 	if (guc->log.buf_obj) {
+		guc_remove_log_device_file(guc);
 		i915_gem_object_unpin_map(guc->log.buf_obj);
 		drm_gem_object_unreference(&guc->log.buf_obj->base);
 		guc->log.buf_obj = NULL;
@@ -1031,6 +1081,7 @@ static void guc_logging_init(struct intel_guc *guc)
 	}
 
 	guc->log.buf_obj = obj;
+	guc_create_log_device_file(guc);
 
 	/* Enable the flush interrupt, we have a buffer to store GuC logs */
 	if (i915.guc_log_level >= 0)
diff --git a/drivers/gpu/drm/i915/intel_guc.h b/drivers/gpu/drm/i915/intel_guc.h
index bdc3e63..13810d0 100644
--- a/drivers/gpu/drm/i915/intel_guc.h
+++ b/drivers/gpu/drm/i915/intel_guc.h
@@ -127,6 +127,8 @@ struct intel_guc_log {
 	wait_queue_head_t wq;
 	uint64_t first_seq;
 	uint64_t next_seq;
+	/* For Userspace clients to pull logs via /dev/dri/guc_log */
+	struct miscdevice misc_dev;
 };
 
 struct intel_guc {
-- 
1.9.2

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