[RFC PATCH 2/2] i915: POC use dynamic_debug_exec_queries to control pr_debugs in gvt

[Jim Cromie]

The gvt component of this driver has ~120 pr_debugs, in 9 "classes".
Following model of drm.debug, add a parameter to map bits to these
classes.

In Makefile, add DYNAMIC_DEBUG_MODULE.  This converts gvt's pr_debugs,
even if the rest of drm is not using CONFIG_DRM_USE_DYNAMIC_DEBUG.

Signed-off-by: Jim Cromie <jim.cromie@xxxxxxxxx>
---
 drivers/gpu/drm/i915/gvt/Makefile  |  1 +
 drivers/gpu/drm/i915/i915_params.c | 74 ++++++++++++++++++++++++++++++
 2 files changed, 75 insertions(+)

diff --git a/drivers/gpu/drm/i915/gvt/Makefile b/drivers/gpu/drm/i915/gvt/Makefile
index ea8324abc784..e38a1eb618bd 100644
--- a/drivers/gpu/drm/i915/gvt/Makefile
+++ b/drivers/gpu/drm/i915/gvt/Makefile
@@ -6,4 +6,5 @@ GVT_SOURCE := gvt.o aperture_gm.o handlers.o vgpu.o trace_points.o firmware.o \
 	fb_decoder.o dmabuf.o page_track.o
 
 ccflags-y				+= -I $(srctree)/$(src) -I $(srctree)/$(src)/$(GVT_DIR)/
+ccflags-y				+= -DDYNAMIC_DEBUG_MODULE
 i915-y					+= $(addprefix $(GVT_DIR)/, $(GVT_SOURCE))
diff --git a/drivers/gpu/drm/i915/i915_params.c b/drivers/gpu/drm/i915/i915_params.c
index 7f139ea4a90b..ecc825558e00 100644
--- a/drivers/gpu/drm/i915/i915_params.c
+++ b/drivers/gpu/drm/i915/i915_params.c
@@ -260,3 +260,77 @@ void i915_params_free(struct i915_params *params)
 	I915_PARAMS_FOR_EACH(FREE);
 #undef FREE
 }
+
+/* POC for callback -> dynamic_debug_exec_queries */
+unsigned long __gvt_debug;
+EXPORT_SYMBOL(__gvt_debug);
+
+static char *format_prefix_classes[] = {
+	"gvt: cmd: ",
+	"gvt: core: ",
+	"gvt: dpy: ",
+	"gvt: el: ",
+	"gvt: irq: ",
+	"gvt: mm: ",
+	"gvt: mmio: ",
+	"gvt: render: ",
+	"gvt: sched: "
+};
+#define NUM_CLASSES	ARRAY_SIZE(format_prefix_classes)
+#define OUR_QUERY_SIZE	128 /* we need about 20 */
+
+#include <linux/module.h>
+
+static int param_set_dyndbg(const char *instr, const struct kernel_param *kp)
+{
+	unsigned int val;
+	unsigned long changes, result;
+	int rc, chgct = 0, totct = 0, bitpos;
+	char query[OUR_QUERY_SIZE];
+
+	rc = kstrtouint(instr, 0, &val);
+	if (rc) {
+		pr_err("set_dyndbg: failed\n");
+		return -EINVAL;
+	}
+	result = val;
+	pr_info("set_dyndbg: result:0x%lx from %s\n", result, instr);
+
+	changes = result ^ __gvt_debug;
+
+	for_each_set_bit(bitpos, &changes, NUM_CLASSES) {
+
+		sprintf(query, "format '^%s' %cp", format_prefix_classes[bitpos],
+			test_bit(bitpos, &result) ? '+' : '-');
+
+		chgct = dynamic_debug_exec_queries(query, "i915");
+
+		pr_info("%d changes on: %s\n", chgct, query);
+		totct += chgct;
+	}
+	pr_info("total changes: %d\n", totct);
+	__gvt_debug = result;
+	return 0;
+}
+static int param_get_dyndbg(char *buffer, const struct kernel_param *kp)
+{
+	return scnprintf(buffer, PAGE_SIZE, "%u\n",
+			 *((unsigned int *)kp->arg));
+}
+static const struct kernel_param_ops param_ops_dyndbg = {
+	.set = param_set_dyndbg,
+	.get = param_get_dyndbg,
+};
+
+MODULE_PARM_DESC(debug_gvt, " gvt debug categories:"
+		 "\n\t0x1\t gvt: cmd:"
+		 "\n\t0x2\t gvt: core:"
+		 "\n\t0x4\t gvt: dpy:"
+		 "\n\t0x8\t gvt: el:"
+		 "\n\t0x10\t gvt: irq:"
+		 "\n\t0x20\t gvt: mm:"
+		 "\n\t0x40\t gvt: mmio:"
+		 "\n\t0x80\t gvt: render:"
+		 "\n\t0x100\t gvt: sched:" "\n");
+
+module_param_cb(debug_gvt, &param_ops_dyndbg, &__gvt_debug, 0644);
-- 
2.28.0