[RFC PATCH v2 4/4] i915: map gvt pr_debug categories to bits in parameters/debug_gvt

[Jim Cromie <jim.cromie@xxxxxxxxx>]

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

If CONFIG_DRM_USE_DYNAMIC_DEBUG=y (and CONFIG_DYNAMIC_DEBUG_CORE), add
-DDYNAMIC_DEBUG_MODULE into Makefile.  TBD: maybe add a separate
CONFIG_I915_USE_DYNAMIC_DEBUG to more fully optionalize this.

In i915_params.c, add callback to map bits to queries.

TBD: the callback code should probably be moved to lib/dynamic_debug,
and given a declarative interface, with implied bit-numbering,
something like:

MOD_PARM_BITMAP_DESC(__gvt_debug,
	"gvt: cmd: ",  "command processing"
	"gvt: core: ", "core help",
	"gvt: dpy: ",  "display help",
	"gvt: el: ",   "help",
	"gvt: irq: ",  "help",
	"gvt: mm: ",   "help",
	"gvt: mmio: ", "help",
	"gvt: render: ", "help",
	"gvt: sched: " "help");
---
 drivers/gpu/drm/i915/gvt/Makefile  |  4 ++
 drivers/gpu/drm/i915/i915_params.c | 76 ++++++++++++++++++++++++++++++
 2 files changed, 80 insertions(+)

diff --git a/drivers/gpu/drm/i915/gvt/Makefile b/drivers/gpu/drm/i915/gvt/Makefile
index ea8324abc784..846ba73b8de6 100644
--- a/drivers/gpu/drm/i915/gvt/Makefile
+++ b/drivers/gpu/drm/i915/gvt/Makefile
@@ -7,3 +7,7 @@ GVT_SOURCE := gvt.o aperture_gm.o handlers.o vgpu.o trace_points.o firmware.o \
 
 ccflags-y				+= -I $(srctree)/$(src) -I $(srctree)/$(src)/$(GVT_DIR)/
 i915-y					+= $(addprefix $(GVT_DIR)/, $(GVT_SOURCE))
+
+#ifdef CONFIG_DRM_USE_DYNAMIC_DEBUG
+ccflags-y	+= -DDYNAMIC_DEBUG_MODULE
+#endif
diff --git a/drivers/gpu/drm/i915/i915_params.c b/drivers/gpu/drm/i915/i915_params.c
index e07f4cfea63a..e0d13aff5274 100644
--- a/drivers/gpu/drm/i915/i915_params.c
+++ b/drivers/gpu/drm/i915/i915_params.c
@@ -265,3 +265,79 @@ 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,
+};
+
+#define info_ln(hexi, prefix) "\n\t0x" __stringify(hexi) "\t" prefix
+
+MODULE_PARM_DESC(debug_gvt, " gvt debug categories:"
+		 info_ln(1, "gvt: cmd:")
+		 info_ln(2, "gvt: core:")
+		 info_ln(4, "gvt: dpy:")
+		 info_ln(8, "gvt: el:")
+		 info_ln(10, "gvt: irq:")
+		 info_ln(20, "gvt: mm:")
+		 info_ln(40, "gvt: mmio:")
+		 info_ln(80, "gvt: render:")
+		 info_ln(100, "gvt: sched:"));
+
+module_param_cb(debug_gvt, &param_ops_dyndbg, &__gvt_debug, 0644);
-- 
2.31.1