drm/i915/params: add i915 parameters to debugfs

Add a debugfs subdirectory i915_params with all the i915 module
parameters. This is a first step, with lots of boilerplate, and not much
benefit yet.

This will result in a new device specific debugfs directory at
/sys/kernel/debug/dri/<N>/i915_params duplicating the module specific
sysfs directory at /sys/module/i915/parameters/. Going forward, all
users of the parameters should use the debugfs, with the module
parameters being phased out.

Add debugfs permissions to I915_PARAMS_FOR_EACH(). This duplicates the
mode with module parameter sysfs, but the goal is to make the module
parameters read-only initial values for device specific parameters.

0 mode will bypass debugfs creation. Use it for verbose_state_checks
which will need special attention in follow-up work.
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/600101c8433e7caf9303663fc85a9972fa1f05e7.1575560168.git.jani.nikula@intel.com

drivers/gpu/drm/i915/Makefile

@@ -66,7 +66,10 @@ i915-y += \
 	i915_user_extensions.o
 
 i915-$(CONFIG_COMPAT)   += i915_ioc32.o
-i915-$(CONFIG_DEBUG_FS) += i915_debugfs.o display/intel_pipe_crc.o
+i915-$(CONFIG_DEBUG_FS) += \
+	i915_debugfs.o \
+	i915_debugfs_params.o \
+	display/intel_pipe_crc.o
 i915-$(CONFIG_PERF_EVENTS) += i915_pmu.o
 
 # "Graphics Technology" (aka we talk to the gpu)

drivers/gpu/drm/i915/i915_debugfs.c

@@ -48,6 +48,7 @@
 #include "gt/uc/intel_guc_submission.h"
 
 #include "i915_debugfs.h"
+#include "i915_debugfs_params.h"
 #include "i915_irq.h"
 #include "i915_trace.h"
 #include "intel_csr.h"
@@ -4311,9 +4312,10 @@ int i915_debugfs_register(struct drm_i915_private *dev_priv)
 	struct drm_minor *minor = dev_priv->drm.primary;
 	int i;
 
+	i915_debugfs_params(dev_priv);
+
 	debugfs_create_file("i915_forcewake_user", S_IRUSR, minor->debugfs_root,
 			    to_i915(minor->dev), &i915_forcewake_fops);
-
 	for (i = 0; i < ARRAY_SIZE(i915_debugfs_files); i++) {
 		debugfs_create_file(i915_debugfs_files[i].name,
 				    S_IRUGO | S_IWUSR,

drivers/gpu/drm/i915/i915_debugfs_params.c

+// SPDX-License-Identifier: MIT
+/*
+ * Copyright © 2019 Intel Corporation
+ */
+
+#include <linux/kernel.h>
+
+#include "i915_drv.h"
+#include "i915_params.h"
+
+/* int param */
+static int i915_param_int_show(struct seq_file *m, void *data)
+{
+	int *value = m->private;
+
+	seq_printf(m, "%d\n", *value);
+
+	return 0;
+}
+
+static int i915_param_int_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, i915_param_int_show, inode->i_private);
+}
+
+static ssize_t i915_param_int_write(struct file *file,
+				    const char __user *ubuf, size_t len,
+				    loff_t *offp)
+{
+	struct seq_file *m = file->private_data;
+	int *value = m->private;
+	int ret;
+
+	ret = kstrtoint_from_user(ubuf, len, 0, value);
+
+	return ret ?: len;
+}
+
+static const struct file_operations i915_param_int_fops = {
+	.owner = THIS_MODULE,
+	.open = i915_param_int_open,
+	.read = seq_read,
+	.write = i915_param_int_write,
+	.llseek = default_llseek,
+	.release = single_release,
+};
+
+static const struct file_operations i915_param_int_fops_ro = {
+	.owner = THIS_MODULE,
+	.open = i915_param_int_open,
+	.read = seq_read,
+	.llseek = default_llseek,
+	.release = single_release,
+};
+
+/* unsigned int param */
+static int i915_param_uint_show(struct seq_file *m, void *data)
+{
+	unsigned int *value = m->private;
+
+	seq_printf(m, "%u\n", *value);
+
+	return 0;
+}
+
+static int i915_param_uint_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, i915_param_uint_show, inode->i_private);
+}
+
+static ssize_t i915_param_uint_write(struct file *file,
+				     const char __user *ubuf, size_t len,
+				     loff_t *offp)
+{
+	struct seq_file *m = file->private_data;
+	unsigned int *value = m->private;
+	int ret;
+
+	ret = kstrtouint_from_user(ubuf, len, 0, value);
+
+	return ret ?: len;
+}
+
+static const struct file_operations i915_param_uint_fops = {
+	.owner = THIS_MODULE,
+	.open = i915_param_uint_open,
+	.read = seq_read,
+	.write = i915_param_uint_write,
+	.llseek = default_llseek,
+	.release = single_release,
+};
+
+static const struct file_operations i915_param_uint_fops_ro = {
+	.owner = THIS_MODULE,
+	.open = i915_param_uint_open,
+	.read = seq_read,
+	.llseek = default_llseek,
+	.release = single_release,
+};
+
+/* char * param */
+static int i915_param_charp_show(struct seq_file *m, void *data)
+{
+	const char **s = m->private;
+
+	seq_printf(m, "%s\n", *s);
+
+	return 0;
+}
+
+static int i915_param_charp_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, i915_param_charp_show, inode->i_private);
+}
+
+static ssize_t i915_param_charp_write(struct file *file,
+				      const char __user *ubuf, size_t len,
+				      loff_t *offp)
+{
+	struct seq_file *m = file->private_data;
+	char **s = m->private;
+	char *new, *old;
+
+	/* FIXME: remove locking after params aren't the module params */
+	kernel_param_lock(THIS_MODULE);
+
+	old = *s;
+	new = strndup_user(ubuf, PAGE_SIZE);
+	if (IS_ERR(new)) {
+		len = PTR_ERR(new);
+		goto out;
+	}
+
+	*s = new;
+
+	kfree(old);
+out:
+	kernel_param_unlock(THIS_MODULE);
+
+	return len;
+}
+
+static const struct file_operations i915_param_charp_fops = {
+	.owner = THIS_MODULE,
+	.open = i915_param_charp_open,
+	.read = seq_read,
+	.write = i915_param_charp_write,
+	.llseek = default_llseek,
+	.release = single_release,
+};
+
+static const struct file_operations i915_param_charp_fops_ro = {
+	.owner = THIS_MODULE,
+	.open = i915_param_charp_open,
+	.read = seq_read,
+	.llseek = default_llseek,
+	.release = single_release,
+};
+
+#define RO(mode) (((mode) & 0222) == 0)
+
+static struct dentry *
+i915_debugfs_create_int(const char *name, umode_t mode,
+			struct dentry *parent, int *value)
+{
+	return debugfs_create_file_unsafe(name, mode, parent, value,
+					  RO(mode) ? &i915_param_int_fops_ro :
+					  &i915_param_int_fops);
+}
+
+static struct dentry *
+i915_debugfs_create_uint(const char *name, umode_t mode,
+			 struct dentry *parent, unsigned int *value)
+{
+	return debugfs_create_file_unsafe(name, mode, parent, value,
+					  RO(mode) ? &i915_param_uint_fops_ro :
+					  &i915_param_uint_fops);
+}
+
+static struct dentry *
+i915_debugfs_create_charp(const char *name, umode_t mode,
+			  struct dentry *parent, char **value)
+{
+	return debugfs_create_file(name, mode, parent, value,
+				   RO(mode) ? &i915_param_charp_fops_ro :
+				   &i915_param_charp_fops);
+}
+
+static __always_inline void
+_i915_param_create_file(struct dentry *parent, const char *name,
+			const char *type, int mode, void *value)
+{
+	if (!mode)
+		return;
+
+	if (!__builtin_strcmp(type, "bool"))
+		debugfs_create_bool(name, mode, parent, value);
+	else if (!__builtin_strcmp(type, "int"))
+		i915_debugfs_create_int(name, mode, parent, value);
+	else if (!__builtin_strcmp(type, "unsigned int"))
+		i915_debugfs_create_uint(name, mode, parent, value);
+	else if (!__builtin_strcmp(type, "unsigned long"))
+		debugfs_create_ulong(name, mode, parent, value);
+	else if (!__builtin_strcmp(type, "char *"))
+		i915_debugfs_create_charp(name, mode, parent, value);
+	else
+		WARN(1, "no debugfs fops defined for param type %s (i915.%s)\n",
+		     type, name);
+}
+
+/* add a subdirectory with files for each i915 param */
+struct dentry *i915_debugfs_params(struct drm_i915_private *i915)
+{
+	struct drm_minor *minor = i915->drm.primary;
+	struct i915_params *params = &i915_modparams;
+	struct dentry *dir;
+
+	dir = debugfs_create_dir("i915_params", minor->debugfs_root);
+	if (IS_ERR(dir))
+		return dir;
+
+	/*
+	 * Note: We could create files for params needing special handling
+	 * here. Set mode in params to 0 to skip the generic create file, or
+	 * just let the generic create file fail silently with -EEXIST.
+	 */
+
+#define REGISTER(T, x, unused, mode, ...) _i915_param_create_file(dir, #x, #T, mode, &params->x);
+	I915_PARAMS_FOR_EACH(REGISTER);
+#undef REGISTER
+
+	return dir;
+}

drivers/gpu/drm/i915/i915_debugfs_params.h

+/* SPDX-License-Identifier: MIT */
+/*
+ * Copyright © 2019 Intel Corporation
+ */
+
+#ifndef __I915_DEBUGFS_PARAMS__
+#define __I915_DEBUGFS_PARAMS__
+
+struct dentry;
+struct drm_i915_private;
+
+struct dentry *i915_debugfs_params(struct drm_i915_private *i915);
+
+#endif /* __I915_DEBUGFS_PARAMS__ */

drivers/gpu/drm/i915/i915_params.c

@@ -35,7 +35,7 @@
 	MODULE_PARM_DESC(name, desc)
 
 struct i915_params i915_modparams __read_mostly = {
-#define MEMBER(T, member, value) .member = (value),
+#define MEMBER(T, member, value, ...) .member = (value),
 	I915_PARAMS_FOR_EACH(MEMBER)
 #undef MEMBER
 };

drivers/gpu/drm/i915/i915_params.h

@@ -36,49 +36,51 @@ struct drm_printer;
 /*
  * Invoke param, a function-like macro, for each i915 param, with arguments:
  *
- * param(type, name, value)
+ * param(type, name, value, mode)
  *
- * type: parameter type, one of {bool, int, unsigned int, char *}
+ * type: parameter type, one of {bool, int, unsigned int, unsigned long, char *}
  * name: name of the parameter
  * value: initial/default value of the parameter
+ * mode: debugfs file permissions, one of {0400, 0600, 0}, use 0 to not create
+ *       debugfs file
  */
 #define I915_PARAMS_FOR_EACH(param) \
-	param(char *, vbt_firmware, NULL) \
-	param(int, modeset, -1) \
-	param(int, lvds_channel_mode, 0) \
-	param(int, panel_use_ssc, -1) \
-	param(int, vbt_sdvo_panel_type, -1) \
-	param(int, enable_dc, -1) \
-	param(int, enable_fbc, -1) \
-	param(int, enable_psr, -1) \
-	param(int, disable_power_well, -1) \
-	param(int, enable_ips, 1) \
-	param(int, invert_brightness, 0) \
-	param(int, enable_guc, 0) \
-	param(int, guc_log_level, -1) \
-	param(char *, guc_firmware_path, NULL) \
-	param(char *, huc_firmware_path, NULL) \
-	param(char *, dmc_firmware_path, NULL) \
-	param(int, mmio_debug, -IS_ENABLED(CONFIG_DRM_I915_DEBUG_MMIO)) \
-	param(int, edp_vswing, 0) \
-	param(int, reset, 3) \
-	param(unsigned int, inject_probe_failure, 0) \
-	param(int, fastboot, -1) \
-	param(int, enable_dpcd_backlight, 0) \
-	param(char *, force_probe, CONFIG_DRM_I915_FORCE_PROBE) \
-	param(unsigned long, fake_lmem_start, 0) \
+	param(char *, vbt_firmware, NULL, 0400) \
+	param(int, modeset, -1, 0400) \
+	param(int, lvds_channel_mode, 0, 0400) \
+	param(int, panel_use_ssc, -1, 0600) \
+	param(int, vbt_sdvo_panel_type, -1, 0400) \
+	param(int, enable_dc, -1, 0400) \
+	param(int, enable_fbc, -1, 0600) \
+	param(int, enable_psr, -1, 0600) \
+	param(int, disable_power_well, -1, 0400) \
+	param(int, enable_ips, 1, 0600) \
+	param(int, invert_brightness, 0, 0600) \
+	param(int, enable_guc, 0, 0400) \
+	param(int, guc_log_level, -1, 0400) \
+	param(char *, guc_firmware_path, NULL, 0400) \
+	param(char *, huc_firmware_path, NULL, 0400) \
+	param(char *, dmc_firmware_path, NULL, 0400) \
+	param(int, mmio_debug, -IS_ENABLED(CONFIG_DRM_I915_DEBUG_MMIO), 0600) \
+	param(int, edp_vswing, 0, 0400) \
+	param(int, reset, 3, 0600) \
+	param(unsigned int, inject_probe_failure, 0, 0600) \
+	param(int, fastboot, -1, 0600) \
+	param(int, enable_dpcd_backlight, 0, 0600) \
+	param(char *, force_probe, CONFIG_DRM_I915_FORCE_PROBE, 0400) \
+	param(unsigned long, fake_lmem_start, 0, 0400) \
 	/* leave bools at the end to not create holes */ \
-	param(bool, alpha_support, IS_ENABLED(CONFIG_DRM_I915_ALPHA_SUPPORT)) \
-	param(bool, enable_hangcheck, true) \
-	param(bool, prefault_disable, false) \
-	param(bool, load_detect_test, false) \
-	param(bool, force_reset_modeset_test, false) \
-	param(bool, error_capture, true) \
-	param(bool, disable_display, false) \
-	param(bool, verbose_state_checks, true) \
-	param(bool, nuclear_pageflip, false) \
-	param(bool, enable_dp_mst, true) \
-	param(bool, enable_gvt, false)
+	param(bool, alpha_support, IS_ENABLED(CONFIG_DRM_I915_ALPHA_SUPPORT), 0400) \
+	param(bool, enable_hangcheck, true, 0600) \
+	param(bool, prefault_disable, false, 0600) \
+	param(bool, load_detect_test, false, 0600) \
+	param(bool, force_reset_modeset_test, false, 0600) \
+	param(bool, error_capture, true, 0600) \
+	param(bool, disable_display, false, 0400) \
+	param(bool, verbose_state_checks, true, 0) \
+	param(bool, nuclear_pageflip, false, 0400) \
+	param(bool, enable_dp_mst, true, 0600) \
+	param(bool, enable_gvt, false, 0400)
 
 #define MEMBER(T, member, ...) T member;
 struct i915_params {