drm/i915/display: Add framework to add parameters specific to display

Currently all module parameters are handled by i915_param.c/h. This
is a problem for display parameters when Xe driver is used. Add
a mechanism to add parameters specific to the display. This is mainly
copied from i915_[debugfs]_params.[ch]. Parameters are not yet moved. This
is done by subsequent patches.

v2:
  - Drop unused predefinition (dentry)
  - Clarify need for empty INTEL_DISPLAY_PARAMS_FOR_EACH in comment

Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231024124109.384973-2-jouni.hogander@intel.com

1 files changed, 176 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/display/intel_display_debugfs_params.c b/drivers/gpu/drm/i915/display/intel_display_debugfs_params.c
new file mode 100644
index 000000000000..b7e68eb62452
--- /dev/null
+++ b/drivers/gpu/drm/i915/display/intel_display_debugfs_params.c
@@ -0,0 +1,176 @@
+// SPDX-License-Identifier: MIT
+/*
+ * Copyright © 2023 Intel Corporation
+ */
+
+#include <linux/kernel.h>
+
+#include <drm/drm_drv.h>
+
+#include "intel_display_debugfs_params.h"
+#include "i915_drv.h"
+#include "intel_display_params.h"
+
+/* int param */
+static int intel_display_param_int_show(struct seq_file *m, void *data)
+{
+	int *value = m->private;
+
+	seq_printf(m, "%d\n", *value);
+
+	return 0;
+}
+
+static int intel_display_param_int_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, intel_display_param_int_show, inode->i_private);
+}
+
+static ssize_t intel_display_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);
+	if (ret) {
+		/* support boolean values too */
+		bool b;
+
+		ret = kstrtobool_from_user(ubuf, len, &b);
+		if (!ret)
+			*value = b;
+	}
+
+	return ret ?: len;
+}
+
+static const struct file_operations intel_display_param_int_fops = {
+	.owner = THIS_MODULE,
+	.open = intel_display_param_int_open,
+	.read = seq_read,
+	.write = intel_display_param_int_write,
+	.llseek = default_llseek,
+	.release = single_release,
+};
+
+static const struct file_operations intel_display_param_int_fops_ro = {
+	.owner = THIS_MODULE,
+	.open = intel_display_param_int_open,
+	.read = seq_read,
+	.llseek = default_llseek,
+	.release = single_release,
+};
+
+/* unsigned int param */
+static int intel_display_param_uint_show(struct seq_file *m, void *data)
+{
+	unsigned int *value = m->private;
+
+	seq_printf(m, "%u\n", *value);
+
+	return 0;
+}
+
+static int intel_display_param_uint_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, intel_display_param_uint_show, inode->i_private);
+}
+
+static ssize_t intel_display_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);
+	if (ret) {
+		/* support boolean values too */
+		bool b;
+
+		ret = kstrtobool_from_user(ubuf, len, &b);
+		if (!ret)
+			*value = b;
+	}
+
+	return ret ?: len;
+}
+
+static const struct file_operations intel_display_param_uint_fops = {
+	.owner = THIS_MODULE,
+	.open = intel_display_param_uint_open,
+	.read = seq_read,
+	.write = intel_display_param_uint_write,
+	.llseek = default_llseek,
+	.release = single_release,
+};
+
+static const struct file_operations intel_display_param_uint_fops_ro = {
+	.owner = THIS_MODULE,
+	.open = intel_display_param_uint_open,
+	.read = seq_read,
+	.llseek = default_llseek,
+	.release = single_release,
+};
+
+#define RO(mode) (((mode) & 0222) == 0)
+
+__maybe_unused static struct dentry *
+intel_display_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) ? &intel_display_param_int_fops_ro :
+					  &intel_display_param_int_fops);
+}
+
+__maybe_unused static struct dentry *
+intel_display_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) ? &intel_display_param_uint_fops_ro :
+					  &intel_display_param_uint_fops);
+}
+
+#define _intel_display_param_create_file(parent, name, mode, valp)	\
+	do {								\
+		if (mode)						\
+			_Generic(valp,					\
+				 bool * : debugfs_create_bool,		\
+				 int * : intel_display_debugfs_create_int, \
+				 unsigned int * : intel_display_debugfs_create_uint, \
+				 unsigned long * : debugfs_create_ulong, \
+				 char ** : debugfs_create_str) \
+				(name, mode, parent, valp);		\
+	} while (0)
+
+/* add a subdirectory with files for each intel display param */
+void intel_display_debugfs_params(struct drm_i915_private *i915)
+{
+	struct drm_minor *minor = i915->drm.primary;
+	struct dentry *dir;
+	char dirname[16];
+
+	snprintf(dirname, sizeof(dirname), "%s_params", i915->drm.driver->name);
+	dir = debugfs_lookup(dirname, minor->debugfs_root);
+	if (!dir)
+		dir = debugfs_create_dir(dirname, minor->debugfs_root);
+	if (IS_ERR(dir))
+		return;
+
+	/*
+	 * 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, ...) _intel_display_param_create_file( \
+		dir, #x, mode, &i915->display.params.x);
+	INTEL_DISPLAY_PARAMS_FOR_EACH(REGISTER);
+#undef REGISTER
+}