* [PATCH v2 1/1] platform/x86: Add coreboot CFR firmware attributes
2026-07-09 12:50 [PATCH v2 0/1] coreboot CFR firmware attributes Sean Rhodes
@ 2026-07-09 12:50 ` Sean Rhodes
2026-07-09 21:45 ` Julius Werner
2026-07-10 7:39 ` Uwe Kleine-König
0 siblings, 2 replies; 4+ messages in thread
From: Sean Rhodes @ 2026-07-09 12:50 UTC (permalink / raw)
To: platform-driver-x86
Cc: Tzung-Bi Shih, Brian Norris, Julius Werner, Hans de Goede,
Ilpo Järvinen, Sean Rhodes, linux-kernel, chrome-platform
coreboot can publish a CFR tree in its coreboot table to describe
firmware setup options. Add a firmware-attributes driver for that table
entry and move the coreboot table bus definitions into <linux/coreboot.h>
so the driver can bind from outside drivers/firmware/google.
The driver exposes runtime EFI variable-backed boolean, enum and integer
settings through the firmware-attributes ABI. It only registers settings
with readable runtime EFI variables, skips suppressed, volatile,
dependency-gated and non-runtime options, and keeps read-only or inactive
options read-only in sysfs.
For settings with an APM_CNT runtime-apply record, write the EFI variable
and ask firmware to apply the setting immediately. If firmware reports a
failure, restore the old EFI variable value. Settings without a runtime
apply hook keep the EFI variable update and set pending_reboot.
Tested on a Star Labs Byte with firmware 26.07 and the driver built as a
module against Linux 6.17: runtime APM_CNT apply was verified with
power_led, and reboot-needed behavior was verified with debug_level.
Link: https://doc.coreboot.org/drivers/cfr.html
Link: https://doc.coreboot.org/drivers/cfr_internal.html
Signed-off-by: Sean Rhodes <sean@starlabs.systems>
---
MAINTAINERS | 6 +
drivers/firmware/google/coreboot_table.h | 45 --
drivers/platform/x86/Kconfig | 13 +
drivers/platform/x86/Makefile | 1 +
drivers/platform/x86/coreboot-cfr.c | 986 +++++++++++++++++++++++
include/linux/coreboot.h | 147 ++++
6 files changed, 1153 insertions(+), 45 deletions(-)
create mode 100644 drivers/platform/x86/coreboot-cfr.c
diff --git a/MAINTAINERS b/MAINTAINERS
index 15011f5752a9..c5d8daab2196 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -6665,6 +6665,12 @@ F: tools/testing/selftests/cgroup/test_hugetlb_memcg.c
F: tools/testing/selftests/cgroup/test_kmem.c
F: tools/testing/selftests/cgroup/test_memcontrol.c
+COREBOOT CFR FIRMWARE ATTRIBUTES DRIVER
+M: Sean Rhodes <sean@starlabs.systems>
+L: platform-driver-x86@vger.kernel.org
+S: Maintained
+F: drivers/platform/x86/coreboot-cfr.c
+
CORETEMP HARDWARE MONITORING DRIVER
L: linux-hwmon@vger.kernel.org
S: Orphan
diff --git a/drivers/firmware/google/coreboot_table.h b/drivers/firmware/google/coreboot_table.h
index 616ca3903e5c..0c4956d3836a 100644
--- a/drivers/firmware/google/coreboot_table.h
+++ b/drivers/firmware/google/coreboot_table.h
@@ -13,50 +13,5 @@
#define __COREBOOT_TABLE_H
#include <linux/coreboot.h>
-#include <linux/device.h>
-
-/* A device, additionally with information from coreboot. */
-struct coreboot_device {
- struct device dev;
- union {
- struct coreboot_table_entry entry;
- struct lb_cbmem_ref cbmem_ref;
- struct lb_cbmem_entry cbmem_entry;
- struct lb_framebuffer framebuffer;
- DECLARE_FLEX_ARRAY(u8, raw);
- };
-};
-
-static inline struct coreboot_device *dev_to_coreboot_device(struct device *dev)
-{
- return container_of(dev, struct coreboot_device, dev);
-}
-
-/* A driver for handling devices described in coreboot tables. */
-struct coreboot_driver {
- int (*probe)(struct coreboot_device *);
- void (*remove)(struct coreboot_device *);
- struct device_driver drv;
- const struct coreboot_device_id *id_table;
-};
-
-/* use a macro to avoid include chaining to get THIS_MODULE */
-#define coreboot_driver_register(driver) \
- __coreboot_driver_register(driver, THIS_MODULE)
-/* Register a driver that uses the data from a coreboot table. */
-int __coreboot_driver_register(struct coreboot_driver *driver,
- struct module *owner);
-
-/* Unregister a driver that uses the data from a coreboot table. */
-void coreboot_driver_unregister(struct coreboot_driver *driver);
-
-/* module_coreboot_driver() - Helper macro for drivers that don't do
- * anything special in module init/exit. This eliminates a lot of
- * boilerplate. Each module may only use this macro once, and
- * calling it replaces module_init() and module_exit()
- */
-#define module_coreboot_driver(__coreboot_driver) \
- module_driver(__coreboot_driver, coreboot_driver_register, \
- coreboot_driver_unregister)
#endif /* __COREBOOT_TABLE_H */
diff --git a/drivers/platform/x86/Kconfig b/drivers/platform/x86/Kconfig
index b54b5212b204..683c35a9d288 100644
--- a/drivers/platform/x86/Kconfig
+++ b/drivers/platform/x86/Kconfig
@@ -851,6 +851,19 @@ config SONYPI_COMPAT
help
Build the sonypi driver compatibility code into the sony-laptop driver.
+config COREBOOT_CFR
+ tristate "coreboot CFR firmware attributes"
+ depends on EFI
+ depends on GOOGLE_COREBOOT_TABLE
+ select FW_ATTR_CLASS
+ help
+ This driver parses the coreboot CFR table and exposes runtime EFI
+ variable-backed options through the firmware-attributes sysfs
+ interface.
+
+ If you have a system running coreboot with CFR runtime
+ configuration support, say Y or M here.
+
config SYSTEM76_ACPI
tristate "System76 ACPI Driver"
depends on ACPI_EC
diff --git a/drivers/platform/x86/Makefile b/drivers/platform/x86/Makefile
index 872ac3842391..71a0378e4d9b 100644
--- a/drivers/platform/x86/Makefile
+++ b/drivers/platform/x86/Makefile
@@ -129,6 +129,7 @@ obj-$(CONFIG_COMPAL_LAPTOP) += compal-laptop.o
obj-$(CONFIG_LG_LAPTOP) += lg-laptop.o
obj-$(CONFIG_PANASONIC_LAPTOP) += panasonic-laptop.o
obj-$(CONFIG_SONY_LAPTOP) += sony-laptop.o
+obj-$(CONFIG_COREBOOT_CFR) += coreboot-cfr.o
obj-$(CONFIG_SYSTEM76_ACPI) += system76_acpi.o
obj-$(CONFIG_TOPSTAR_LAPTOP) += topstar-laptop.o
diff --git a/drivers/platform/x86/coreboot-cfr.c b/drivers/platform/x86/coreboot-cfr.c
new file mode 100644
index 000000000000..9fc4fd1f2140
--- /dev/null
+++ b/drivers/platform/x86/coreboot-cfr.c
@@ -0,0 +1,986 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * coreboot CFR firmware attributes driver.
+ *
+ * Parses LB_TAG_CFR_ROOT records from the coreboot table and exposes
+ * runtime EFI variable-backed options through the firmware-attributes class.
+ */
+
+#include <linux/array_size.h>
+#include <linux/bitops.h>
+#include <linux/cleanup.h>
+#include <linux/coreboot.h>
+#include <linux/ctype.h>
+#include <linux/efi.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/kdev_t.h>
+#include <linux/kobject.h>
+#include <linux/limits.h>
+#include <linux/list.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <linux/sysfs.h>
+#include <linux/types.h>
+
+#include "firmware_attributes_class.h"
+
+#define DRIVER_NAME "coreboot-cfr"
+
+#define COREBOOT_CFR_OPT_SKIP_FLAGS \
+ (CFR_OPTFLAG_SUPPRESS | CFR_OPTFLAG_VOLATILE)
+
+#define COREBOOT_CFR_OPT_READ_ONLY_FLAGS \
+ (CFR_OPTFLAG_READONLY | CFR_OPTFLAG_INACTIVE)
+
+#define COREBOOT_CFR_EFI_ATTRS \
+ (EFI_VARIABLE_NON_VOLATILE | EFI_VARIABLE_BOOTSERVICE_ACCESS | \
+ EFI_VARIABLE_RUNTIME_ACCESS)
+
+#define COREBOOT_CFR_APM_CNT_PORT 0xb2
+#define COREBOOT_CFR_APM_STS_PORT 0xb3
+#define COREBOOT_CFR_APM_APPLY_CMD 0xe3
+
+static efi_guid_t coreboot_cfr_guid = EFI_GUID(0xceae4c1d, 0x335b, 0x4685,
+ 0xa4, 0xa0, 0xfc, 0x4a,
+ 0x94, 0xee, 0xa0, 0x85);
+
+enum coreboot_cfr_setting_type {
+ COREBOOT_CFR_SETTING_ENUM,
+ COREBOOT_CFR_SETTING_NUMBER,
+ COREBOOT_CFR_SETTING_BOOL,
+};
+
+struct coreboot_cfr_enum {
+ char *label;
+ u32 value;
+};
+
+struct coreboot_cfr_setting {
+ struct kobject kobj;
+ struct list_head node;
+ struct coreboot_cfr_drvdata *drvdata;
+ enum coreboot_cfr_setting_type type;
+ char *name;
+ char *display_name;
+ struct coreboot_cfr_enum *values;
+ unsigned int n_values;
+ u32 default_value;
+ u32 min;
+ u32 max;
+ u32 step;
+ u32 runtime_apply_method;
+ u32 runtime_apply_id;
+ bool read_only;
+};
+
+struct coreboot_cfr_drvdata {
+ struct device *class_dev;
+ struct kset *attrs_kset;
+ struct list_head settings;
+ /* Serializes EFI variable writes and the matching runtime apply hook. */
+ struct mutex lock;
+ bool pending_reboot;
+};
+
+static struct coreboot_cfr_drvdata *coreboot_cfr_data;
+
+static struct coreboot_cfr_setting *to_coreboot_cfr_setting(struct kobject *kobj)
+{
+ return container_of(kobj, struct coreboot_cfr_setting, kobj);
+}
+
+static bool coreboot_cfr_string_is_valid_name(const char *name)
+{
+ return name && name[0] && !strchr(name, '/');
+}
+
+static char *coreboot_cfr_string_dup(const struct lb_cfr_varbinary *str)
+{
+ const char *data = (const char *)str + sizeof(*str);
+ size_t len = str->data_length;
+
+ if (len && !data[len - 1])
+ len--;
+
+ return kmemdup_nul(data, len, GFP_KERNEL);
+}
+
+static const struct coreboot_table_entry *
+coreboot_cfr_child_entry(const void *base, size_t len, u32 tag)
+{
+ const struct coreboot_table_entry *entry;
+ size_t off = 0;
+
+ while (off < len) {
+ if (len - off < sizeof(*entry))
+ return NULL;
+
+ entry = base + off;
+ if (entry->size < sizeof(*entry) || entry->size > len - off)
+ return NULL;
+
+ if (entry->tag == tag)
+ return entry;
+
+ off += entry->size;
+ }
+
+ return NULL;
+}
+
+static const struct lb_cfr_varbinary *
+coreboot_cfr_child_string(const void *base, size_t len, u32 tag)
+{
+ const struct lb_cfr_varbinary *str;
+ const struct coreboot_table_entry *entry;
+
+ entry = coreboot_cfr_child_entry(base, len, tag);
+ if (!entry)
+ return NULL;
+
+ if (entry->size < sizeof(*str))
+ return NULL;
+
+ str = (const struct lb_cfr_varbinary *)entry;
+ if (str->data_length > entry->size - sizeof(*str))
+ return NULL;
+
+ return str;
+}
+
+static const struct lb_cfr_runtime_apply *
+coreboot_cfr_child_runtime_apply(const void *base, size_t len)
+{
+ const struct lb_cfr_runtime_apply *runtime_apply;
+ const struct coreboot_table_entry *entry;
+
+ entry = coreboot_cfr_child_entry(base, len, CFR_TAG_RUNTIME_APPLY);
+ if (!entry)
+ return NULL;
+
+ if (entry->size < sizeof(*runtime_apply))
+ return ERR_PTR(-EINVAL);
+
+ runtime_apply = (const struct lb_cfr_runtime_apply *)entry;
+ if (runtime_apply->method == CFR_RUNTIME_APPLY_APM_CNT &&
+ runtime_apply->id > U8_MAX)
+ return ERR_PTR(-EINVAL);
+
+ return runtime_apply;
+}
+
+static efi_char16_t *coreboot_cfr_efi_name(const char *name)
+{
+ size_t len, i;
+
+ len = strlen(name);
+ if (len >= EFI_VAR_NAME_LEN)
+ return ERR_PTR(-ENAMETOOLONG);
+
+ efi_char16_t *efi_name __free(kfree) =
+ kcalloc(len + 1, sizeof(*efi_name), GFP_KERNEL);
+ if (!efi_name)
+ return ERR_PTR(-ENOMEM);
+
+ for (i = 0; i < len; i++) {
+ if (!isascii(name[i]))
+ return ERR_PTR(-EINVAL);
+ efi_name[i] = name[i];
+ }
+
+ return no_free_ptr(efi_name);
+}
+
+static int coreboot_cfr_read_value(const struct coreboot_cfr_setting *setting,
+ u32 *value, u32 *attrs)
+{
+ unsigned long size = sizeof(__le32);
+ efi_char16_t *efi_name;
+ efi_status_t status;
+ __le32 data;
+ u32 attr;
+
+ efi_name = coreboot_cfr_efi_name(setting->name);
+ if (IS_ERR(efi_name))
+ return PTR_ERR(efi_name);
+
+ status = efivar_get_variable(efi_name, &coreboot_cfr_guid, &attr,
+ &size, &data);
+ kfree(efi_name);
+ if (status != EFI_SUCCESS)
+ return efi_status_to_err(status);
+
+ if (size != sizeof(data))
+ return -EINVAL;
+
+ if (!(attr & EFI_VARIABLE_RUNTIME_ACCESS))
+ return -EOPNOTSUPP;
+
+ *value = le32_to_cpu(data);
+ if (attrs)
+ *attrs = attr;
+
+ return 0;
+}
+
+static int coreboot_cfr_write_efi_value(struct coreboot_cfr_setting *setting,
+ u32 value, u32 attrs)
+{
+ efi_char16_t *efi_name;
+ efi_status_t status;
+ __le32 data;
+
+ efi_name = coreboot_cfr_efi_name(setting->name);
+ if (IS_ERR(efi_name))
+ return PTR_ERR(efi_name);
+
+ data = cpu_to_le32(value);
+ status = efivar_set_variable(efi_name, &coreboot_cfr_guid, attrs,
+ sizeof(data), &data);
+ kfree(efi_name);
+ if (status != EFI_SUCCESS)
+ return efi_status_to_err(status);
+
+ return 0;
+}
+
+static int coreboot_cfr_apply_runtime(struct coreboot_cfr_setting *setting)
+{
+ u8 status;
+
+ if (setting->runtime_apply_method != CFR_RUNTIME_APPLY_APM_CNT ||
+ !setting->runtime_apply_id)
+ return -EOPNOTSUPP;
+
+ outb((u8)setting->runtime_apply_id, COREBOOT_CFR_APM_STS_PORT);
+ outb(COREBOOT_CFR_APM_APPLY_CMD, COREBOOT_CFR_APM_CNT_PORT);
+ status = inb(COREBOOT_CFR_APM_STS_PORT);
+ if (status)
+ return -EIO;
+
+ return 0;
+}
+
+static int coreboot_cfr_write_value(struct coreboot_cfr_setting *setting,
+ u32 value)
+{
+ u32 attrs;
+ u32 old;
+ int ret;
+ bool changed = false;
+
+ if (setting->read_only)
+ return -EACCES;
+
+ scoped_guard(mutex, &setting->drvdata->lock) {
+ ret = coreboot_cfr_read_value(setting, &old, &attrs);
+ if (ret)
+ return ret;
+
+ if ((attrs & COREBOOT_CFR_EFI_ATTRS) != COREBOOT_CFR_EFI_ATTRS)
+ return -EOPNOTSUPP;
+
+ ret = coreboot_cfr_write_efi_value(setting, value, attrs);
+ if (ret)
+ return ret;
+ changed = true;
+
+ ret = coreboot_cfr_apply_runtime(setting);
+ if (ret == -EOPNOTSUPP) {
+ /* EFI changed; firmware will consume it after reboot. */
+ setting->drvdata->pending_reboot = true;
+ ret = 0;
+ } else if (ret) {
+ int restore_ret;
+
+ restore_ret = coreboot_cfr_write_efi_value(setting, old, attrs);
+ if (restore_ret)
+ ret = restore_ret;
+ else
+ changed = false;
+ }
+ }
+
+ if (changed)
+ kobject_uevent(&setting->drvdata->class_dev->kobj, KOBJ_CHANGE);
+ return ret;
+}
+
+static const char *
+coreboot_cfr_label_from_value(const struct coreboot_cfr_setting *setting,
+ u32 value)
+{
+ unsigned int i;
+
+ for (i = 0; i < setting->n_values; i++) {
+ if (setting->values[i].value == value)
+ return setting->values[i].label;
+ }
+
+ return NULL;
+}
+
+static int coreboot_cfr_parse_value(struct coreboot_cfr_setting *setting,
+ const char *label, u32 *value_out)
+{
+ unsigned int i;
+
+ for (i = 0; i < setting->n_values; i++) {
+ if (!sysfs_streq(label, setting->values[i].label))
+ continue;
+
+ *value_out = setting->values[i].value;
+ return 0;
+ }
+
+ return kstrtou32(label, 0, value_out);
+}
+
+static bool coreboot_cfr_value_is_valid(struct coreboot_cfr_setting *setting,
+ u32 value)
+{
+ u32 delta;
+
+ if (setting->type != COREBOOT_CFR_SETTING_NUMBER)
+ return coreboot_cfr_label_from_value(setting, value);
+
+ if (value < setting->min || value > setting->max)
+ return false;
+
+ if (!setting->step)
+ return true;
+
+ delta = value - setting->min;
+ return delta % setting->step == 0;
+}
+
+static ssize_t type_show(struct kobject *kobj, struct kobj_attribute *attr,
+ char *buf)
+{
+ struct coreboot_cfr_setting *setting = to_coreboot_cfr_setting(kobj);
+
+ if (setting->type == COREBOOT_CFR_SETTING_NUMBER)
+ return sysfs_emit(buf, "integer\n");
+
+ return sysfs_emit(buf, "enumeration\n");
+}
+
+static ssize_t display_name_language_code_show(struct kobject *kobj,
+ struct kobj_attribute *attr,
+ char *buf)
+{
+ return sysfs_emit(buf, "en_US.UTF-8\n");
+}
+
+static ssize_t display_name_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ struct coreboot_cfr_setting *setting = to_coreboot_cfr_setting(kobj);
+
+ return sysfs_emit(buf, "%s\n", setting->display_name);
+}
+
+static ssize_t possible_values_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ struct coreboot_cfr_setting *setting = to_coreboot_cfr_setting(kobj);
+ ssize_t len = 0;
+ unsigned int i;
+
+ for (i = 0; i < setting->n_values; i++) {
+ len += sysfs_emit_at(buf, len, "%s%s", i ? ";" : "",
+ setting->values[i].label);
+ if (len >= PAGE_SIZE)
+ return len;
+ }
+
+ len += sysfs_emit_at(buf, len, "\n");
+ return len;
+}
+
+static ssize_t min_value_show(struct kobject *kobj, struct kobj_attribute *attr,
+ char *buf)
+{
+ struct coreboot_cfr_setting *setting = to_coreboot_cfr_setting(kobj);
+
+ return sysfs_emit(buf, "%u\n", setting->min);
+}
+
+static ssize_t max_value_show(struct kobject *kobj, struct kobj_attribute *attr,
+ char *buf)
+{
+ struct coreboot_cfr_setting *setting = to_coreboot_cfr_setting(kobj);
+
+ return sysfs_emit(buf, "%u\n", setting->max);
+}
+
+static ssize_t scalar_increment_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ struct coreboot_cfr_setting *setting = to_coreboot_cfr_setting(kobj);
+
+ return sysfs_emit(buf, "%u\n", setting->step);
+}
+
+static ssize_t default_value_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ struct coreboot_cfr_setting *setting = to_coreboot_cfr_setting(kobj);
+ const char *label;
+
+ if (setting->type == COREBOOT_CFR_SETTING_NUMBER)
+ return sysfs_emit(buf, "%u\n", setting->default_value);
+
+ label = coreboot_cfr_label_from_value(setting, setting->default_value);
+ if (!label)
+ return sysfs_emit(buf, "%u\n", setting->default_value);
+
+ return sysfs_emit(buf, "%s\n", label);
+}
+
+static ssize_t current_value_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ struct coreboot_cfr_setting *setting = to_coreboot_cfr_setting(kobj);
+ const char *label;
+ u32 value;
+ int ret;
+
+ ret = coreboot_cfr_read_value(setting, &value, NULL);
+ if (ret)
+ return ret;
+
+ if (setting->type == COREBOOT_CFR_SETTING_NUMBER)
+ return sysfs_emit(buf, "%u\n", value);
+
+ label = coreboot_cfr_label_from_value(setting, value);
+ if (!label)
+ return -EINVAL;
+
+ return sysfs_emit(buf, "%s\n", label);
+}
+
+static ssize_t current_value_store(struct kobject *kobj,
+ struct kobj_attribute *attr,
+ const char *buf, size_t count)
+{
+ struct coreboot_cfr_setting *setting = to_coreboot_cfr_setting(kobj);
+ u32 value;
+ int ret;
+
+ ret = coreboot_cfr_parse_value(setting, buf, &value);
+ if (ret)
+ return ret;
+
+ if (!coreboot_cfr_value_is_valid(setting, value))
+ return -EINVAL;
+
+ ret = coreboot_cfr_write_value(setting, value);
+ if (ret)
+ return ret;
+
+ return count;
+}
+
+static struct kobj_attribute type_attr = __ATTR_RO(type);
+static struct kobj_attribute display_name_language_code_attr =
+ __ATTR_RO(display_name_language_code);
+static struct kobj_attribute display_name_attr = __ATTR_RO(display_name);
+static struct kobj_attribute possible_values_attr = __ATTR_RO(possible_values);
+static struct kobj_attribute min_value_attr = __ATTR_RO(min_value);
+static struct kobj_attribute max_value_attr = __ATTR_RO(max_value);
+static struct kobj_attribute scalar_increment_attr = __ATTR_RO(scalar_increment);
+static struct kobj_attribute default_value_attr = __ATTR_RO(default_value);
+static struct kobj_attribute current_value_attr = __ATTR_RW(current_value);
+
+static struct attribute *coreboot_cfr_setting_attrs[] = {
+ &type_attr.attr,
+ &display_name_language_code_attr.attr,
+ &display_name_attr.attr,
+ &possible_values_attr.attr,
+ &min_value_attr.attr,
+ &max_value_attr.attr,
+ &scalar_increment_attr.attr,
+ &default_value_attr.attr,
+ ¤t_value_attr.attr,
+ NULL,
+};
+
+static umode_t coreboot_cfr_attr_is_visible(struct kobject *kobj,
+ struct attribute *attr, int n)
+{
+ struct coreboot_cfr_setting *setting = to_coreboot_cfr_setting(kobj);
+
+ if (setting->type == COREBOOT_CFR_SETTING_NUMBER &&
+ attr == &possible_values_attr.attr)
+ return 0;
+
+ if (setting->type != COREBOOT_CFR_SETTING_NUMBER &&
+ (attr == &min_value_attr.attr || attr == &max_value_attr.attr ||
+ attr == &scalar_increment_attr.attr))
+ return 0;
+
+ if (setting->read_only && attr == ¤t_value_attr.attr)
+ return 0444;
+
+ return attr->mode;
+}
+
+static const struct attribute_group coreboot_cfr_setting_group = {
+ .attrs = coreboot_cfr_setting_attrs,
+ .is_visible = coreboot_cfr_attr_is_visible,
+};
+
+static void coreboot_cfr_free_setting(struct coreboot_cfr_setting *setting)
+{
+ unsigned int i;
+
+ for (i = 0; i < setting->n_values; i++)
+ kfree(setting->values[i].label);
+
+ kfree(setting->values);
+ kfree(setting->display_name);
+ kfree(setting->name);
+ kfree(setting);
+}
+
+static void coreboot_cfr_setting_release(struct kobject *kobj)
+{
+ coreboot_cfr_free_setting(to_coreboot_cfr_setting(kobj));
+}
+
+static const struct kobj_type coreboot_cfr_setting_ktype = {
+ .release = coreboot_cfr_setting_release,
+ .sysfs_ops = &kobj_sysfs_ops,
+};
+
+static ssize_t pending_reboot_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ return sysfs_emit(buf, "%d\n",
+ coreboot_cfr_data && coreboot_cfr_data->pending_reboot);
+}
+
+static struct kobj_attribute pending_reboot_attr = __ATTR_RO(pending_reboot);
+
+static int coreboot_cfr_copy_bool_values(struct coreboot_cfr_setting *setting)
+{
+ static const struct coreboot_cfr_enum bool_values[] = {
+ { .label = "Disabled", .value = 0 },
+ { .label = "Enabled", .value = 1 },
+ };
+ unsigned int i;
+
+ setting->values = kcalloc(ARRAY_SIZE(bool_values), sizeof(*setting->values),
+ GFP_KERNEL);
+ if (!setting->values)
+ return -ENOMEM;
+
+ for (i = 0; i < ARRAY_SIZE(bool_values); i++) {
+ setting->values[i].label = kstrdup(bool_values[i].label,
+ GFP_KERNEL);
+ if (!setting->values[i].label)
+ return -ENOMEM;
+ setting->values[i].value = bool_values[i].value;
+ setting->n_values++;
+ }
+
+ return 0;
+}
+
+static int coreboot_cfr_count_enum_values(const void *base, size_t len)
+{
+ const struct coreboot_table_entry *entry;
+ size_t off = 0;
+ int count = 0;
+
+ while (off < len) {
+ if (len - off < sizeof(*entry))
+ return -EINVAL;
+
+ entry = base + off;
+ if (entry->size < sizeof(*entry) || entry->size > len - off)
+ return -EINVAL;
+
+ if (entry->tag == CFR_TAG_ENUM_VALUE)
+ count++;
+
+ off += entry->size;
+ }
+
+ return count;
+}
+
+static int coreboot_cfr_copy_enum_values(struct coreboot_cfr_setting *setting,
+ const void *base, size_t len)
+{
+ const struct lb_cfr_enum_value *enum_value;
+ const struct lb_cfr_varbinary *label;
+ const struct coreboot_table_entry *entry;
+ size_t off = 0;
+ int count;
+
+ count = coreboot_cfr_count_enum_values(base, len);
+ if (count <= 0)
+ return count ?: -EINVAL;
+
+ setting->values = kcalloc(count, sizeof(*setting->values), GFP_KERNEL);
+ if (!setting->values)
+ return -ENOMEM;
+
+ while (off < len) {
+ entry = base + off;
+ if (entry->tag != CFR_TAG_ENUM_VALUE) {
+ off += entry->size;
+ continue;
+ }
+
+ if (entry->size < sizeof(*enum_value))
+ return -EINVAL;
+
+ enum_value = base + off;
+ label = coreboot_cfr_child_string(enum_value + 1,
+ enum_value->size - sizeof(*enum_value),
+ CFR_TAG_VARCHAR_UI_NAME);
+ if (!label)
+ return -EINVAL;
+
+ setting->values[setting->n_values].label =
+ coreboot_cfr_string_dup(label);
+ if (!setting->values[setting->n_values].label)
+ return -ENOMEM;
+
+ setting->values[setting->n_values].value = enum_value->value;
+ setting->n_values++;
+ off += entry->size;
+ }
+
+ return 0;
+}
+
+static int coreboot_cfr_setting_is_usable(struct coreboot_cfr_setting *setting)
+{
+ u32 value;
+ int ret;
+
+ ret = coreboot_cfr_read_value(setting, &value, NULL);
+ if (ret)
+ return ret;
+
+ if (!coreboot_cfr_value_is_valid(setting, value))
+ return -EINVAL;
+
+ return 0;
+}
+
+static int coreboot_cfr_register_setting(struct coreboot_cfr_drvdata *data,
+ struct coreboot_cfr_setting *setting)
+{
+ int ret;
+
+ ret = kobject_init_and_add(&setting->kobj, &coreboot_cfr_setting_ktype,
+ &data->attrs_kset->kobj, "%s", setting->name);
+ if (ret) {
+ kobject_put(&setting->kobj);
+ return ret;
+ }
+
+ ret = sysfs_create_group(&setting->kobj, &coreboot_cfr_setting_group);
+ if (ret) {
+ kobject_put(&setting->kobj);
+ return ret;
+ }
+
+ list_add_tail(&setting->node, &data->settings);
+ return 0;
+}
+
+static int coreboot_cfr_add_numeric_option(struct coreboot_cfr_drvdata *data,
+ const struct lb_cfr_numeric_option *option)
+{
+ const struct lb_cfr_varbinary *name;
+ const struct lb_cfr_varbinary *display_name;
+ const struct lb_cfr_runtime_apply *runtime_apply;
+ const void *child_base = option + 1;
+ struct coreboot_cfr_setting *setting;
+ size_t child_len = option->size - sizeof(*option);
+ int ret;
+
+ if (!(option->flags & CFR_OPTFLAG_RUNTIME))
+ return 0;
+
+ if (option->flags & COREBOOT_CFR_OPT_SKIP_FLAGS)
+ return 0;
+
+ if (option->dependency_id)
+ return 0;
+
+ setting = kzalloc_obj(*setting, GFP_KERNEL);
+ if (!setting)
+ return -ENOMEM;
+
+ INIT_LIST_HEAD(&setting->node);
+ setting->drvdata = data;
+ setting->default_value = option->default_value;
+ setting->min = option->min;
+ setting->max = option->max;
+ setting->step = option->step ?: 1;
+ setting->read_only = option->flags & COREBOOT_CFR_OPT_READ_ONLY_FLAGS;
+
+ runtime_apply = coreboot_cfr_child_runtime_apply(child_base, child_len);
+ if (IS_ERR(runtime_apply)) {
+ ret = PTR_ERR(runtime_apply);
+ goto err_put_setting;
+ }
+
+ if (runtime_apply && runtime_apply->method == CFR_RUNTIME_APPLY_APM_CNT &&
+ runtime_apply->id) {
+ setting->runtime_apply_method = runtime_apply->method;
+ setting->runtime_apply_id = runtime_apply->id;
+ }
+
+ name = coreboot_cfr_child_string(child_base, child_len,
+ CFR_TAG_VARCHAR_OPT_NAME);
+ if (!name) {
+ ret = -EINVAL;
+ goto err_put_setting;
+ }
+
+ setting->name = coreboot_cfr_string_dup(name);
+ if (!setting->name) {
+ ret = -ENOMEM;
+ goto err_put_setting;
+ }
+
+ if (!coreboot_cfr_string_is_valid_name(setting->name)) {
+ ret = -EINVAL;
+ goto err_put_setting;
+ }
+
+ display_name = coreboot_cfr_child_string(child_base, child_len,
+ CFR_TAG_VARCHAR_UI_NAME);
+ if (display_name)
+ setting->display_name = coreboot_cfr_string_dup(display_name);
+ else
+ setting->display_name = kstrdup(setting->name, GFP_KERNEL);
+ if (!setting->display_name) {
+ ret = -ENOMEM;
+ goto err_put_setting;
+ }
+
+ switch (option->tag) {
+ case CFR_TAG_OPTION_BOOL:
+ setting->type = COREBOOT_CFR_SETTING_BOOL;
+ setting->min = 0;
+ setting->max = 1;
+ setting->step = 1;
+ ret = coreboot_cfr_copy_bool_values(setting);
+ break;
+ case CFR_TAG_OPTION_ENUM:
+ setting->type = COREBOOT_CFR_SETTING_ENUM;
+ ret = coreboot_cfr_copy_enum_values(setting, child_base,
+ child_len);
+ break;
+ case CFR_TAG_OPTION_NUMBER:
+ setting->type = COREBOOT_CFR_SETTING_NUMBER;
+ if (!setting->min && !setting->max)
+ setting->max = U32_MAX;
+ else if (setting->max < setting->min)
+ setting->max = U32_MAX;
+ ret = 0;
+ break;
+ default:
+ ret = -EINVAL;
+ break;
+ }
+
+ if (ret)
+ goto err_put_setting;
+
+ ret = coreboot_cfr_setting_is_usable(setting);
+ if (ret) {
+ ret = 0;
+ goto err_put_setting;
+ }
+
+ ret = coreboot_cfr_register_setting(data, setting);
+ if (ret)
+ return ret;
+
+ return 0;
+
+err_put_setting:
+ coreboot_cfr_free_setting(setting);
+ return ret;
+}
+
+static int coreboot_cfr_parse_records(struct coreboot_cfr_drvdata *data,
+ const void *base, size_t len)
+{
+ const struct coreboot_table_entry *entry;
+ const void *child_base;
+ size_t child_len;
+ size_t off = 0;
+ int ret;
+
+ while (off < len) {
+ if (len - off < sizeof(*entry))
+ return -EINVAL;
+
+ entry = base + off;
+ if (entry->size < sizeof(*entry) || entry->size > len - off)
+ return -EINVAL;
+
+ switch (entry->tag) {
+ case CFR_TAG_OPTION_FORM:
+ if (entry->size < sizeof(struct lb_cfr_option_form))
+ return -EINVAL;
+
+ child_base = base + off + sizeof(struct lb_cfr_option_form);
+ child_len = entry->size - sizeof(struct lb_cfr_option_form);
+ ret = coreboot_cfr_parse_records(data, child_base,
+ child_len);
+ if (ret)
+ return ret;
+ break;
+ case CFR_TAG_OPTION_ENUM:
+ case CFR_TAG_OPTION_NUMBER:
+ case CFR_TAG_OPTION_BOOL:
+ if (entry->size < sizeof(struct lb_cfr_numeric_option))
+ return -EINVAL;
+ ret = coreboot_cfr_add_numeric_option(data, base + off);
+ if (ret)
+ return ret;
+ break;
+ default:
+ break;
+ }
+
+ off += entry->size;
+ }
+
+ return 0;
+}
+
+static void coreboot_cfr_unregister_settings(struct coreboot_cfr_drvdata *data)
+{
+ struct coreboot_cfr_setting *setting, *tmp;
+
+ list_for_each_entry_safe(setting, tmp, &data->settings, node) {
+ sysfs_remove_group(&setting->kobj, &coreboot_cfr_setting_group);
+ list_del(&setting->node);
+ kobject_put(&setting->kobj);
+ }
+}
+
+static int coreboot_cfr_probe(struct coreboot_device *dev)
+{
+ const struct lb_cfr *root = (const struct lb_cfr *)dev->raw;
+ struct coreboot_cfr_drvdata *data;
+ size_t payload_len;
+ int ret;
+
+ if (dev->entry.size < sizeof(*root))
+ return -EINVAL;
+
+ if (root->tag != LB_TAG_CFR_ROOT || root->version != CFR_VERSION)
+ return -EINVAL;
+
+ if (root->size < sizeof(*root) || root->size > dev->entry.size)
+ return -EINVAL;
+
+ if (!efivar_is_available())
+ return -EPROBE_DEFER;
+
+ data = devm_kzalloc(&dev->dev, sizeof(*data), GFP_KERNEL);
+ if (!data)
+ return -ENOMEM;
+
+ INIT_LIST_HEAD(&data->settings);
+ ret = devm_mutex_init(&dev->dev, &data->lock);
+ if (ret)
+ return ret;
+
+ dev_set_drvdata(&dev->dev, data);
+ coreboot_cfr_data = data;
+
+ data->class_dev = device_create(&firmware_attributes_class, NULL,
+ MKDEV(0, 0), NULL, DRIVER_NAME);
+ if (IS_ERR(data->class_dev)) {
+ ret = PTR_ERR(data->class_dev);
+ goto err_clear_data;
+ }
+
+ data->attrs_kset = kset_create_and_add("attributes", NULL,
+ &data->class_dev->kobj);
+ if (!data->attrs_kset) {
+ ret = -ENOMEM;
+ goto err_unregister_dev;
+ }
+
+ ret = sysfs_create_file(&data->attrs_kset->kobj,
+ &pending_reboot_attr.attr);
+ if (ret)
+ goto err_unregister_attrs;
+
+ payload_len = root->size - sizeof(*root);
+ ret = coreboot_cfr_parse_records(data, root + 1, payload_len);
+ if (ret)
+ goto err_unregister_settings;
+
+ if (list_empty(&data->settings)) {
+ ret = -ENODEV;
+ goto err_unregister_settings;
+ }
+
+ return 0;
+
+err_unregister_settings:
+ coreboot_cfr_unregister_settings(data);
+ sysfs_remove_file(&data->attrs_kset->kobj, &pending_reboot_attr.attr);
+err_unregister_attrs:
+ kset_unregister(data->attrs_kset);
+err_unregister_dev:
+ device_unregister(data->class_dev);
+err_clear_data:
+ if (coreboot_cfr_data == data)
+ coreboot_cfr_data = NULL;
+ return ret;
+}
+
+static void coreboot_cfr_remove(struct coreboot_device *dev)
+{
+ struct coreboot_cfr_drvdata *data = dev_get_drvdata(&dev->dev);
+
+ coreboot_cfr_unregister_settings(data);
+ sysfs_remove_file(&data->attrs_kset->kobj, &pending_reboot_attr.attr);
+ kset_unregister(data->attrs_kset);
+ device_unregister(data->class_dev);
+ if (coreboot_cfr_data == data)
+ coreboot_cfr_data = NULL;
+}
+
+static const struct coreboot_device_id coreboot_cfr_ids[] = {
+ { .tag = LB_TAG_CFR_ROOT },
+ { }
+};
+MODULE_DEVICE_TABLE(coreboot, coreboot_cfr_ids);
+
+static struct coreboot_driver coreboot_cfr_driver = {
+ .probe = coreboot_cfr_probe,
+ .remove = coreboot_cfr_remove,
+ .drv = {
+ .name = DRIVER_NAME,
+ },
+ .id_table = coreboot_cfr_ids,
+};
+module_coreboot_driver(coreboot_cfr_driver);
+
+MODULE_AUTHOR("Sean Rhodes <sean@starlabs.systems>");
+MODULE_DESCRIPTION("coreboot CFR firmware attributes driver");
+MODULE_LICENSE("GPL");
+MODULE_IMPORT_NS("EFIVAR");
diff --git a/include/linux/coreboot.h b/include/linux/coreboot.h
index 5d40ca7a1d89..d95211fefde8 100644
--- a/include/linux/coreboot.h
+++ b/include/linux/coreboot.h
@@ -12,16 +12,22 @@
#ifndef _LINUX_COREBOOT_H
#define _LINUX_COREBOOT_H
+#include <linux/bits.h>
#include <linux/compiler_attributes.h>
+#include <linux/container_of.h>
+#include <linux/device.h>
#include <linux/stddef.h>
#include <linux/types.h>
+struct module;
+
typedef __aligned(4) u64 cb_u64;
/* List of coreboot entry structures that is used */
#define CB_TAG_FRAMEBUFFER 0x12
#define LB_TAG_CBMEM_ENTRY 0x31
+#define LB_TAG_CFR_ROOT 0x47
/* Generic */
struct coreboot_table_entry {
@@ -87,4 +93,145 @@ struct lb_framebuffer {
#define LB_FRAMEBUFFER_HAS_ORIENTATION(__fb) \
((__fb)->size >= offsetofend(struct lb_framebuffer, orientation))
+#define CFR_VERSION 0
+
+enum cfr_tags {
+ CFR_TAG_OPTION_FORM = 1,
+ CFR_TAG_ENUM_VALUE = 2,
+ CFR_TAG_OPTION_ENUM = 3,
+ CFR_TAG_OPTION_NUMBER = 4,
+ CFR_TAG_OPTION_BOOL = 5,
+ CFR_TAG_OPTION_VARCHAR = 6,
+ CFR_TAG_VARCHAR_OPT_NAME = 7,
+ CFR_TAG_VARCHAR_UI_NAME = 8,
+ CFR_TAG_VARCHAR_UI_HELPTEXT = 9,
+ CFR_TAG_VARCHAR_DEF_VALUE = 10,
+ CFR_TAG_OPTION_COMMENT = 11,
+ CFR_TAG_DEP_VALUES = 12,
+ CFR_TAG_RUNTIME_APPLY = 13,
+};
+
+enum cfr_option_flags {
+ CFR_OPTFLAG_READONLY = BIT(0),
+ CFR_OPTFLAG_INACTIVE = BIT(1),
+ CFR_OPTFLAG_SUPPRESS = BIT(2),
+ CFR_OPTFLAG_VOLATILE = BIT(3),
+ CFR_OPTFLAG_RUNTIME = BIT(4),
+};
+
+struct lb_cfr_varbinary {
+ u32 tag;
+ u32 size;
+ u32 data_length;
+} __packed;
+
+struct lb_cfr_enum_value {
+ u32 tag;
+ u32 size;
+ u32 value;
+} __packed;
+
+enum cfr_runtime_apply_method {
+ CFR_RUNTIME_APPLY_NONE = 0,
+ CFR_RUNTIME_APPLY_APM_CNT = 1,
+};
+
+struct lb_cfr_runtime_apply {
+ u32 tag;
+ u32 size;
+ u32 method;
+ u32 id;
+} __packed;
+
+struct lb_cfr_numeric_option {
+ u32 tag;
+ u32 size;
+ cb_u64 object_id;
+ cb_u64 dependency_id;
+ u32 flags;
+ u32 default_value;
+ u32 min;
+ u32 max;
+ u32 step;
+ u32 display_flags;
+} __packed;
+
+struct lb_cfr_varchar_option {
+ u32 tag;
+ u32 size;
+ cb_u64 object_id;
+ cb_u64 dependency_id;
+ u32 flags;
+} __packed;
+
+struct lb_cfr_option_comment {
+ u32 tag;
+ u32 size;
+ cb_u64 object_id;
+ cb_u64 dependency_id;
+ u32 flags;
+} __packed;
+
+struct lb_cfr_option_form {
+ u32 tag;
+ u32 size;
+ cb_u64 object_id;
+ cb_u64 dependency_id;
+ u32 flags;
+} __packed;
+
+struct lb_cfr {
+ u32 tag;
+ u32 size;
+ u32 version;
+ u32 checksum;
+} __packed;
+
+struct coreboot_device_id;
+struct coreboot_device;
+
+/* A device, additionally with information from coreboot. */
+struct coreboot_device {
+ struct device dev;
+ union {
+ struct coreboot_table_entry entry;
+ struct lb_cbmem_ref cbmem_ref;
+ struct lb_cbmem_entry cbmem_entry;
+ struct lb_framebuffer framebuffer;
+ DECLARE_FLEX_ARRAY(u8, raw);
+ };
+};
+
+static inline struct coreboot_device *dev_to_coreboot_device(struct device *dev)
+{
+ return container_of(dev, struct coreboot_device, dev);
+}
+
+/* A driver for handling devices described in coreboot tables. */
+struct coreboot_driver {
+ int (*probe)(struct coreboot_device *dev);
+ void (*remove)(struct coreboot_device *dev);
+ struct device_driver drv;
+ const struct coreboot_device_id *id_table;
+};
+
+/* use a macro to avoid include chaining to get THIS_MODULE */
+#define coreboot_driver_register(driver) \
+ __coreboot_driver_register(driver, THIS_MODULE)
+/* Register a driver that uses the data from a coreboot table. */
+int __coreboot_driver_register(struct coreboot_driver *driver,
+ struct module *owner);
+
+/* Unregister a driver that uses the data from a coreboot table. */
+void coreboot_driver_unregister(struct coreboot_driver *driver);
+
+/* module_coreboot_driver() - Helper macro for drivers that don't do
+ * anything special in module init/exit. This eliminates a lot of
+ * boilerplate. Each module may only use this macro once, and
+ * calling it replaces module_init() and module_exit()
+ */
+#define module_coreboot_driver(__coreboot_driver) \
+ module_driver(__coreboot_driver, coreboot_driver_register, \
+ coreboot_driver_unregister)
+
#endif /* _LINUX_COREBOOT_H */
^ permalink raw reply related [flat|nested] 4+ messages in thread