platform/x86: wmi-bmof: New driver to expose embedded Binary WMI MOF metadata

Many laptops (and maybe servers?) have embedded WMI Binary MOF metadata.
We do not yet have open-source tools for processing the data, although
one is in the works thanks to Pali:

	https://github.com/pali/bmfdec

There is currently no interface to get the data in the first place. By
exposing it, we facilitate the development of new tools.

This is based on the original work of Andy Lutomirski <luto@kernel.org>,
but contains several modifications in response to various reviews.

Signed-off-by: Darren Hart (VMware) <dvhart@infradead.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Mario Limonciello <mario_limonciello@dell.com>
Cc: Pali Rohár <pali.rohar@gmail.com>
Cc: linux-kernel@vger.kernel.org
Cc: platform-driver-x86@vger.kernel.org
Cc: linux-acpi@vger.kernel.org
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>

1 files changed, 124 insertions, 0 deletions

diff --git a/drivers/platform/x86/wmi-bmof.c b/drivers/platform/x86/wmi-bmof.c
new file mode 100644
index 000000000000..94922b9342ce
--- /dev/null
+++ b/drivers/platform/x86/wmi-bmof.c
@@ -0,0 +1,124 @@
+/*
+ * WMI embedded Binary MOF driver
+ *
+ * Copyright (c) 2015 Andrew Lutomirski
+ *
+ *  This program is free software; you can redistribute it and/or modify it
+ *  under the terms of the GNU General Public License version 2 as published
+ *  by the Free Software Foundation.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/acpi.h>
+#include <linux/device.h>
+#include <linux/fs.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/string.h>
+#include <linux/sysfs.h>
+#include <linux/types.h>
+#include <linux/wmi.h>
+
+#define WMI_BMOF_GUID "05901221-D566-11D1-B2F0-00A0C9062910"
+
+struct bmof_priv {
+	union acpi_object *bmofdata;
+	struct bin_attribute bmof_bin_attr;
+};
+
+static ssize_t
+read_bmof(struct file *filp, struct kobject *kobj,
+	 struct bin_attribute *attr,
+	 char *buf, loff_t off, size_t count)
+{
+	struct bmof_priv *priv =
+		container_of(attr, struct bmof_priv, bmof_bin_attr);
+
+	if (off < 0)
+		return -EINVAL;
+
+	if (off >= priv->bmofdata->buffer.length)
+		return 0;
+
+	if (count > priv->bmofdata->buffer.length - off)
+		count = priv->bmofdata->buffer.length - off;
+
+	memcpy(buf, priv->bmofdata->buffer.pointer + off, count);
+	return count;
+}
+
+static int wmi_bmof_probe(struct wmi_device *wdev)
+{
+	struct bmof_priv *priv;
+	int ret;
+
+	priv = devm_kzalloc(&wdev->dev, sizeof(struct bmof_priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	dev_set_drvdata(&wdev->dev, priv);
+
+	priv->bmofdata = wmidev_block_query(wdev, 0);
+	if (!priv->bmofdata) {
+		dev_err(&wdev->dev, "failed to read Binary MOF\n");
+		return -EIO;
+	}
+
+	if (priv->bmofdata->type != ACPI_TYPE_BUFFER) {
+		dev_err(&wdev->dev, "Binary MOF is not a buffer\n");
+		ret = -EIO;
+		goto err_free;
+	}
+
+	sysfs_bin_attr_init(&priv->bmof_bin_attr);
+	priv->bmof_bin_attr.attr.name = "bmof";
+	priv->bmof_bin_attr.attr.mode = 0400;
+	priv->bmof_bin_attr.read = read_bmof;
+	priv->bmof_bin_attr.size = priv->bmofdata->buffer.length;
+
+	ret = sysfs_create_bin_file(&wdev->dev.kobj, &priv->bmof_bin_attr);
+	if (ret)
+		goto err_free;
+
+	return 0;
+
+ err_free:
+	kfree(priv->bmofdata);
+	return ret;
+}
+
+static int wmi_bmof_remove(struct wmi_device *wdev)
+{
+	struct bmof_priv *priv = dev_get_drvdata(&wdev->dev);
+
+	sysfs_remove_bin_file(&wdev->dev.kobj, &priv->bmof_bin_attr);
+	kfree(priv->bmofdata);
+	return 0;
+}
+
+static const struct wmi_device_id wmi_bmof_id_table[] = {
+	{ .guid_string = WMI_BMOF_GUID },
+	{ },
+};
+
+static struct wmi_driver wmi_bmof_driver = {
+	.driver = {
+		.name = "wmi-bmof",
+	},
+	.probe = wmi_bmof_probe,
+	.remove = wmi_bmof_remove,
+	.id_table = wmi_bmof_id_table,
+};
+
+module_wmi_driver(wmi_bmof_driver);
+
+MODULE_ALIAS("wmi:" WMI_BMOF_GUID);
+MODULE_AUTHOR("Andrew Lutomirski <luto@kernel.org>");
+MODULE_DESCRIPTION("WMI embedded Binary MOF driver");
+MODULE_LICENSE("GPL");