DMI-based module autoloading

The patch below adds DMI/SMBIOS based module autoloading to the Linux
kernel. The idea is to load laptop drivers automatically (and other
drivers which cannot be autoloaded otherwise), based on the DMI system
identification information of the BIOS.

Right now most distros manually try to load all available laptop
drivers on bootup in the hope that at least one of them loads
successfully. This patch does away with all that, and uses udev to
automatically load matching drivers on the right machines.

Basically the patch just exports the DMI information that has been
parsed by the kernel anyway to userspace via a sysfs device
/sys/class/dmi/id and makes sure that proper modalias attributes are
available. Besides adding the "modalias" attribute it also adds
attributes for a few other DMI fields which might be useful for
writing udev rules.

This patch is not an attempt to export the entire DMI/SMBIOS data to
userspace. We already have "dmidecode" which parses the complete DMI
info from userspace. The purpose of this patch is machine model
identification and good udev integration.

To take advantage of DMI based module autoloading, a driver should
export one or more MODULE_ALIAS fields similar to these:

MODULE_ALIAS("dmi:*:svnMICRO-STARINT'LCO.,LTD:pnMS-1013:pvr0131*:cvnMICRO-STARINT'LCO.,LTD:ct10:*");
MODULE_ALIAS("dmi:*:svnMicro-StarInternational:pnMS-1058:pvr0581:rvnMSI:rnMS-1058:*:ct10:*");
MODULE_ALIAS("dmi:*:svnMicro-StarInternational:pnMS-1412:*:rvnMSI:rnMS-1412:*:cvnMICRO-STARINT'LCO.,LTD:ct10:*");
MODULE_ALIAS("dmi:*:svnNOTEBOOK:pnSAM2000:pvr0131*:cvnMICRO-STARINT'LCO.,LTD:ct10:*");

These lines are specific to my msi-laptop.c driver. They are basically
just a concatenation of a few carefully selected DMI fields with all
potentially bad characters stripped.

Besides laptop drivers, modules like "hdaps", the i2c modules
and the hwmon modules are good candidates for "dmi:" MODULE_ALIAS
lines.

Besides merely exporting the DMI data via sysfs the patch adds
support for a few more DMI fields. Especially the CHASSIS fields are
very useful to identify different laptop modules. The patch also adds
working MODULE_ALIAS lines to my msi-laptop.c driver.

I'd like to thank Kay Sievers for helping me to clean up this patch
for posting it on lkml.

Patch is against Linus' current GIT HEAD. Should probably apply to
older kernels as well without modification.


Signed-off-by: Lennart Poettering <mzxreary@0pointer.de>
Signed-off-by: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 222 insertions, 0 deletions

diff --git a/drivers/firmware/dmi-id.c b/drivers/firmware/dmi-id.c
new file mode 100644
index 000000000000..59c3b5aa89f4
--- /dev/null
+++ b/drivers/firmware/dmi-id.c
@@ -0,0 +1,222 @@
+/*
+ * Export SMBIOS/DMI info via sysfs to userspace
+ *
+ * Copyright 2007, Lennart Poettering
+ *
+ * Licensed under GPLv2
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/dmi.h>
+#include <linux/device.h>
+#include <linux/autoconf.h>
+
+#define DEFINE_DMI_ATTR(_name, _mode, _show)            \
+static struct device_attribute sys_dmi_##_name##_attr = \
+        __ATTR(_name, _mode, _show, NULL);
+
+#define DEFINE_DMI_ATTR_WITH_SHOW(_name, _mode, _field)                 \
+static ssize_t sys_dmi_##_name##_show(struct device *dev,               \
+                                      struct device_attribute *attr,    \
+                                      char *page)                       \
+{                                                                       \
+        ssize_t len;                                                    \
+        len = scnprintf(page, PAGE_SIZE, "%s\n", dmi_get_system_info(_field)); \
+        page[len-1] = '\n';                                             \
+        return len;                                                     \
+}                                                                       \
+DEFINE_DMI_ATTR(_name, _mode, sys_dmi_##_name##_show);
+
+DEFINE_DMI_ATTR_WITH_SHOW(bios_vendor,          0444, DMI_BIOS_VENDOR);
+DEFINE_DMI_ATTR_WITH_SHOW(bios_version,         0444, DMI_BIOS_VERSION);
+DEFINE_DMI_ATTR_WITH_SHOW(bios_date,            0444, DMI_BIOS_DATE);
+DEFINE_DMI_ATTR_WITH_SHOW(sys_vendor,           0444, DMI_SYS_VENDOR);
+DEFINE_DMI_ATTR_WITH_SHOW(product_name,         0444, DMI_PRODUCT_NAME);
+DEFINE_DMI_ATTR_WITH_SHOW(product_version,      0444, DMI_PRODUCT_VERSION);
+DEFINE_DMI_ATTR_WITH_SHOW(product_serial,       0400, DMI_PRODUCT_SERIAL);
+DEFINE_DMI_ATTR_WITH_SHOW(product_uuid,         0400, DMI_PRODUCT_UUID);
+DEFINE_DMI_ATTR_WITH_SHOW(board_vendor,         0444, DMI_BOARD_VENDOR);
+DEFINE_DMI_ATTR_WITH_SHOW(board_name,           0444, DMI_BOARD_NAME);
+DEFINE_DMI_ATTR_WITH_SHOW(board_version,        0444, DMI_BOARD_VERSION);
+DEFINE_DMI_ATTR_WITH_SHOW(board_serial,         0400, DMI_BOARD_SERIAL);
+DEFINE_DMI_ATTR_WITH_SHOW(board_asset_tag,      0444, DMI_BOARD_ASSET_TAG);
+DEFINE_DMI_ATTR_WITH_SHOW(chassis_vendor,       0444, DMI_CHASSIS_VENDOR);
+DEFINE_DMI_ATTR_WITH_SHOW(chassis_type,         0444, DMI_CHASSIS_TYPE);
+DEFINE_DMI_ATTR_WITH_SHOW(chassis_version,      0444, DMI_CHASSIS_VERSION);
+DEFINE_DMI_ATTR_WITH_SHOW(chassis_serial,       0400, DMI_CHASSIS_SERIAL);
+DEFINE_DMI_ATTR_WITH_SHOW(chassis_asset_tag,    0444, DMI_CHASSIS_ASSET_TAG);
+
+static void ascii_filter(char *d, const char *s)
+{
+        /* Filter out characters we don't want to see in the modalias string */
+        for (; *s; s++)
+                if (*s > ' ' && *s < 127 && *s != ':')
+                        *(d++) = *s;
+
+        *d = 0;
+}
+
+static ssize_t get_modalias(char *buffer, size_t buffer_size)
+{
+        static const struct mafield {
+                const char *prefix;
+                int field;
+        } fields[] = {
+                { "bvn", DMI_BIOS_VENDOR },
+                { "bvr", DMI_BIOS_VERSION },
+                { "bd",  DMI_BIOS_DATE },
+                { "svn", DMI_SYS_VENDOR },
+                { "pn",  DMI_PRODUCT_NAME },
+                { "pvr", DMI_PRODUCT_VERSION },
+                { "rvn", DMI_BOARD_VENDOR },
+                { "rn",  DMI_BOARD_NAME },
+                { "rvr", DMI_BOARD_VERSION },
+                { "cvn", DMI_CHASSIS_VENDOR },
+                { "ct",  DMI_CHASSIS_TYPE },
+                { "cvr", DMI_CHASSIS_VERSION },
+                { NULL,  DMI_NONE }
+        };
+
+        ssize_t l, left;
+        char *p;
+        const struct mafield *f;
+
+        strcpy(buffer, "dmi");
+        p = buffer + 3; left = buffer_size - 4;
+
+        for (f = fields; f->prefix && left > 0; f++) {
+                const char *c;
+                char *t;
+
+                c = dmi_get_system_info(f->field);
+                if (!c)
+                        continue;
+
+                t = kmalloc(strlen(c) + 1, GFP_KERNEL);
+                if (!t)
+                        break;
+                ascii_filter(t, c);
+                l = scnprintf(p, left, ":%s%s", f->prefix, t);
+                kfree(t);
+
+                p += l;
+                left -= l;
+        }
+
+        p[0] = ':';
+        p[1] = 0;
+
+        return p - buffer + 1;
+}
+
+static ssize_t sys_dmi_modalias_show(struct device *dev,
+                                     struct device_attribute *attr, char *page)
+{
+        ssize_t r;
+        r = get_modalias(page, PAGE_SIZE-1);
+        page[r] = '\n';
+        page[r+1] = 0;
+        return r+1;
+}
+
+DEFINE_DMI_ATTR(modalias, 0444, sys_dmi_modalias_show);
+
+static struct attribute *sys_dmi_attributes[DMI_STRING_MAX+2];
+
+static struct attribute_group sys_dmi_attribute_group = {
+        .attrs = sys_dmi_attributes,
+};
+
+static struct attribute_group* sys_dmi_attribute_groups[] = {
+        &sys_dmi_attribute_group,
+        NULL
+};
+
+static int dmi_dev_uevent(struct device *dev, char **envp,
+                            int num_envp, char *buffer, int buffer_size)
+{
+        strcpy(buffer, "MODALIAS=");
+        get_modalias(buffer+9, buffer_size-9);
+        envp[0] = buffer;
+        envp[1] = NULL;
+
+        return 0;
+}
+
+static struct class dmi_class = {
+        .name = "dmi",
+        .dev_release = (void(*)(struct device *)) kfree,
+        .dev_uevent = dmi_dev_uevent,
+};
+
+static struct device *dmi_dev;
+
+/* Initialization */
+
+#define ADD_DMI_ATTR(_name, _field) \
+        if (dmi_get_system_info(_field)) \
+                sys_dmi_attributes[i++] = & sys_dmi_##_name##_attr.attr;
+
+extern int dmi_available;
+
+static int __init dmi_id_init(void)
+{
+        int ret, i;
+
+        if (!dmi_available)
+                return -ENODEV;
+
+        /* Not necessarily all DMI fields are available on all
+         * systems, hence let's built an attribute table of just
+         * what's available */
+        i = 0;
+        ADD_DMI_ATTR(bios_vendor,       DMI_BIOS_VENDOR);
+        ADD_DMI_ATTR(bios_version,      DMI_BIOS_VERSION);
+        ADD_DMI_ATTR(bios_date,         DMI_BIOS_DATE);
+        ADD_DMI_ATTR(sys_vendor,        DMI_SYS_VENDOR);
+        ADD_DMI_ATTR(product_name,      DMI_PRODUCT_NAME);
+        ADD_DMI_ATTR(product_version,   DMI_PRODUCT_VERSION);
+        ADD_DMI_ATTR(product_serial,    DMI_PRODUCT_SERIAL);
+        ADD_DMI_ATTR(product_uuid,      DMI_PRODUCT_UUID);
+        ADD_DMI_ATTR(board_vendor,      DMI_BOARD_VENDOR);
+        ADD_DMI_ATTR(board_name,        DMI_BOARD_NAME);
+        ADD_DMI_ATTR(board_version,     DMI_BOARD_VERSION);
+        ADD_DMI_ATTR(board_serial,      DMI_BOARD_SERIAL);
+        ADD_DMI_ATTR(board_asset_tag,   DMI_BOARD_ASSET_TAG);
+        ADD_DMI_ATTR(chassis_vendor,    DMI_CHASSIS_VENDOR);
+        ADD_DMI_ATTR(chassis_type,      DMI_CHASSIS_TYPE);
+        ADD_DMI_ATTR(chassis_version,   DMI_CHASSIS_VERSION);
+        ADD_DMI_ATTR(chassis_serial,    DMI_CHASSIS_SERIAL);
+        ADD_DMI_ATTR(chassis_asset_tag, DMI_CHASSIS_ASSET_TAG);
+        sys_dmi_attributes[i++] = &sys_dmi_modalias_attr.attr;
+
+        ret = class_register(&dmi_class);
+        if (ret)
+                return ret;
+
+        dmi_dev = kzalloc(sizeof(*dmi_dev), GFP_KERNEL);
+        if (!dmi_dev) {
+                ret = -ENOMEM;
+                goto fail_class_unregister;
+        }
+
+        dmi_dev->class = &dmi_class;
+        strcpy(dmi_dev->bus_id, "id");
+        dmi_dev->groups = sys_dmi_attribute_groups;
+
+        ret = device_register(dmi_dev);
+        if (ret)
+                goto fail_class_unregister;
+
+        return 0;
+
+fail_class_unregister:
+
+        class_unregister(&dmi_class);
+
+        return ret;
+}
+
+arch_initcall(dmi_id_init);