[PATCH v5 1/4] firmware: introduce sysfs driver for QEMU's fw_cfg device

Gabriel L. Somlo
2015-11-23T15:57:41Z

From: Gabriel Somlo <somlo@cmu.edu>

Make fw_cfg entries of type "file" available via sysfs. Entries
are listed under /sys/firmware/qemu_fw_cfg/by_key, in folders
named after each entry's selector key. Filename, selector value,
and size read-only attributes are included for each entry. Also,
a "raw" attribute allows retrieval of the full binary content of
each entry.

The fw_cfg device can be instantiated automatically from ACPI or
the Device Tree, or manually by using a kernel module (or command
line) parameter, with a syntax outlined in the documentation file.

Signed-off-by: Gabriel Somlo <somlo@cmu.edu>
---
.../ABI/testing/sysfs-firmware-qemu_fw_cfg | 58 ++
drivers/firmware/Kconfig | 19 +
drivers/firmware/Makefile | 1 +
drivers/firmware/qemu_fw_cfg.c | 611 +++++++++++++++++++++
4 files changed, 689 insertions(+)
create mode 100644 Documentation/ABI/testing/sysfs-firmware-qemu_fw_cfg
create mode 100644 drivers/firmware/qemu_fw_cfg.c

diff --git a/Documentation/ABI/testing/sysfs-firmware-qemu_fw_cfg b/Documentation/ABI/testing/sysfs-firmware-qemu_fw_cfg
new file mode 100644
index 0000000..718fbac
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-firmware-qemu_fw_cfg
@@ -0,0 +1,58 @@
+What: /sys/firmware/qemu_fw_cfg/
+Date: August 2015
+Contact: Gabriel Somlo <somlo@cmu.edu>
+Description:
+ Several different architectures supported by QEMU (x86, arm,
+ sun4*, ppc/mac) are provisioned with a firmware configuration
+ (fw_cfg) device, originally intended as a way for the host to
+ provide configuration data to the guest firmware. Starting
+ with QEMU v2.4, arbitrary fw_cfg file entries may be specified
+ by the user on the command line, which makes fw_cfg additionally
+ useful as an out-of-band, asynchronous mechanism for providing
+ configuration data to the guest userspace.
+
+ The authoritative guest-side hardware interface documentation
+ to the fw_cfg device ca be found in "docs/specs/fw_cfg.txt" in
+ the QEMU source tree.
+
+ === SysFS fw_cfg Interface ===
+
+ The fw_cfg sysfs interface described in this document is only
+ intended to display discoverable blobs (i.e., those registered
+ with the file directory), as there is no way to determine the
+ presence or size of "legacy" blobs (with selector keys between
+ 0x0002 and 0x0018) programmatically.
+
+ All fw_cfg information is shown under:
+
+ /sys/firmware/qemu_fw_cfg/
+
+ The only legacy blob displayed is the fw_cfg device revision:
+
+ /sys/firmware/qemu_fw_cfg/rev
+
+ --- Discoverable fw_cfg blobs by selector key ---
+
+ All discoverable blobs listed in the fw_cfg file directory are
+ displayed as entries named after their unique selector key
+ value, e.g.:
+
+ /sys/firmware/qemu_fw_cfg/by_key/32
+ /sys/firmware/qemu_fw_cfg/by_key/33
+ /sys/firmware/qemu_fw_cfg/by_key/34
+ ...
+
+ Each such fw_cfg sysfs entry has the following values exported
+ as attributes:
+
+ name : The 56-byte nul-terminated ASCII string used as the
+ blob's 'file name' in the fw_cfg directory.
+ size : The length of the blob, as given in the fw_cfg
+ directory.
+ key : The value of the blob's selector key as given in the
+ fw_cfg directory. This value is the same as used in
+ the parent directory name.
+ raw : The raw bytes of the blob, obtained by selecting the
+ entry via the control register, and reading a number
+ of bytes equal to the blob size from the data
+ register.
diff --git a/drivers/firmware/Kconfig b/drivers/firmware/Kconfig
index cf478fe..3cf920a 100644
--- a/drivers/firmware/Kconfig
+++ b/drivers/firmware/Kconfig
@@ -161,6 +161,25 @@ config RASPBERRYPI_FIRMWARE
This option enables support for communicating with the firmware on the
Raspberry Pi.

+config FW_CFG_SYSFS
+ tristate "QEMU fw_cfg device support in sysfs"
+ depends on SYSFS
+ default n
+ help
+ Say Y or M here to enable the exporting of the QEMU firmware
+ configuration (fw_cfg) file entries via sysfs. Entries are
+ found under /sys/firmware/fw_cfg when this option is enabled
+ and loaded.
+
+config FW_CFG_SYSFS_CMDLINE
+ bool "QEMU fw_cfg device parameter parsing"
+ depends on FW_CFG_SYSFS
+ help
+ Allow the qemu_fw_cfg device to be initialized via the kernel
+ command line or using a module parameter.
+ WARNING: Using incorrect parameters (base address in particular)
+ may crash your system.
+
config QCOM_SCM
bool
depends on ARM || ARM64
diff --git a/drivers/firmware/Makefile b/drivers/firmware/Makefile
index 48dd417..474bada 100644
--- a/drivers/firmware/Makefile
+++ b/drivers/firmware/Makefile
@@ -14,6 +14,7 @@ obj-$(CONFIG_ISCSI_IBFT_FIND) += iscsi_ibft_find.o
obj-$(CONFIG_ISCSI_IBFT) += iscsi_ibft.o
obj-$(CONFIG_FIRMWARE_MEMMAP) += memmap.o
obj-$(CONFIG_RASPBERRYPI_FIRMWARE) += raspberrypi.o
+obj-$(CONFIG_FW_CFG_SYSFS) += qemu_fw_cfg.o
obj-$(CONFIG_QCOM_SCM) += qcom_scm.o
obj-$(CONFIG_QCOM_SCM_64) += qcom_scm-64.o
obj-$(CONFIG_QCOM_SCM_32) += qcom_scm-32.o
diff --git a/drivers/firmware/qemu_fw_cfg.c b/drivers/firmware/qemu_fw_cfg.c
new file mode 100644
index 0000000..618304a
--- /dev/null
+++ b/drivers/firmware/qemu_fw_cfg.c
@@ -0,0 +1,611 @@
+/*
+ * drivers/firmware/qemu_fw_cfg.c
+ *
+ * Copyright 2015 Carnegie Mellon University
+ *
+ * Expose entries from QEMU's firmware configuration (fw_cfg) device in
+ * sysfs (read-only, under "/sys/firmware/qemu_fw_cfg/...").
+ *
+ * The fw_cfg device may be instantiated via either an ACPI node (on x86
+ * and select subsets of aarch64), a Device Tree node (on arm), or using
+ * a kernel module (or command line) parameter with the following syntax:
+ *
+ * [fw_cfg.]ioport=<size>@ [:<ctrl_off>:<data_off>]
+ * or
+ * [fw_cfg.]mmio=<size>@ [:<ctrl_off>:<data_off>]
+ *
+ * where:
+ * <size> := size of ioport or mmio range
+ * := physical base address of ioport or mmio range
+ * <ctrl_off> := (optional) offset of control register
+ * <data_off> := (optional) offset of data register
+ *
+ * e.g.:
+ * fw_cfg.ioport=2@0x510:0:1 (the default on x86)
+ * or
+ * fw_cfg.mmio=0xA@0x9020000:8:0 (the default on arm)
+ */
+
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/acpi.h>
+#include <linux/slab.h>
+#include <linux/io.h>
+#include <linux/ioport.h>
+
+MODULE_AUTHOR("Gabriel L. Somlo <somlo@cmu.edu>");
+MODULE_DESCRIPTION("QEMU fw_cfg sysfs support");
+MODULE_LICENSE("GPL");
+
+/* selector key values for "well-known" fw_cfg entries */
+#define FW_CFG_SIGNATURE 0x00
+#define FW_CFG_ID 0x01
+#define FW_CFG_FILE_DIR 0x19
+
+/* size in bytes of fw_cfg signature */
+#define FW_CFG_SIG_SIZE 4
+
+/* fw_cfg "file name" is up to 56 characters (including terminating nul) */
+#define FW_CFG_MAX_FILE_PATH 56
+
+/* fw_cfg file directory entry type */
+struct fw_cfg_file {
+ u32 size;
+ u16 select;
+ u16 reserved;
+ char name[FW_CFG_MAX_FILE_PATH];
+};
+
+/* fw_cfg device i/o register addresses */
+static bool fw_cfg_is_mmio;
+static phys_addr_t fw_cfg_p_base;
+static resource_size_t fw_cfg_p_size;
+static void __iomem *fw_cfg_dev_base;
+static void __iomem *fw_cfg_reg_ctrl;
+static void __iomem *fw_cfg_reg_data;
+
+/* atomic access to fw_cfg device (potentially slow i/o, so using mutex) */
+static DEFINE_MUTEX(fw_cfg_dev_lock);
+
+/* pick appropriate endianness for selector key */
+static inline u16 fw_cfg_sel_endianness(u16 key)
+{
+ return fw_cfg_is_mmio ? cpu_to_be16(key) : cpu_to_le16(key);
+}
+
+/* read chunk of given fw_cfg blob (caller responsible for sanity-check) */
+static inline void fw_cfg_read_blob(u16 key,
+ void *buf, loff_t pos, size_t count)
+{
+ mutex_lock(&fw_cfg_dev_lock);
+ iowrite16(fw_cfg_sel_endianness(key), fw_cfg_reg_ctrl);
+ while (pos-- > 0)
+ ioread8(fw_cfg_reg_data);
+ ioread8_rep(fw_cfg_reg_data, buf, count);
+ mutex_unlock(&fw_cfg_dev_lock);
+}
+
+/* clean up fw_cfg device i/o */
+static void fw_cfg_io_cleanup(void)
+{
+ if (fw_cfg_is_mmio) {
+ iounmap(fw_cfg_dev_base);
+ release_mem_region(fw_cfg_p_base, fw_cfg_p_size);
+ } else {
+ ioport_unmap(fw_cfg_dev_base);
+ release_region(fw_cfg_p_base, fw_cfg_p_size);
+ }
+}
+
+/* initialize fw_cfg device i/o from platform data */
+static int fw_cfg_do_platform_probe(struct platform_device *pdev)
+{
+ char sig[FW_CFG_SIG_SIZE];
+ struct resource *range, *ctrl, *data;
+
+ /* acquire i/o range details */
+ fw_cfg_is_mmio = false;
+ range = platform_get_resource(pdev, IORESOURCE_IO, 0);
+ if (!range) {
+ fw_cfg_is_mmio = true;
+ range = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+ if (!range)
+ return -EINVAL;
+ }
+ fw_cfg_p_base = range->start;
+ fw_cfg_p_size = resource_size(range);
+
+ if (fw_cfg_is_mmio) {
+ if (!request_mem_region(fw_cfg_p_base,
+ fw_cfg_p_size, "fw_cfg_mem"))
+ return -EBUSY;
+ fw_cfg_dev_base = ioremap(fw_cfg_p_base, fw_cfg_p_size);
+ if (!fw_cfg_dev_base) {
+ release_mem_region(fw_cfg_p_base, fw_cfg_p_size);
+ return -EFAULT;
+ }
+ /* set register addresses (using arm/mmio offsets) */
+ fw_cfg_reg_ctrl = fw_cfg_dev_base + 0x08;
+ fw_cfg_reg_data = fw_cfg_dev_base + 0x00;
+ } else {
+ if (!request_region(fw_cfg_p_base,
+ fw_cfg_p_size, "fw_cfg_io"))
+ return -EBUSY;
+ fw_cfg_dev_base = ioport_map(fw_cfg_p_base, fw_cfg_p_size);
+ if (!fw_cfg_dev_base) {
+ release_region(fw_cfg_p_base, fw_cfg_p_size);
+ return -EFAULT;
+ }
+ /* set register addresses (using pc/i386/ioport offsets) */
+ fw_cfg_reg_ctrl = fw_cfg_dev_base + 0x00;
+ fw_cfg_reg_data = fw_cfg_dev_base + 0x01;
+ }
+
+ /* were custom register offsets provided (e.g. on the command line)? */
+ ctrl = platform_get_resource_byname(pdev, IORESOURCE_REG, "ctrl");
+ data = platform_get_resource_byname(pdev, IORESOURCE_REG, "data");
+ if (ctrl && data) {
+ fw_cfg_reg_ctrl = fw_cfg_dev_base + ctrl->start;
+ fw_cfg_reg_data = fw_cfg_dev_base + data->start;
+ }
+
+ /* verify fw_cfg device signature */
+ fw_cfg_read_blob(FW_CFG_SIGNATURE, sig, 0, FW_CFG_SIG_SIZE);
+ if (memcmp(sig, "QEMU", FW_CFG_SIG_SIZE) != 0) {
+ fw_cfg_io_cleanup();
+ return -ENODEV;
+ }
+
+ return 0;
+}
+
+/* fw_cfg revision attribute, in /sys/firmware/qemu_fw_cfg top-level dir. */
+static u32 fw_cfg_rev;
+
+static ssize_t fw_cfg_showrev(struct kobject *k, struct attribute *a, char *buf)
+{
+ return sprintf(buf, "%u\n", fw_cfg_rev);
+}
+
+static const struct {
+ struct attribute attr;
+ ssize_t (*show)(struct kobject *k, struct attribute *a, char *buf);
+} fw_cfg_rev_attr = {
+ .attr = { .name = "rev", .mode = S_IRUSR },
+ .show = fw_cfg_showrev,
+};
+
+/* fw_cfg_sysfs_entry type */
+struct fw_cfg_sysfs_entry {
+ struct kobject kobj;
+ struct fw_cfg_file f;
+ struct list_head list;
+};
+
+/* get fw_cfg_sysfs_entry from kobject member */
+static inline struct fw_cfg_sysfs_entry *to_entry(struct kobject *kobj)
+{
+ return container_of(kobj, struct fw_cfg_sysfs_entry, kobj);
+}
+
+/* fw_cfg_sysfs_attribute type */
+struct fw_cfg_sysfs_attribute {
+ struct attribute attr;
+ ssize_t (*show)(struct fw_cfg_sysfs_entry *entry, char *buf);
+};
+
+/* get fw_cfg_sysfs_attribute from attribute member */
+static inline struct fw_cfg_sysfs_attribute *to_attr(struct attribute *attr)
+{
+ return container_of(attr, struct fw_cfg_sysfs_attribute, attr);
+}
+
+/* global cache of fw_cfg_sysfs_entry objects */
+static LIST_HEAD(fw_cfg_entry_cache);
+
+/* kobjects removed lazily by kernel, mutual exclusion needed */
+static DEFINE_SPINLOCK(fw_cfg_cache_lock);
+
+static inline void fw_cfg_sysfs_cache_enlist(struct fw_cfg_sysfs_entry *entry)
+{
+ spin_lock(&fw_cfg_cache_lock);
+ list_add_tail(&entry->list, &fw_cfg_entry_cache);
+ spin_unlock(&fw_cfg_cache_lock);
+}
+
+static inline void fw_cfg_sysfs_cache_delist(struct fw_cfg_sysfs_entry *entry)
+{
+ spin_lock(&fw_cfg_cache_lock);
+ list_del(&entry->list);
+ spin_unlock(&fw_cfg_cache_lock);
+}
+
+static void fw_cfg_sysfs_cache_cleanup(void)
+{
+ struct fw_cfg_sysfs_entry *entry, *next;
+
+ list_for_each_entry_safe(entry, next, &fw_cfg_entry_cache, list) {
+ /* will end up invoking fw_cfg_sysfs_cache_delist()
+ * via each object's release() method (i.e. destructor)
+ */
+ kobject_put(&entry->kobj);
+ }
+}
+
+/* default_attrs: per-entry attributes and show methods */
+
+#define FW_CFG_SYSFS_ATTR(_attr) \
+struct fw_cfg_sysfs_attribute fw_cfg_sysfs_attr_##_attr = { \
+ .attr = { .name = __stringify(_attr), .mode = S_IRUSR }, \
+ .show = fw_cfg_sysfs_show_##_attr, \
+}
+
+static ssize_t fw_cfg_sysfs_show_size(struct fw_cfg_sysfs_entry *e, char *buf)
+{
+ return sprintf(buf, "%u\n", e->f.size);
+}
+
+static ssize_t fw_cfg_sysfs_show_key(struct fw_cfg_sysfs_entry *e, char *buf)
+{
+ return sprintf(buf, "%u\n", e->f.select);
+}
+
+static ssize_t fw_cfg_sysfs_show_name(struct fw_cfg_sysfs_entry *e, char *buf)
+{
+ return sprintf(buf, "%s\n", e->f.name);
+}
+
+static FW_CFG_SYSFS_ATTR(size);
+static FW_CFG_SYSFS_ATTR(key);
+static FW_CFG_SYSFS_ATTR(name);
+
+static struct attribute *fw_cfg_sysfs_entry_attrs[] = {
+ &fw_cfg_sysfs_attr_size.attr,
+ &fw_cfg_sysfs_attr_key.attr,
+ &fw_cfg_sysfs_attr_name.attr,
+ NULL,
+};
+
+/* sysfs_ops: find fw_cfg_[entry, attribute] and call appropriate show method */
+static ssize_t fw_cfg_sysfs_attr_show(struct kobject *kobj, struct attribute *a,
+ char *buf)
+{
+ struct fw_cfg_sysfs_entry *entry = to_entry(kobj);
+ struct fw_cfg_sysfs_attribute *attr = to_attr(a);
+
+ return attr->show(entry, buf);
+}
+
+static const struct sysfs_ops fw_cfg_sysfs_attr_ops = {
+ .show = fw_cfg_sysfs_attr_show,
+};
+
+/* release: destructor, to be called via kobject_put() */
+static void fw_cfg_sysfs_release_entry(struct kobject *kobj)
+{
+ struct fw_cfg_sysfs_entry *entry = to_entry(kobj);
+
+ fw_cfg_sysfs_cache_delist(entry);
+ kfree(entry);
+}
+
+/* kobj_type: ties together all properties required to register an entry */
+static struct kobj_type fw_cfg_sysfs_entry_ktype = {
+ .default_attrs = fw_cfg_sysfs_entry_attrs,
+ .sysfs_ops = &fw_cfg_sysfs_attr_ops,
+ .release = fw_cfg_sysfs_release_entry,
+};
+
+/* raw-read method and attribute */
+static ssize_t fw_cfg_sysfs_read_raw(struct file *filp, struct kobject *kobj,
+ struct bin_attribute *bin_attr,
+ char *buf, loff_t pos, size_t count)
+{
+ struct fw_cfg_sysfs_entry *entry = to_entry(kobj);
+
+ if (pos > entry->f.size)
+ return -EINVAL;
+
+ if (count > entry->f.size - pos)
+ count = entry->f.size - pos;
+
+ fw_cfg_read_blob(entry->f.select, buf, pos, count);
+ return count;
+}
+
+static struct bin_attribute fw_cfg_sysfs_attr_raw = {
+ .attr = { .name = "raw", .mode = S_IRUSR },
+ .read = fw_cfg_sysfs_read_raw,
+};
+
+/* kobjects representing top-level and by_key folders */
+static struct kobject *fw_cfg_top_ko;
+static struct kobject *fw_cfg_sel_ko;
+
+/* register an individual fw_cfg file */
+static int fw_cfg_register_file(const struct fw_cfg_file *f)
+{
+ int err;
+ struct fw_cfg_sysfs_entry *entry;
+
+ /* allocate new entry */
+ entry = kzalloc(sizeof(*entry), GFP_KERNEL);
+ if (!entry)
+ return -ENOMEM;
+
+ /* set file entry information */
+ memcpy(&entry->f, f, sizeof(struct fw_cfg_file));
+
+ /* register entry under "/sys/firmware/qemu_fw_cfg/by_key/" */
+ err = kobject_init_and_add(&entry->kobj, &fw_cfg_sysfs_entry_ktype,
+ fw_cfg_sel_ko, "%d", entry->f.select);
+ if (err)
+ goto err_register;
+
+ /* add raw binary content access */
+ err = sysfs_create_bin_file(&entry->kobj, &fw_cfg_sysfs_attr_raw);
+ if (err)
+ goto err_add_raw;
+
+ /* success, add entry to global cache */
+ fw_cfg_sysfs_cache_enlist(entry);
+ return 0;
+
+err_add_raw:
+ kobject_del(&entry->kobj);
+err_register:
+ kfree(entry);
+ return err;
+}
+
+/* iterate over all fw_cfg directory entries, registering each one */
+static int fw_cfg_register_dir_entries(void)
+{
+ int ret = 0;
+ u32 count, i;
+ struct fw_cfg_file *dir;
+ size_t dir_size;
+
+ fw_cfg_read_blob(FW_CFG_FILE_DIR, &count, 0, sizeof(count));
+ count = be32_to_cpu(count);
+ dir_size = count * sizeof(struct fw_cfg_file);
+
+ dir = kmalloc(dir_size, GFP_KERNEL);
+ if (!dir)
+ return -ENOMEM;
+
+ fw_cfg_read_blob(FW_CFG_FILE_DIR, dir, sizeof(count), dir_size);
+
+ for (i = 0; i < count; i++) {
+ dir[i].size = be32_to_cpu(dir[i].size);
+ dir[i].select = be16_to_cpu(dir[i].select);
+ ret = fw_cfg_register_file(&dir[i]);
+ if (ret)
+ break;
+ }
+
+ kfree(dir);
+ return ret;
+}
+
+/* unregister top-level or by_key folder */
+static inline void fw_cfg_kobj_cleanup(struct kobject *kobj)
+{
+ kobject_del(kobj);
+ kobject_put(kobj);
+}
+
+static int fw_cfg_sysfs_probe(struct platform_device *pdev)
+{
+ int err;
+
+ /* NOTE: If we supported multiple fw_cfg devices, we'd first create
+ * a subdirectory named after e.g. pdev->id, then hang per-device
+ * by_key subdirectories underneath it. However, only
+ * one fw_cfg device exist system-wide, so if one was already found
+ * earlier, we might as well stop here.
+ */
+ if (fw_cfg_sel_ko)
+ return -EBUSY;
+
+ /* create by_key subdirectory of /sys/firmware/qemu_fw_cfg/ */
+ err = -ENOMEM;
+ fw_cfg_sel_ko = kobject_create_and_add("by_key", fw_cfg_top_ko);
+ if (!fw_cfg_sel_ko)
+ goto err_sel;
+
+ /* initialize fw_cfg device i/o from platform data */
+ err = fw_cfg_do_platform_probe(pdev);
+ if (err)
+ goto err_probe;
+
+ /* get revision number, add matching top-level attribute */
+ fw_cfg_read_blob(FW_CFG_ID, &fw_cfg_rev, 0, sizeof(fw_cfg_rev));
+ fw_cfg_rev = le32_to_cpu(fw_cfg_rev);
+ err = sysfs_create_file(fw_cfg_top_ko, &fw_cfg_rev_attr.attr);
+ if (err)
+ goto err_rev;
+
+ /* process fw_cfg file directory entry, registering each file */
+ err = fw_cfg_register_dir_entries();
+ if (err)
+ goto err_dir;
+
+ /* success */
+ pr_debug("fw_cfg: loaded.\n");
+ return 0;
+
+err_dir:
+ fw_cfg_sysfs_cache_cleanup();
+ sysfs_remove_file(fw_cfg_top_ko, &fw_cfg_rev_attr.attr);
+err_rev:
+ fw_cfg_io_cleanup();
+err_probe:
+ fw_cfg_kobj_cleanup(fw_cfg_sel_ko);
+err_sel:
+ return err;
+}
+
+static int fw_cfg_sysfs_remove(struct platform_device *pdev)
+{
+ pr_debug("fw_cfg: unloading.\n");
+ fw_cfg_sysfs_cache_cleanup();
+ fw_cfg_kobj_cleanup(fw_cfg_sel_ko);
+ fw_cfg_io_cleanup();
+ return 0;
+}
+
+static const struct of_device_id fw_cfg_sysfs_mmio_match[] = {
+ { .compatible = "qemu,fw-cfg-mmio", },
+ {},
+};
+MODULE_DEVICE_TABLE(of, fw_cfg_sysfs_mmio_match);
+
+#ifdef CONFIG_ACPI
+static const struct acpi_device_id fw_cfg_sysfs_acpi_match[] = {
+ { "QEMU0002", },
+ {},
+};
+MODULE_DEVICE_TABLE(acpi, fw_cfg_sysfs_acpi_match);
+#endif
+
+static struct platform_driver fw_cfg_sysfs_driver = {
+ .probe = fw_cfg_sysfs_probe,
+ .remove = fw_cfg_sysfs_remove,
+ .driver = {
+ .name = "fw_cfg",
+ .of_match_table = fw_cfg_sysfs_mmio_match,
+ .acpi_match_table = ACPI_PTR(fw_cfg_sysfs_acpi_match),
+ },
+};
+
+#ifdef CONFIG_FW_CFG_SYSFS_CMDLINE
+
+static struct platform_device *fw_cfg_cmdline_dev;
+
+static int fw_cfg_cmdline_set(const char *arg, const struct kernel_param *kp)
+{
+ struct resource res[3] = {};
+ char *str;
+ phys_addr_t base;
+ resource_size_t size, ctrl_off, data_off;
+ int processed, consumed = 0;
+
+ /* only one fw_cfg device can exist system-wide, so if one
+ * was processed on the command line already, we might as
+ * well stop here.
+ */
+ if (fw_cfg_cmdline_dev) {
+ /* avoid leaking previously registered device */
+ platform_device_unregister(fw_cfg_cmdline_dev);
+ return -EINVAL;
+ }
+
+ /* consume "<size>" portion of command line argument */
+ size = memparse(arg, &str);
+
+ /* get "@ [:<ctrl_off>:<data_off>]" chunks */
+ processed = sscanf(str, "@%lli%n:%lli:%lli%n",
+ &base, &consumed,
+ &ctrl_off, &data_off, &consumed);
+
+ /* sscanf() must process precisely 1 or 3 chunks:
+ * is mandatory, optionally followed by <ctrl_off>
+ * and <data_off>;
+ * there must be no extra characters after the last chunk,
+ * so str[consumed] must be '\0'.
+ */
+ if (str[consumed] ||
+ (processed != 1 && processed != 3))
+ return -EINVAL;
+
+ res[0].start = base;
+ res[0].end = base + size - 1;
+ res[0].flags = !strcmp(kp->name, "mmio") ? IORESOURCE_MEM :
+ IORESOURCE_IO;
+
+ /* insert register offsets, if provided */
+ if (processed > 1) {
+ res[1].name = "ctrl";
+ res[1].start = ctrl_off;
+ res[1].flags = IORESOURCE_REG;
+ res[2].name = "data";
+ res[2].start = data_off;
+ res[2].flags = IORESOURCE_REG;
+ }
+
+ /* "processed" happens to nicely match the number of resources
+ * we need to pass in to this platform device.
+ */
+ fw_cfg_cmdline_dev = platform_device_register_simple("fw_cfg",
+ PLATFORM_DEVID_NONE, res, processed);
+ if (IS_ERR(fw_cfg_cmdline_dev))
+ return PTR_ERR(fw_cfg_cmdline_dev);
+
+ return 0;
+}
+
+static int fw_cfg_cmdline_get(char *buf, const struct kernel_param *kp)
+{
+ /* stay silent if device was not configured via the command
+ * line, or if the parameter name (ioport/mmio) doesn't match
+ * the device setting
+ */
+ if (!fw_cfg_cmdline_dev ||
+ (!strcmp(kp->name, "mmio") ^
+ (fw_cfg_cmdline_dev->resource[0].flags == IORESOURCE_MEM)))
+ return 0;
+
+ switch (fw_cfg_cmdline_dev->num_resources) {
+ case 1:
+ return snprintf(buf, PAGE_SIZE, "0x%llx@0x%llx",
+ resource_size(&fw_cfg_cmdline_dev->resource[0]),
+ fw_cfg_cmdline_dev->resource[0].start);
+ case 3:
+ return snprintf(buf, PAGE_SIZE, "0x%llx@0x%llx:%llu:%llu",
+ resource_size(&fw_cfg_cmdline_dev->resource[0]),
+ fw_cfg_cmdline_dev->resource[0].start,
+ fw_cfg_cmdline_dev->resource[1].start,
+ fw_cfg_cmdline_dev->resource[2].start);
+ }
+
+ /* Should never get here */
+ WARN(1, "Unexpected number of resources: %d\n",
+ fw_cfg_cmdline_dev->num_resources);
+ return 0;
+}
+
+static const struct kernel_param_ops fw_cfg_cmdline_param_ops = {
+ .set = fw_cfg_cmdline_set,
+ .get = fw_cfg_cmdline_get,
+};
+
+device_param_cb(ioport, &fw_cfg_cmdline_param_ops, NULL, S_IRUSR);
+device_param_cb(mmio, &fw_cfg_cmdline_param_ops, NULL, S_IRUSR);
+
+#endif /* CONFIG_FW_CFG_SYSFS_CMDLINE */
+
+static int __init fw_cfg_sysfs_init(void)
+{
+ /* create /sys/firmware/qemu_fw_cfg/ top level directory */
+ fw_cfg_top_ko = kobject_create_and_add("qemu_fw_cfg", firmware_kobj);
+ if (!fw_cfg_top_ko)
+ return -ENOMEM;
+
+ return platform_driver_register(&fw_cfg_sysfs_driver);
+}
+
+static void __exit fw_cfg_sysfs_exit(void)
+{
+ platform_driver_unregister(&fw_cfg_sysfs_driver);
+
+#ifdef CONFIG_FW_CFG_SYSFS_CMDLINE
+ platform_device_unregister(fw_cfg_cmdline_dev);
+#endif
+
+ /* clean up /sys/firmware/qemu_fw_cfg/ */
+ fw_cfg_kobj_cleanup(fw_cfg_top_ko);
+}
+
+module_init(fw_cfg_sysfs_init);
+module_exit(fw_cfg_sysfs_exit);
--
2.4.3