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    SubjectRe: [PATCH v8 1/4] firmware: introduce sysfs driver for QEMU's fw_cfg device
    On Thu, Jan 28, 2016 at 09:23:11AM -0500, Gabriel L. Somlo wrote:
    > 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 | 648 +++++++++++++++++++++
    > 4 files changed, 726 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..e9e58d4
    > --- /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 can 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 49a3a11..5130f74 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 && (ARM || ARM64 || PPC_PMAC || SPARC || X86)
    > + 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..83e8a5c
    > --- /dev/null
    > +++ b/drivers/firmware/qemu_fw_cfg.c
    > @@ -0,0 +1,648 @@
    > +/*
    > + * 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>@<base>[:<ctrl_off>:<data_off>]
    > + * or
    > + * [fw_cfg.]mmio=<size>@<base>[:<ctrl_off>:<data_off>]
    > + *
    > + * where:
    > + * <size> := size of ioport or mmio range
    > + * <base> := 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);
    > +}

    This locking is not enough I think: ACPI might be
    accessing FW CFG meanwhile, and assuming it's
    the only owner.

    I think that on systems that support ACPI,
    it would be better to use an ACPI interface
    to read blobs, instead of poking on _CRS and banging on registers directly.

    This will also make it easier to extend the interface,
    and support DMA.



    > +
    > +/* 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);
    > + }
    > +}
    > +
    > +/* arch-specific ctrl & data register offsets are not available in ACPI, DT */

    So for all arches which support ACPI, I think this driver
    should just rely on ACPI.

    > +#if !(defined(FW_CFG_CTRL_OFF) && defined(FW_CTRL_DATA_OFF))
    > +# if (defined(CONFIG_ARM) || defined(CONFIG_ARM64))
    > +# define FW_CFG_CTRL_OFF 0x08
    > +# define FW_CFG_DATA_OFF 0x00
    > +# elif (defined(CONFIG_PPC_PMAC) || defined(CONFIG_SPARC32)) /* ppc/mac,sun4m */
    > +# define FW_CFG_CTRL_OFF 0x00
    > +# define FW_CFG_DATA_OFF 0x02
    > +# elif (defined(CONFIG_X86) || defined(CONFIG_SPARC64)) /* x86, sun4u */
    > +# define FW_CFG_CTRL_OFF 0x00
    > +# define FW_CFG_DATA_OFF 0x01
    > +# else
    > +# warning "QEMU FW_CFG may not be available on this architecture!"
    > +# define FW_CFG_CTRL_OFF 0x00
    > +# define FW_CFG_DATA_OFF 0x01

    Better not try hacks like this, they are hard
    to support down the road. Please only list what is tested and
    actually exposed by QEMU.


    > +# endif
    > +#endif
    > +
    > +/* 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;
    > + }
    > + } 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;
    > + }
    > + }
    > +
    > + /* 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;
    > + } else {
    > + /* use architecture-specific offsets */
    > + fw_cfg_reg_ctrl = fw_cfg_dev_base + FW_CFG_CTRL_OFF;
    > + fw_cfg_reg_data = fw_cfg_dev_base + FW_CFG_DATA_OFF;
    > + }
    > +
    > + /* 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;
    > +
    > +/* this probably belongs in e.g. include/linux/types.h,
    > + * but right now we are the only ones doing it...
    > + */
    > +#ifdef CONFIG_PHYS_ADDR_T_64BIT
    > +#define __PHYS_ADDR_PREFIX "ll"
    > +#else
    > +#define __PHYS_ADDR_PREFIX ""
    > +#endif
    > +
    > +/* use special scanf/printf modifier for phys_addr_t, resource_size_t */
    > +#define PH_ADDR_SCAN_FMT "@%" __PHYS_ADDR_PREFIX "i%n" \
    > + ":%" __PHYS_ADDR_PREFIX "i" \
    > + ":%" __PHYS_ADDR_PREFIX "i%n"
    > +
    > +#define PH_ADDR_PR_1_FMT "0x%" __PHYS_ADDR_PREFIX "x@" \
    > + "0x%" __PHYS_ADDR_PREFIX "x"
    > +
    > +#define PH_ADDR_PR_3_FMT PH_ADDR_PR_1_FMT \
    > + ":%" __PHYS_ADDR_PREFIX "u" \
    > + ":%" __PHYS_ADDR_PREFIX "u"
    > +
    > +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 "@<base>[:<ctrl_off>:<data_off>]" chunks */
    > + processed = sscanf(str, PH_ADDR_SCAN_FMT,
    > + &base, &consumed,
    > + &ctrl_off, &data_off, &consumed);
    > +
    > + /* sscanf() must process precisely 1 or 3 chunks:
    > + * <base> 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, PH_ADDR_PR_1_FMT,
    > + resource_size(&fw_cfg_cmdline_dev->resource[0]),
    > + fw_cfg_cmdline_dev->resource[0].start);
    > + case 3:
    > + return snprintf(buf, PAGE_SIZE, PH_ADDR_PR_3_FMT,
    > + 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

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