fw_cfg: add a public uapi header

Create a common header file for well-known values and structures to be
shared by the Linux kernel with qemu or other projects.

It is based from qemu/docs/specs/fw_cfg.txt which references
qemu/include/hw/nvram/fw_cfg_keys.h "for the most up-to-date and
authoritative list" & vmcoreinfo.txt. Those files don't have an
explicit license, but qemu/hw/nvram/fw_cfg.c is BSD-license, so
Michael S. Tsirkin suggested to use the same license.

The patch intentionally left out DMA & vmcoreinfo structures &
defines, which are added in the commits making usage of it.

Suggested-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 66 insertions, 0 deletions

diff --git a/include/uapi/linux/qemu_fw_cfg.h b/include/uapi/linux/qemu_fw_cfg.h
new file mode 100644
index 000000000000..c698ac3812f6
--- /dev/null
+++ b/include/uapi/linux/qemu_fw_cfg.h
@@ -0,0 +1,66 @@
+/* SPDX-License-Identifier: BSD-3-Clause */
+#ifndef _LINUX_FW_CFG_H
+#define _LINUX_FW_CFG_H
+
+#include <linux/types.h>
+
+#define FW_CFG_ACPI_DEVICE_ID   "QEMU0002"
+
+/* selector key values for "well-known" fw_cfg entries */
+#define FW_CFG_SIGNATURE        0x00
+#define FW_CFG_ID               0x01
+#define FW_CFG_UUID             0x02
+#define FW_CFG_RAM_SIZE         0x03
+#define FW_CFG_NOGRAPHIC        0x04
+#define FW_CFG_NB_CPUS          0x05
+#define FW_CFG_MACHINE_ID       0x06
+#define FW_CFG_KERNEL_ADDR      0x07
+#define FW_CFG_KERNEL_SIZE      0x08
+#define FW_CFG_KERNEL_CMDLINE   0x09
+#define FW_CFG_INITRD_ADDR      0x0a
+#define FW_CFG_INITRD_SIZE      0x0b
+#define FW_CFG_BOOT_DEVICE      0x0c
+#define FW_CFG_NUMA             0x0d
+#define FW_CFG_BOOT_MENU        0x0e
+#define FW_CFG_MAX_CPUS         0x0f
+#define FW_CFG_KERNEL_ENTRY     0x10
+#define FW_CFG_KERNEL_DATA      0x11
+#define FW_CFG_INITRD_DATA      0x12
+#define FW_CFG_CMDLINE_ADDR     0x13
+#define FW_CFG_CMDLINE_SIZE     0x14
+#define FW_CFG_CMDLINE_DATA     0x15
+#define FW_CFG_SETUP_ADDR       0x16
+#define FW_CFG_SETUP_SIZE       0x17
+#define FW_CFG_SETUP_DATA       0x18
+#define FW_CFG_FILE_DIR         0x19
+
+#define FW_CFG_FILE_FIRST       0x20
+#define FW_CFG_FILE_SLOTS_MIN   0x10
+
+#define FW_CFG_WRITE_CHANNEL    0x4000
+#define FW_CFG_ARCH_LOCAL       0x8000
+#define FW_CFG_ENTRY_MASK       (~(FW_CFG_WRITE_CHANNEL | FW_CFG_ARCH_LOCAL))
+
+#define FW_CFG_INVALID          0xffff
+
+/* width in bytes of fw_cfg control register */
+#define FW_CFG_CTL_SIZE         0x02
+
+/* fw_cfg "file name" is up to 56 characters (including terminating nul) */
+#define FW_CFG_MAX_FILE_PATH    56
+
+/* size in bytes of fw_cfg signature */
+#define FW_CFG_SIG_SIZE 4
+
+/* FW_CFG_ID bits */
+#define FW_CFG_VERSION          0x01
+
+/* fw_cfg file directory entry type */
+struct fw_cfg_file {
+        __be32 size;
+        __be16 select;
+        __u16 reserved;
+        char name[FW_CFG_MAX_FILE_PATH];
+};
+
+#endif