[PATCH 1/4] include/uapi/linux: add gxfp_ioctl.h for GXFP5130 fingerprint sensor

["Metehan Günen" <metehangnen@gmail.com>]

Define the userspace ABI for the Goodix GXFP5130 eSPI fingerprint sensor
driver:

 - struct gxfp_tap_hdr: header prepended to every read(2) record, carries
   payload length, MP protocol type and a ktime_get_ns() timestamp.
 - struct gxfp_tx_pkt_hdr: header that userspace prepends to write(2)
   payloads so the driver can wrap them in the eSPI frame format.
 - GXFP_IOCTL_FLUSH_RXQ: flush the kernel-side RX record queue.

Signed-off-by: Metehan Günen <metehangnen@gmail.com>
---
 include/uapi/linux/gxfp_ioctl.h | 43 +++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)
 create mode 100644 include/uapi/linux/gxfp_ioctl.h

diff --git a/include/uapi/linux/gxfp_ioctl.h b/include/uapi/linux/gxfp_ioctl.h
new file mode 100644
index 000000000..c9c6c2d48
--- /dev/null
+++ b/include/uapi/linux/gxfp_ioctl.h
@@ -0,0 +1,43 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __UAPI_GXFP_IOCTL_H
+#define __UAPI_GXFP_IOCTL_H
+
+#include <linux/types.h>
+#include <linux/ioctl.h>
+
+#define GXFP_IOCTL_MAGIC 'G'
+
+/*
+ * 4-byte MP header + payload must fit GXFP_TX_BUFFER_SIZE(512).
+ */
+#define GXFP_IOCTL_TX_PAYLOAD_MAX 508u
+
+/* Maximum protocol payload bytes exported via read(2) records. */
+#define GXFP_IOCTL_TAP_PAYLOAD_MAX (128u * 1024u)
+
+/*
+ * Stream tap (read/poll) record header.
+ * Followed by `len` bytes of protocol payload.
+ */
+struct gxfp_tap_hdr {
+	__u32 len;       /* protocol payload bytes */
+	__u32 type;      /* MP type */
+	__u32 _rsvd0;
+	__u64 ts_ns;     /* ktime_get_ns() */
+	__u8 head16[16]; /* first 16 bytes of payload */
+};
+
+/*
+ * write(2) packet header.
+ * Userspace writes: [gxfp_tx_pkt_hdr][payload bytes]
+ */
+struct gxfp_tx_pkt_hdr {
+	__u8 mp_flags;
+	__u8 _pad0;
+	__u16 payload_len;
+	__u32 flags;
+};
+
+#define GXFP_IOCTL_FLUSH_RXQ _IO(GXFP_IOCTL_MAGIC, 0x11)
+
+#endif /* __UAPI_GXFP_IOCTL_H */
-- 
2.55.0