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Diffstat (limited to 'include/uapi/sound/fcp.h')
| -rw-r--r-- | include/uapi/sound/fcp.h | 120 |
1 files changed, 120 insertions, 0 deletions
diff --git a/include/uapi/sound/fcp.h b/include/uapi/sound/fcp.h new file mode 100644 index 000000000000..aea428956d8f --- /dev/null +++ b/include/uapi/sound/fcp.h @@ -0,0 +1,120 @@ +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */ +/* + * Focusrite Control Protocol Driver for ALSA + * + * Copyright (c) 2024-2025 by Geoffrey D. Bennett <g at b4.vu> + */ +/* + * DOC: FCP (Focusrite Control Protocol) User-Space API + * + * This header defines the interface between the FCP kernel driver and + * user-space programs to enable the use of the proprietary features + * available in Focusrite USB audio interfaces. This includes Scarlett + * 2nd Gen, 3rd Gen, 4th Gen, Clarett USB, Clarett+, and Vocaster + * series devices. + * + * The interface is provided via ALSA's hwdep interface. Opening the + * hwdep device requires CAP_SYS_RAWIO privileges as this interface + * provides near-direct access. + * + * For details on the FCP protocol, refer to the kernel scarlett2 + * driver in sound/usb/mixer_scarlett2.c and the fcp-support project + * at https://github.com/geoffreybennett/fcp-support + * + * For examples of using these IOCTLs, see the fcp-server source in + * the fcp-support project. + * + * IOCTL Interface + * -------------- + * FCP_IOCTL_PVERSION: + * Returns the protocol version supported by the driver. + * + * FCP_IOCTL_INIT: + * Initialises the protocol and synchronises sequence numbers + * between the driver and device. Must be called at least once + * before sending commands. Can be safely called again at any time. + * + * FCP_IOCTL_CMD: + * Sends an FCP command to the device and returns the response. + * Requires prior initialisation via FCP_IOCTL_INIT. + * + * FCP_IOCTL_SET_METER_MAP: + * Configures the Level Meter control's mapping between device + * meters and control channels. Requires FCP_IOCTL_INIT to have been + * called first. The map size and number of slots cannot be changed + * after initial configuration, although the map itself can be + * updated. Once configured, the Level Meter remains functional even + * after the hwdep device is closed. + * + * FCP_IOCTL_SET_METER_LABELS: + * Set the labels for the Level Meter control. Requires + * FCP_IOCTL_SET_METER_MAP to have been called first. labels[] + * should contain a sequence of null-terminated labels corresponding + * to the control's channels. + */ +#ifndef __UAPI_SOUND_FCP_H +#define __UAPI_SOUND_FCP_H + +#include <linux/types.h> +#include <linux/ioctl.h> + +#define FCP_HWDEP_MAJOR 2 +#define FCP_HWDEP_MINOR 0 +#define FCP_HWDEP_SUBMINOR 0 + +#define FCP_HWDEP_VERSION \ + ((FCP_HWDEP_MAJOR << 16) | \ + (FCP_HWDEP_MINOR << 8) | \ + FCP_HWDEP_SUBMINOR) + +#define FCP_HWDEP_VERSION_MAJOR(v) (((v) >> 16) & 0xFF) +#define FCP_HWDEP_VERSION_MINOR(v) (((v) >> 8) & 0xFF) +#define FCP_HWDEP_VERSION_SUBMINOR(v) ((v) & 0xFF) + +/* Get protocol version */ +#define FCP_IOCTL_PVERSION _IOR('S', 0x60, int) + +/* Start the protocol */ + +/* Step 0 and step 2 responses are variable length and placed in + * resp[] one after the other. + */ +struct fcp_init { + __u16 step0_resp_size; + __u16 step2_resp_size; + __u32 init1_opcode; + __u32 init2_opcode; + __u8 resp[]; +} __attribute__((packed)); + +#define FCP_IOCTL_INIT _IOWR('S', 0x64, struct fcp_init) + +/* Perform a command */ + +/* The request data is placed in data[] and the response data will + * overwrite it. + */ +struct fcp_cmd { + __u32 opcode; + __u16 req_size; + __u16 resp_size; + __u8 data[]; +} __attribute__((packed)); +#define FCP_IOCTL_CMD _IOWR('S', 0x65, struct fcp_cmd) + +/* Set the meter map */ +struct fcp_meter_map { + __u16 map_size; + __u16 meter_slots; + __s16 map[]; +} __attribute__((packed)); +#define FCP_IOCTL_SET_METER_MAP _IOW('S', 0x66, struct fcp_meter_map) + +/* Set the meter labels */ +struct fcp_meter_labels { + __u16 labels_size; + char labels[]; +} __attribute__((packed)); +#define FCP_IOCTL_SET_METER_LABELS _IOW('S', 0x67, struct fcp_meter_labels) + +#endif /* __UAPI_SOUND_FCP_H */ |