diff options
Diffstat (limited to 'drivers/media/rc/ir-imon-decoder.c')
| -rw-r--r-- | drivers/media/rc/ir-imon-decoder.c | 193 |
1 files changed, 193 insertions, 0 deletions
diff --git a/drivers/media/rc/ir-imon-decoder.c b/drivers/media/rc/ir-imon-decoder.c new file mode 100644 index 000000000000..a1ff06a26542 --- /dev/null +++ b/drivers/media/rc/ir-imon-decoder.c @@ -0,0 +1,193 @@ +// SPDX-License-Identifier: GPL-2.0+ +// ir-imon-decoder.c - handle iMon protocol +// +// Copyright (C) 2018 by Sean Young <sean@mess.org> + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include <linux/module.h> +#include "rc-core-priv.h" + +#define IMON_UNIT 415662 /* ns */ +#define IMON_BITS 30 +#define IMON_CHKBITS (BIT(30) | BIT(25) | BIT(24) | BIT(22) | \ + BIT(21) | BIT(20) | BIT(19) | BIT(18) | \ + BIT(17) | BIT(16) | BIT(14) | BIT(13) | \ + BIT(12) | BIT(11) | BIT(10) | BIT(9)) + +/* + * This protocol has 30 bits. The format is one IMON_UNIT header pulse, + * followed by 30 bits. Each bit is one IMON_UNIT check field, and then + * one IMON_UNIT field with the actual bit (1=space, 0=pulse). + * The check field is always space for some bits, for others it is pulse if + * both the preceding and current bit are zero, else space. IMON_CHKBITS + * defines which bits are of type check. + * + * There is no way to distinguish an incomplete message from one where + * the lower bits are all set, iow. the last pulse is for the lowest + * bit which is 0. + */ +enum imon_state { + STATE_INACTIVE, + STATE_BIT_CHK, + STATE_BIT_START, + STATE_FINISHED +}; + +/** + * ir_imon_decode() - Decode one iMON pulse or space + * @dev: the struct rc_dev descriptor of the device + * @ev: the struct ir_raw_event descriptor of the pulse/space + * + * This function returns -EINVAL if the pulse violates the state machine + */ +static int ir_imon_decode(struct rc_dev *dev, struct ir_raw_event ev) +{ + struct imon_dec *data = &dev->raw->imon; + + if (!is_timing_event(ev)) { + if (ev.reset) + data->state = STATE_INACTIVE; + return 0; + } + + dev_dbg(&dev->dev, + "iMON decode started at state %d bitno %d (%uus %s)\n", + data->state, data->count, TO_US(ev.duration), + TO_STR(ev.pulse)); + + for (;;) { + if (!geq_margin(ev.duration, IMON_UNIT, IMON_UNIT / 2)) + return 0; + + decrease_duration(&ev, IMON_UNIT); + + switch (data->state) { + case STATE_INACTIVE: + if (ev.pulse) { + data->state = STATE_BIT_CHK; + data->bits = 0; + data->count = IMON_BITS; + } + break; + case STATE_BIT_CHK: + if (IMON_CHKBITS & BIT(data->count)) + data->last_chk = ev.pulse; + else if (ev.pulse) + goto err_out; + data->state = STATE_BIT_START; + break; + case STATE_BIT_START: + data->bits <<= 1; + if (!ev.pulse) + data->bits |= 1; + + if (IMON_CHKBITS & BIT(data->count)) { + if (data->last_chk != !(data->bits & 3)) + goto err_out; + } + + if (!data->count--) + data->state = STATE_FINISHED; + else + data->state = STATE_BIT_CHK; + break; + case STATE_FINISHED: + if (ev.pulse) + goto err_out; + rc_keydown(dev, RC_PROTO_IMON, data->bits, 0); + data->state = STATE_INACTIVE; + break; + } + } + +err_out: + dev_dbg(&dev->dev, + "iMON decode failed at state %d bitno %d (%uus %s)\n", + data->state, data->count, TO_US(ev.duration), + TO_STR(ev.pulse)); + + data->state = STATE_INACTIVE; + + return -EINVAL; +} + +/** + * ir_imon_encode() - Encode a scancode as a stream of raw events + * + * @protocol: protocol to encode + * @scancode: scancode to encode + * @events: array of raw ir events to write into + * @max: maximum size of @events + * + * Returns: The number of events written. + * -ENOBUFS if there isn't enough space in the array to fit the + * encoding. In this case all @max events will have been written. + */ +static int ir_imon_encode(enum rc_proto protocol, u32 scancode, + struct ir_raw_event *events, unsigned int max) +{ + struct ir_raw_event *e = events; + int i, pulse; + + if (!max--) + return -ENOBUFS; + init_ir_raw_event_duration(e, 1, IMON_UNIT); + + for (i = IMON_BITS; i >= 0; i--) { + if (BIT(i) & IMON_CHKBITS) + pulse = !(scancode & (BIT(i) | BIT(i + 1))); + else + pulse = 0; + + if (pulse == e->pulse) { + e->duration += IMON_UNIT; + } else { + if (!max--) + return -ENOBUFS; + init_ir_raw_event_duration(++e, pulse, IMON_UNIT); + } + + pulse = !(scancode & BIT(i)); + + if (pulse == e->pulse) { + e->duration += IMON_UNIT; + } else { + if (!max--) + return -ENOBUFS; + init_ir_raw_event_duration(++e, pulse, IMON_UNIT); + } + } + + if (e->pulse) + e++; + + return e - events; +} + +static struct ir_raw_handler imon_handler = { + .protocols = RC_PROTO_BIT_IMON, + .decode = ir_imon_decode, + .encode = ir_imon_encode, + .carrier = 38000, +}; + +static int __init ir_imon_decode_init(void) +{ + ir_raw_handler_register(&imon_handler); + + pr_info("IR iMON protocol handler initialized\n"); + return 0; +} + +static void __exit ir_imon_decode_exit(void) +{ + ir_raw_handler_unregister(&imon_handler); +} + +module_init(ir_imon_decode_init); +module_exit(ir_imon_decode_exit); + +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("Sean Young <sean@mess.org>"); +MODULE_DESCRIPTION("iMON IR protocol decoder"); |