static ssize_t sys_t_write()

in stm/p_sys-t.c [287:356]

• 47 lines of code
• 13 McCabe index (conditional complexity)

static ssize_t sys_t_write(struct stm_data *data, struct stm_output *output,
			   unsigned int chan, const char *buf, size_t count)
{
	struct sys_t_output *op = output->pdrv_private;
	unsigned int c = output->channel + chan;
	unsigned int m = output->master;
	const unsigned char nil = 0;
	u32 header = DATA_HEADER;
	u8 uuid[UUID_SIZE];
	ssize_t sz;

	/* We require an existing policy node to proceed */
	if (!op)
		return -EINVAL;

	if (sys_t_need_clock_sync(op)) {
		sz = sys_t_clock_sync(data, m, c);
		if (sz <= 0)
			return sz;
	}

	if (op->node.do_len)
		header |= MIPI_SYST_OPT_LEN;
	if (sys_t_need_ts(op))
		header |= MIPI_SYST_OPT_TS;

	/*
	 * STP framing rules for SyS-T frames:
	 *   * the first packet of the SyS-T frame is timestamped;
	 *   * the last packet is a FLAG.
	 */
	/* Message layout: HEADER / GUID / [LENGTH /][TIMESTAMP /] DATA */
	/* HEADER */
	sz = data->packet(data, m, c, STP_PACKET_DATA, STP_PACKET_TIMESTAMPED,
			  4, (u8 *)&header);
	if (sz <= 0)
		return sz;

	/* GUID */
	export_uuid(uuid, &op->node.uuid);
	sz = stm_data_write(data, m, c, false, uuid, sizeof(op->node.uuid));
	if (sz <= 0)
		return sz;

	/* [LENGTH] */
	if (op->node.do_len) {
		u16 length = count;

		sz = data->packet(data, m, c, STP_PACKET_DATA, 0, 2,
				  (u8 *)&length);
		if (sz <= 0)
			return sz;
	}

	/* [TIMESTAMP] */
	if (header & MIPI_SYST_OPT_TS) {
		u64 ts = ktime_get_real_ns();

		sz = stm_data_write(data, m, c, false, &ts, sizeof(ts));
		if (sz <= 0)
			return sz;
	}

	/* DATA */
	sz = stm_data_write(data, m, c, false, buf, count);
	if (sz > 0)
		data->packet(data, m, c, STP_PACKET_FLAG, 0, 0, &nil);

	return sz;
}