// SPDX-License-Identifier: GPL-2.0-or-later/* * A udbg backend which logs messages and reads input from in memory * buffers. * * The console output can be read from memcons_output which is a * circular buffer whose next write position is stored in memcons.output_pos. * * Input may be passed by writing into the memcons_input buffer when it is * empty. The input buffer is empty when both input_pos == input_start and * *input_start == '\0'. * * Copyright (C) 2003-2005 Anton Blanchard and Milton Miller, IBM Corp * Copyright (C) 2013 Alistair Popple, IBM Corp */ #include <linux/kernel.h>#include <asm/barrier.h>#include <asm/page.h>#include <asm/processor.h>#include <asm/udbg.h> struct memcons {	char *output_start;	char *output_pos;	char *output_end;	char *input_start;	char *input_pos;	char *input_end;}; static char memcons_output[CONFIG_PPC_MEMCONS_OUTPUT_SIZE];static char memcons_input[CONFIG_PPC_MEMCONS_INPUT_SIZE]; struct memcons memcons = {	.output_start = memcons_output,	.output_pos = memcons_output,	.output_end = &memcons_output[CONFIG_PPC_MEMCONS_OUTPUT_SIZE],	.input_start = memcons_input,	.input_pos = memcons_input,	.input_end = &memcons_input[CONFIG_PPC_MEMCONS_INPUT_SIZE],}; static void memcons_putc(char c){	char *new_output_pos; 	*memcons.output_pos = c;	wmb();	new_output_pos = memcons.output_pos + 1;	if (new_output_pos >= memcons.output_end)		new_output_pos = memcons.output_start; 	memcons.output_pos = new_output_pos;} static int memcons_getc_poll(void){	char c;	char *new_input_pos; 	if (*memcons.input_pos) {		c = *memcons.input_pos; 		new_input_pos = memcons.input_pos + 1;		if (new_input_pos >= memcons.input_end)			new_input_pos = memcons.input_start;		else if (*new_input_pos == '\0')			new_input_pos = memcons.input_start; 		*memcons.input_pos = '\0';		wmb();		memcons.input_pos = new_input_pos;		return c;	} 	return -1;} static int memcons_getc(void){	int c; 	while (1) {		c = memcons_getc_poll();		if (c == -1)			cpu_relax();		else			break;	} 	return c;} void __init udbg_init_memcons(void){	udbg_putc = memcons_putc;	udbg_getc = memcons_getc;	udbg_getc_poll = memcons_getc_poll;}