On 19 October 2016 at 00:29, Steven Rostedt <rost...@goodmis.org> wrote: > On Tue, 18 Oct 2016 16:08:59 +0800 > Chunyan Zhang <zhang.chun...@linaro.org> wrote: > >> This patch adds a driver that models itself as an stm_source called >> stm_ftrace. Once the stm device and stm_ftrace have been linked via >> sysfs, the driver registers itself as a trace_export and everything >> passed to the interface from Ftrace subsystem will end up in the STM >> trace engine. >> >> Signed-off-by: Chunyan Zhang <zhang.chun...@linaro.org> >> --- >> drivers/hwtracing/stm/Kconfig | 11 ++++++ >> drivers/hwtracing/stm/Makefile | 2 + >> drivers/hwtracing/stm/ftrace.c | 88 >> ++++++++++++++++++++++++++++++++++++++++++ >> 3 files changed, 101 insertions(+) >> create mode 100644 drivers/hwtracing/stm/ftrace.c >> >> diff --git a/drivers/hwtracing/stm/Kconfig b/drivers/hwtracing/stm/Kconfig >> index 847a39b..b34ea96 100644 >> --- a/drivers/hwtracing/stm/Kconfig >> +++ b/drivers/hwtracing/stm/Kconfig >> @@ -39,4 +39,15 @@ config STM_SOURCE_HEARTBEAT >> If you want to send heartbeat messages over STM devices, >> say Y. >> >> +config STM_SOURCE_FTRACE >> + tristate "Copy the output from kernel Ftrace to STM engine" >> + depends on TRACING > > I think it should depend on FUNCTION_TRACER
I think we should support other type of tracer in the future, but you're right it only should depend on FUNCTION_TRACER for now, I will revise this. > >> + help >> + This option can be used to copy the output from kernel Ftrace >> + to STM engine. Enabling this option will introduce a slight >> + timing effect. >> + >> + If you want to send kernel Ftrace messages over STM devices, >> + say Y. >> + >> endif >> diff --git a/drivers/hwtracing/stm/Makefile b/drivers/hwtracing/stm/Makefile >> index a9ce3d4..3abd84c 100644 >> --- a/drivers/hwtracing/stm/Makefile >> +++ b/drivers/hwtracing/stm/Makefile >> @@ -6,6 +6,8 @@ obj-$(CONFIG_STM_DUMMY) += dummy_stm.o >> >> obj-$(CONFIG_STM_SOURCE_CONSOLE) += stm_console.o >> obj-$(CONFIG_STM_SOURCE_HEARTBEAT) += stm_heartbeat.o >> +obj-$(CONFIG_STM_SOURCE_FTRACE) += stm_ftrace.o >> >> stm_console-y := console.o >> stm_heartbeat-y := heartbeat.o >> +stm_ftrace-y := ftrace.o >> diff --git a/drivers/hwtracing/stm/ftrace.c b/drivers/hwtracing/stm/ftrace.c >> new file mode 100644 >> index 0000000..1a114c8f >> --- /dev/null >> +++ b/drivers/hwtracing/stm/ftrace.c >> @@ -0,0 +1,88 @@ >> +/* >> + * Simple kernel driver to link kernel Ftrace and an STM device >> + * Copyright (c) 2016, Linaro Ltd. >> + * >> + * This program is free software; you can redistribute it and/or modify it >> + * under the terms and conditions of the GNU General Public License, >> + * version 2, as published by the Free Software Foundation. >> + * >> + * This program is distributed in the hope it will be useful, but WITHOUT >> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or >> + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for >> + * more details. >> + * >> + * STM Ftrace will be registered as a trace_export. >> + */ >> + >> +#include <linux/module.h> >> +#include <linux/stm.h> >> +#include <linux/trace.h> >> + >> +#define STM_FTRACE_NR_CHANNELS 1 >> +#define STM_FTRACE_CHAN 0 >> + >> +static int stm_ftrace_link(struct stm_source_data *data); >> +static void stm_ftrace_unlink(struct stm_source_data *data); >> + >> +static struct stm_ftrace { >> + struct stm_source_data data; >> + struct trace_export ftrace; >> +} stm_ftrace = { >> + .data = { >> + .name = "ftrace", >> + .nr_chans = STM_FTRACE_NR_CHANNELS, >> + .link = stm_ftrace_link, >> + .unlink = stm_ftrace_unlink, >> + }, >> +}; >> + >> +/** >> + * stm_ftrace_write() - write data to STM via 'stm_ftrace' source >> + * @buf: buffer containing the data packet >> + * @len: length of the data packet >> + */ >> +static void notrace >> +stm_ftrace_write(const char *buf, unsigned int len) >> +{ >> + stm_source_write(&stm_ftrace.data, STM_FTRACE_CHAN, buf, len); >> +} >> + >> +static int stm_ftrace_link(struct stm_source_data *data) >> +{ >> + struct stm_ftrace *sf = container_of(data, struct stm_ftrace, data); >> + >> + sf->ftrace.write = stm_ftrace_write; >> + sf->ftrace.next = NULL; > > Why setting this to NULL? register_ftrace_export() should not require > nor depend on that. Right, it's not required indeed, will remove it. Thanks, Chunyan > > -- Steve > >> + >> + return register_ftrace_export(&sf->ftrace); >> +} >> + >> +static void stm_ftrace_unlink(struct stm_source_data *data) >> +{ >> + struct stm_ftrace *sf = container_of(data, struct stm_ftrace, data); >> + >> + unregister_ftrace_export(&sf->ftrace); >> +} >> + >> +static int __init stm_ftrace_init(void) >> +{ >> + int ret; >> + >> + ret = stm_source_register_device(NULL, &stm_ftrace.data); >> + if (ret) >> + pr_err("Failed to register stm_source - ftrace.\n"); >> + >> + return ret; >> +} >> + >> +static void __exit stm_ftrace_exit(void) >> +{ >> + stm_source_unregister_device(&stm_ftrace.data); >> +} >> + >> +module_init(stm_ftrace_init); >> +module_exit(stm_ftrace_exit); >> + >> +MODULE_LICENSE("GPL v2"); >> +MODULE_DESCRIPTION("stm_ftrace driver"); >> +MODULE_AUTHOR("Chunyan Zhang <zhang.chun...@linaro.org>"); >