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
> + 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.
-- 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>");
