[PATCH V3 2/3] stm class: ftrace: Add ftrace-export-over-stm driver

[Chunyan Zhang]

Removing maxime.coquelin at st.com since it seems an unreachable address

On Tue, Aug 9, 2016 at 2:32 PM, Chunyan Zhang <zhang.chunyan at linaro.org> wrote:
> This patch adds a driver that models itself as an stm_source and
> registers itself as a trace_export.  Once the stm and stm_source
> have been linked via sysfs, everything that is passed to the
> interface from Ftrace subsystem will endup in the STM trace engine.
>
> Signed-off-by: Chunyan Zhang <zhang.chunyan at linaro.org>
> ---
>  drivers/hwtracing/stm/Kconfig  | 11 ++++++
>  drivers/hwtracing/stm/Makefile |  2 +
>  drivers/hwtracing/stm/ftrace.c | 87 ++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 100 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
> +       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..1101f46
> --- /dev/null
> +++ b/drivers/hwtracing/stm/ftrace.c
> @@ -0,0 +1,87 @@
> +/*
> + * 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.
> + */
> +
> +#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);
> +
> +       strcpy(sf->ftrace.name, "stm_ftrace");
> +       sf->ftrace.write = stm_ftrace_write;
> +       sf->ftrace.next = NULL;
> +
> +       return register_trace_export(&sf->ftrace);
> +}
> +
> +static void stm_ftrace_unlink(struct stm_source_data *data)
> +{
> +       struct stm_ftrace *sc = container_of(data, struct stm_ftrace, data);
> +
> +       unregister_trace_export(&sc->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.chunyan at linaro.org>");
> --
> 2.7.4
>