Date:   Thu, 13 Oct 2016 22:02:58 -0700
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Matt Redfearn <matt.redfearn@...tec.com>
Cc:     Ohad Ben-Cohen <ohad@...ery.com>, linux-remoteproc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/4] remoteproc: Add a sysfs interface for firmware and
 state

On Tue 11 Oct 06:39 PDT 2016, Matt Redfearn wrote:

> This patch adds a sysfs interface to rproc allowing the firmware name
> and processor state to be changed dynamically.
> 
> State was previously available in debugfs, and is replicated here. The
> firmware file allows retrieval of the running firmware name, and a new
> one to be specified at run time, so long as the remote processor has
> been stopped.
> 
> Signed-off-by: Matt Redfearn <matt.redfearn@...tec.com>
> 
> ---
> 
>  Documentation/ABI/testing/sysfs-class-remoteproc |  50 +++++++++
>  drivers/remoteproc/Makefile                      |   1 +
>  drivers/remoteproc/remoteproc_core.c             |   3 +
>  drivers/remoteproc/remoteproc_internal.h         |   5 +
>  drivers/remoteproc/remoteproc_sysfs.c            | 132 +++++++++++++++++++++++
>  5 files changed, 191 insertions(+)
>  create mode 100644 Documentation/ABI/testing/sysfs-class-remoteproc
>  create mode 100644 drivers/remoteproc/remoteproc_sysfs.c
> 
> diff --git a/Documentation/ABI/testing/sysfs-class-remoteproc b/Documentation/ABI/testing/sysfs-class-remoteproc
> new file mode 100644
> index 000000000000..d188afebc8ba
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-class-remoteproc
> @@ -0,0 +1,50 @@
> +What:		/sys/class/remoteproc/.../firmware
> +Date:		October 2016
> +Contact:	Matt Redfearn <matt.redfearn@...tec.com>
> +Description:	Remote processor firmware
> +
> +		Reports the name of the firmware currently loaded to the
> +		remote processor.
> +
> +		To change the running firmware, ensure the remote processor is
> +		stopped (using /sys/class/remoteproc/.../state) and write a new filename.
> +
> +What:		/sys/class/remoteproc/.../state
> +Date:		October 2016
> +Contact:	Matt Redfearn <matt.redfearn@...tec.com>
> +Description:	Remote processor state
> +
> +		Reports the state of the remote processor, which will be one of:
> +
> +		"offline"
> +		"suspended"
> +		"running"
> +		"crashed"
> +		"invalid"
> +
> +		"offline" means the remote processor is powered off.
> +
> +		"suspended" means that the remote processor is suspended and
> +		must be woken to receive messages.
> +
> +		"running" is the normal state of an available remote processor
> +
> +		"crashed" indicates that a problem/crash has been detected on
> +		the remote processor.
> +
> +		"invalid" is returned if the remote processor is in an
> +		unknown state.
> +
> +		Writing this file controls the state of the remote processor.
> +		The following states can be written:
> +
> +		"start"
> +		"stop"
> +
> +		Writing "start" will attempt to start the processor running the
> +		firmware indicated by, or written to,
> +		/sys/class/remoteproc/.../firmware. The remote processor should
> +		transition to "running" state.
> +
> +		Writing "stop" will attempt to halt the remote processor and
> +		return it to the "offline" state.
> diff --git a/drivers/remoteproc/Makefile b/drivers/remoteproc/Makefile
> index 92d3758bd15c..666258bd80aa 100644
> --- a/drivers/remoteproc/Makefile
> +++ b/drivers/remoteproc/Makefile
> @@ -5,6 +5,7 @@
>  obj-$(CONFIG_REMOTEPROC)		+= remoteproc.o
>  remoteproc-y				:= remoteproc_core.o
>  remoteproc-y				+= remoteproc_debugfs.o
> +remoteproc-y				+= remoteproc_sysfs.o
>  remoteproc-y				+= remoteproc_virtio.o
>  remoteproc-y				+= remoteproc_elf_loader.o
>  obj-$(CONFIG_OMAP_REMOTEPROC)		+= omap_remoteproc.o
> diff --git a/drivers/remoteproc/remoteproc_core.c b/drivers/remoteproc/remoteproc_core.c
> index 2152b484f314..642c5b58fec5 100644
> --- a/drivers/remoteproc/remoteproc_core.c
> +++ b/drivers/remoteproc/remoteproc_core.c
> @@ -1455,6 +1455,7 @@ struct rproc *rproc_alloc(struct device *dev, const char *name,
>  	device_initialize(&rproc->dev);
>  	rproc->dev.parent = dev;
>  	rproc->dev.type = &rproc_type;
> +	rproc->dev.class = &rproc_class;
>  
>  	/* Assign a unique device index and name */
>  	rproc->index = ida_simple_get(&rproc_dev_index, 0, 0, GFP_KERNEL);
> @@ -1580,6 +1581,7 @@ EXPORT_SYMBOL(rproc_report_crash);
>  
>  static int __init remoteproc_init(void)
>  {
> +	rproc_init_sysfs();
>  	rproc_init_debugfs();
>  
>  	return 0;
> @@ -1591,6 +1593,7 @@ static void __exit remoteproc_exit(void)
>  	ida_destroy(&rproc_dev_index);
>  
>  	rproc_exit_debugfs();
> +	rproc_exit_sysfs();
>  }
>  module_exit(remoteproc_exit);
>  
> diff --git a/drivers/remoteproc/remoteproc_internal.h b/drivers/remoteproc/remoteproc_internal.h
> index 837faf2677a6..2beb86ddfacc 100644
> --- a/drivers/remoteproc/remoteproc_internal.h
> +++ b/drivers/remoteproc/remoteproc_internal.h
> @@ -64,6 +64,11 @@ void rproc_create_debug_dir(struct rproc *rproc);
>  void rproc_init_debugfs(void);
>  void rproc_exit_debugfs(void);
>  
> +/* from remoteproc_sysfs.c */
> +extern struct class rproc_class;
> +int rproc_init_sysfs(void);
> +void rproc_exit_sysfs(void);
> +
>  void rproc_free_vring(struct rproc_vring *rvring);
>  int rproc_alloc_vring(struct rproc_vdev *rvdev, int i);
>  
> diff --git a/drivers/remoteproc/remoteproc_sysfs.c b/drivers/remoteproc/remoteproc_sysfs.c
> new file mode 100644
> index 000000000000..892599863ca6
> --- /dev/null
> +++ b/drivers/remoteproc/remoteproc_sysfs.c
> @@ -0,0 +1,132 @@
> +/*
> + * Remote Processor Framework
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License
> + * version 2 as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that 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/remoteproc.h>
> +
> +#include "remoteproc_internal.h"
> +
> +#define to_rproc(d) container_of(d, struct rproc, dev)
> +
> +/* Expose the loaded / running firmware name via sysfs */
> +static ssize_t firmware_show(struct device *dev, struct device_attribute *attr,
> +			  char *buf)
> +{
> +	struct rproc *rproc = to_rproc(dev);
> +
> +	if (rproc->firmware)
> +		return sprintf(buf, "%s\n", rproc->firmware);
> +	else
> +		return sprintf(buf, "unknown");

Per current and future logic, rproc->firmware can't be NULL.

> +}
> +
> +/* Change firmware name via sysfs */
> +static ssize_t firmware_store(struct device *dev,
> +			      struct device_attribute *attr,
> +			      const char *buf, size_t count)
> +{
> +	struct rproc *rproc = to_rproc(dev);
> +	int err;
> +
> +	err = rproc_change_firmware(rproc, buf);

Rather than introducing rproc_set_firmware_name() and
rproc_change_firmware() - which does not have a use case beyond this
caller you should be able to keep rproc_alloc() more or less as is, and
then inline a simplified version (as we don't have to deal with the
templated case here).

> +	return err ? err : count;
> +}
> +static DEVICE_ATTR_RW(firmware);
> +

Extra newline...

> +
> +/*
> + * A state-to-string lookup table, for exposing a human readable state
> + * via sysfs. Always keep in sync with enum rproc_state
> + */
> +static const char * const rproc_state_string[] = {
> +	"offline",
> +	"suspended",
> +	"running",
> +	"crashed",
> +	"invalid",
> +};
> +
> +/* Expose the state of the remote processor via sysfs */
> +static ssize_t state_show(struct device *dev, struct device_attribute *attr,
> +			  char *buf)
> +{
> +	struct rproc *rproc = to_rproc(dev);
> +	unsigned int state;
> +
> +	state = rproc->state > RPROC_LAST ? RPROC_LAST : rproc->state;
> +	return scnprintf(buf, 30, "%.28s (%d)\n",
> +			 rproc_state_string[state], rproc->state);

The documentation above does not describe the "($state)" part, which I'm
fine leaving out. We know the strings are below PAGE_SIZE, so you can
use sprintf().

> +}
> +
> +/* Change remote processor state via sysfs */
> +static ssize_t state_store(struct device *dev,
> +			      struct device_attribute *attr,
> +			      const char *buf, size_t count)
> +{
> +	struct rproc *rproc = to_rproc(dev);
> +	int ret = 0;
> +	int len = count;
> +
> +	if (buf[len - 1] == '\n')
> +		len--;
> +
> +	if (!strncmp(buf, "start", len)) {

Please use sysfs_streq() instead, it will handle the \n for you.

> +		if (rproc->state == RPROC_RUNNING)
> +			return -EBUSY;
> +
> +		ret = rproc_boot(rproc);
> +		if (ret)
> +			dev_err(&rproc->dev, "Boot failed: %d\n", ret);
> +	} else if (!strncmp(buf, "stop", len)) {
> +		rproc_shutdown(rproc);
> +	} else {
> +		dev_err(&rproc->dev, "Unrecognised option: %s\n", buf);
> +		ret = -EINVAL;
> +	}
> +	return ret ? ret : count;
> +}
> +static DEVICE_ATTR_RW(state);
> +
> +static const struct attribute *rproc_attrs[] = {
> +	&dev_attr_firmware.attr,
> +	&dev_attr_state.attr,
> +	NULL
> +};
> +
> +static const struct attribute_group rproc_devgroup = {
> +	.attrs = rproc_attrs
> +};
> +
> +static const struct attribute_group *rproc_devgroups[] = {
> +	&rproc_devgroup,
> +	NULL
> +};
> +
> +struct class rproc_class = {
> +	.name		= "remoteproc",
> +	.dev_groups	= rproc_devgroups,
> +};
> +
> +int __init rproc_init_sysfs(void)
> +{
> +	/* create remoteproc device class for sysfs */
> +	int err = class_register(&rproc_class);
> +
> +	if (err)
> +		pr_err("remoteproc: unable to register class\n");
> +	return err;
> +}
> +
> +void __exit rproc_exit_sysfs(void)
> +{
> +	class_unregister(&rproc_class);
> +}

Besides these nits, I think this looks good.

Thanks,
Bjorn

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