[PATCH v3 1/2] remoteproc: Add a sysfs interface for firmware and state

[Matt Redfearn <matt.redfearn@imgtec.com>]

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@imgtec.com>

---

Changes in v3:
Drop call to rproc_add_virtio_devices from sysfs firmware_store
Use strcspn to find firmware name length
Explicit indexes for state strings

Changes in v2:
Have firmware_store perform the necessary steps inline.
Use sysfs_streq when dealing with writes to sysfs files

 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            | 151 +++++++++++++++++++++++
 5 files changed, 210 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@imgtec.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@imgtec.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 6dfb62ed643f..6da9b12f9798 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 ccc2a73e94dd..b1860949d106 100644
--- a/drivers/remoteproc/remoteproc_core.c
+++ b/drivers/remoteproc/remoteproc_core.c
@@ -1347,6 +1347,7 @@ 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);
@@ -1485,6 +1486,7 @@ EXPORT_SYMBOL(rproc_report_crash);
 
 static int __init remoteproc_init(void)
 {
+	rproc_init_sysfs();
 	rproc_init_debugfs();
 
 	return 0;
@@ -1496,6 +1498,7 @@ 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 4cf93ca2816e..c2c3e4762b90 100644
--- a/drivers/remoteproc/remoteproc_internal.h
+++ b/drivers/remoteproc/remoteproc_internal.h
@@ -63,6 +63,11 @@ 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..bc5b0e00efb1
--- /dev/null
+++ b/drivers/remoteproc/remoteproc_sysfs.c
@@ -0,0 +1,151 @@
+/*
+ * 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);
+
+	return sprintf(buf, "%s\n", rproc->firmware);
+}
+
+/* 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);
+	char *p;
+	int err, len = count;
+
+	err = mutex_lock_interruptible(&rproc->lock);
+	if (err) {
+		dev_err(dev, "can't lock rproc %s: %d\n", rproc->name, err);
+		return -EINVAL;
+	}
+
+	if (rproc->state != RPROC_OFFLINE) {
+		dev_err(dev, "can't change firmware while running\n");
+		err = -EBUSY;
+		goto out;
+	}
+
+	len = strcspn(buf, "\n");
+
+	p = kstrndup(buf, len, GFP_KERNEL);
+	if (!p) {
+		err = -ENOMEM;
+		goto out;
+	}
+
+	kfree(rproc->firmware);
+	rproc->firmware = p;
+out:
+	mutex_unlock(&rproc->lock);
+
+	return err ? err : count;
+}
+static DEVICE_ATTR_RW(firmware);
+
+/*
+ * 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[] = {
+	[RPROC_OFFLINE]		= "offline",
+	[RPROC_SUSPENDED]	= "suspended",
+	[RPROC_RUNNING]		= "running",
+	[RPROC_CRASHED]		= "crashed",
+	[RPROC_LAST]		= "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 sprintf(buf, "%s\n", rproc_state_string[state]);
+}
+
+/* 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;
+
+	if (sysfs_streq(buf, "start")) {
+		if (rproc->state == RPROC_RUNNING)
+			return -EBUSY;
+
+		ret = rproc_boot(rproc);
+		if (ret)
+			dev_err(&rproc->dev, "Boot failed: %d\n", ret);
+	} else if (sysfs_streq(buf, "stop")) {
+		if (rproc->state != RPROC_RUNNING)
+			return -EINVAL;
+
+		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 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);
+}
-- 
2.7.4