[RFC 1/2] devlink: add simple fw crash helpers

[Jakub Kicinski <kuba@kernel.org>]

Add infra for creating devlink instances for a device to report
fw crashes. This patch expects the devlink instance to be registered
at probe time. I belive to be the cleanest. We can also add a devm
version of the helpers, so that we don't have to do the clean up.
Or we can go even further and register the devlink instance only
once error has happened (for the first time, then we can just
find out if already registered by traversing the list like we
do here).

With the patch applied and a sample driver converted we get:

$ devlink dev
pci/0000:07:00.0

Then monitor for errors:

$ devlink mon health
[health,status] pci/0000:07:00.0:
  reporter fw
    state error error 1 recover 0
[health,status] pci/0000:07:00.0:
  reporter fw
    state error error 2 recover 0

These are the events I triggered on purpose. One can also inspect
the health of all devices capable of reporting fw errors:

$ devlink health
pci/0000:07:00.0:
  reporter fw
    state error error 7 recover 0

Obviously drivers may upgrade to the full devlink health API
which includes state dump, state dump auto-collect and automatic
error recovery control.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
 include/linux/devlink.h               |  11 +++
 net/core/Makefile                     |   2 +-
 net/core/devlink_simple_fw_reporter.c | 101 ++++++++++++++++++++++++++
 3 files changed, 113 insertions(+), 1 deletion(-)
 create mode 100644 include/linux/devlink.h
 create mode 100644 net/core/devlink_simple_fw_reporter.c

diff --git a/include/linux/devlink.h b/include/linux/devlink.h
new file mode 100644
index 000000000000..2b73987eefca
--- /dev/null
+++ b/include/linux/devlink.h
@@ -0,0 +1,11 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+#ifndef _LINUX_DEVLINK_H_
+#define _LINUX_DEVLINK_H_
+
+struct device;
+
+void devlink_simple_fw_reporter_prepare(struct device *dev);
+void devlink_simple_fw_reporter_cleanup(struct device *dev);
+void devlink_simple_fw_reporter_report_crash(struct device *dev);
+
+#endif
diff --git a/net/core/Makefile b/net/core/Makefile
index 3e2c378e5f31..6f1513781c17 100644
--- a/net/core/Makefile
+++ b/net/core/Makefile
@@ -31,7 +31,7 @@ obj-$(CONFIG_LWTUNNEL_BPF) += lwt_bpf.o
 obj-$(CONFIG_BPF_STREAM_PARSER) += sock_map.o
 obj-$(CONFIG_DST_CACHE) += dst_cache.o
 obj-$(CONFIG_HWBM) += hwbm.o
-obj-$(CONFIG_NET_DEVLINK) += devlink.o
+obj-$(CONFIG_NET_DEVLINK) += devlink.o devlink_simple_fw_reporter.o
 obj-$(CONFIG_GRO_CELLS) += gro_cells.o
 obj-$(CONFIG_FAILOVER) += failover.o
 obj-$(CONFIG_BPF_SYSCALL) += bpf_sk_storage.o
diff --git a/net/core/devlink_simple_fw_reporter.c b/net/core/devlink_simple_fw_reporter.c
new file mode 100644
index 000000000000..48dde9123c3c
--- /dev/null
+++ b/net/core/devlink_simple_fw_reporter.c
@@ -0,0 +1,101 @@
+#include <linux/devlink.h>
+#include <linux/list.h>
+#include <linux/mutex.h>
+#include <net/devlink.h>
+
+struct devlink_simple_fw_reporter {
+	struct list_head list;
+	struct devlink_health_reporter *reporter;
+};
+
+
+static LIST_HEAD(devlink_simple_fw_reporters);
+static DEFINE_MUTEX(devlink_simple_fw_reporters_mutex);
+
+static const struct devlink_health_reporter_ops simple_devlink_health = {
+	.name = "fw",
+};
+
+static const struct devlink_ops simple_devlink_ops = {
+};
+
+static struct devlink_simple_fw_reporter *
+devlink_simple_fw_reporter_find_for_dev(struct device *dev)
+{
+	struct devlink_simple_fw_reporter *simple_devlink, *ret = NULL;
+	struct devlink *devlink;
+
+	mutex_lock(&devlink_simple_fw_reporters_mutex);
+	list_for_each_entry(simple_devlink, &devlink_simple_fw_reporters,
+			    list) {
+		devlink = priv_to_devlink(simple_devlink);
+		if (devlink->dev == dev) {
+			ret = simple_devlink;
+			break;
+		}
+	}
+	mutex_unlock(&devlink_simple_fw_reporters_mutex);
+
+	return ret;
+}
+
+void devlink_simple_fw_reporter_report_crash(struct device *dev)
+{
+	struct devlink_simple_fw_reporter *simple_devlink;
+
+	simple_devlink = devlink_simple_fw_reporter_find_for_dev(dev);
+	if (!simple_devlink)
+		return;
+
+	devlink_health_report(simple_devlink->reporter, "firmware crash", NULL);
+}
+EXPORT_SYMBOL_GPL(devlink_simple_fw_reporter_report_crash);
+
+void devlink_simple_fw_reporter_prepare(struct device *dev)
+{
+	struct devlink_simple_fw_reporter *simple_devlink;
+	struct devlink *devlink;
+
+	devlink = devlink_alloc(&simple_devlink_ops,
+				sizeof(struct devlink_simple_fw_reporter));
+	if (!devlink)
+		return;
+
+	if (devlink_register(devlink, dev))
+		goto err_free;
+
+	simple_devlink = devlink_priv(devlink);
+	simple_devlink->reporter =
+		devlink_health_reporter_create(devlink, &simple_devlink_health,
+					       0, NULL);
+	if (IS_ERR(simple_devlink->reporter))
+		goto err_unregister;
+
+	mutex_lock(&devlink_simple_fw_reporters_mutex);
+	list_add_tail(&simple_devlink->list, &devlink_simple_fw_reporters);
+	mutex_unlock(&devlink_simple_fw_reporters_mutex);
+
+	return;
+
+err_unregister:
+	devlink_unregister(devlink);
+err_free:
+	devlink_free(devlink);
+}
+EXPORT_SYMBOL_GPL(devlink_simple_fw_reporter_prepare);
+
+void devlink_simple_fw_reporter_cleanup(struct device *dev)
+{
+	struct devlink_simple_fw_reporter *simple_devlink;
+	struct devlink *devlink;
+
+	simple_devlink = devlink_simple_fw_reporter_find_for_dev(dev);
+	if (!simple_devlink)
+		return;
+
+	devlink = priv_to_devlink(simple_devlink);
+	devlink_health_reporter_destroy(simple_devlink->reporter);
+	devlink_unregister(devlink);
+	devlink_free(devlink);
+}
+EXPORT_SYMBOL_GPL(devlink_simple_fw_reporter_cleanup);
-- 
2.25.4