[PATCH v2 1/3] leds: trigger: legtrig-bpf: Add ledtrig-bpf trigger

[Daniel Hodges]

This patch adds a led trigger that interfaces with the bpf subsystem. It
allows for BPF programs to control LED activity through calling bpf
kfuncs. This functionality is useful in giving users a physical
indication that a BPF program has performed an operation such as
handling a packet or probe point.

Signed-off-by: Daniel Hodges <hodges.daniel.scott@xxxxxxxxx>
---
 drivers/leds/trigger/Kconfig       | 10 ++++
 drivers/leds/trigger/Makefile      |  1 +
 drivers/leds/trigger/ledtrig-bpf.c | 73 ++++++++++++++++++++++++++++++
 3 files changed, 84 insertions(+)
 create mode 100644 drivers/leds/trigger/ledtrig-bpf.c

diff --git a/drivers/leds/trigger/Kconfig b/drivers/leds/trigger/Kconfig
index d11d80176fc0..30b0fd3847be 100644
--- a/drivers/leds/trigger/Kconfig
+++ b/drivers/leds/trigger/Kconfig
@@ -152,4 +152,14 @@ config LEDS_TRIGGER_TTY
 
 	  When build as a module this driver will be called ledtrig-tty.
 
+config LEDS_TRIGGER_BPF
+	tristate "LED BPF Trigger"
+	depends on BPF
+	depends on BPF_SYSCALL
+	help
+	  This allows LEDs to be controlled by the BPF subsystem. This trigger
+	  must be used with a loaded BPF program in order to control LED state.
+	  BPF programs can control LED state with kfuncs.
+	  If unsure, say N.
+
 endif # LEDS_TRIGGERS
diff --git a/drivers/leds/trigger/Makefile b/drivers/leds/trigger/Makefile
index 25c4db97cdd4..ac47128d406c 100644
--- a/drivers/leds/trigger/Makefile
+++ b/drivers/leds/trigger/Makefile
@@ -16,3 +16,4 @@ obj-$(CONFIG_LEDS_TRIGGER_NETDEV)	+= ledtrig-netdev.o
 obj-$(CONFIG_LEDS_TRIGGER_PATTERN)	+= ledtrig-pattern.o
 obj-$(CONFIG_LEDS_TRIGGER_AUDIO)	+= ledtrig-audio.o
 obj-$(CONFIG_LEDS_TRIGGER_TTY)		+= ledtrig-tty.o
+obj-$(CONFIG_LEDS_TRIGGER_BPF)		+= ledtrig-bpf.o
diff --git a/drivers/leds/trigger/ledtrig-bpf.c b/drivers/leds/trigger/ledtrig-bpf.c
new file mode 100644
index 000000000000..99cabf816da4
--- /dev/null
+++ b/drivers/leds/trigger/ledtrig-bpf.c
@@ -0,0 +1,73 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * LED BPF Trigger
+ *
+ * Author: Daniel Hodges <hodges.daniel.scott@xxxxxxxxx>
+ */
+
+#include <linux/bpf.h>
+#include <linux/btf.h>
+#include <linux/btf_ids.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/leds.h>
+#include <linux/module.h>
+#include <linux/rcupdate.h>
+
+
+DEFINE_LED_TRIGGER(ledtrig_bpf);
+
+__bpf_kfunc_start_defs();
+__bpf_kfunc void bpf_ledtrig_blink(const char *led_name__str, unsigned long
+		delay_on, unsigned long delay_off, int invert)
+{
+	struct led_classdev *led_cdev;
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(led_cdev, &ledtrig_bpf->led_cdevs, trig_list) {
+		if (strcmp(led_name__str, led_cdev->name) == 0) {
+			led_blink_set_oneshot(led_cdev, &delay_on, &delay_off,
+					invert);
+			break;
+		}
+	}
+	rcu_read_unlock();
+}
+__bpf_kfunc_end_defs();
+
+BTF_KFUNCS_START(ledtrig_bpf_kfunc_ids)
+BTF_ID_FLAGS(func, bpf_ledtrig_blink, KF_TRUSTED_ARGS)
+BTF_KFUNCS_END(ledtrig_bpf_kfunc_ids)
+
+static const struct btf_kfunc_id_set ledtrig_bpf_kfunc_set = {
+	.owner = THIS_MODULE,
+	.set   = &ledtrig_bpf_kfunc_ids,
+};
+
+static int init_bpf(void)
+{
+	int ret;
+
+	ret = register_btf_kfunc_id_set(BPF_PROG_TYPE_UNSPEC,
+			&ledtrig_bpf_kfunc_set);
+	return ret;
+}
+
+static int __init ledtrig_bpf_init(void)
+{
+	led_trigger_register_simple("bpf", &ledtrig_bpf);
+
+	return init_bpf();
+}
+
+static void __exit ledtrig_bpf_exit(void)
+{
+	led_trigger_unregister_simple(ledtrig_bpf);
+}
+
+module_init(ledtrig_bpf_init);
+module_exit(ledtrig_bpf_exit);
+
+MODULE_AUTHOR("Daniel Hodges <hodges.daniel.scott@xxxxxxxxx>");
+MODULE_DESCRIPTION("BPF LED trigger");
+MODULE_LICENSE("GPL v2");
-- 
2.43.2