[PATCH v4 1/4] firmware: arm_sdei: add sdei_is_present()

[Kiryl Shutsemau <kirill@shutemov.name>]

From: "Kiryl Shutsemau (Meta)" <kas@kernel.org>

invoke_sdei_fn() returns -EIO when no SDEI conduit was probed, and the
core warns ("Failed to create event ...") on any registration that hits
that. An optional consumer that registers an event from an unconditional
initcall would therefore make every boot on a non-SDEI system emit that
warning for what is simply absent firmware.

Expose whether SDEI firmware is present so such a consumer can skip
registration -- and the warning -- when there is nothing to talk to.

Signed-off-by: Kiryl Shutsemau (Meta) <kas@kernel.org>
---
 drivers/firmware/arm_sdei.c | 10 ++++++++++
 include/linux/arm_sdei.h    |  3 +++
 2 files changed, 13 insertions(+)

diff --git a/drivers/firmware/arm_sdei.c b/drivers/firmware/arm_sdei.c
index f39ed7ba3a38..c161cf263547 100644
--- a/drivers/firmware/arm_sdei.c
+++ b/drivers/firmware/arm_sdei.c
@@ -339,6 +339,16 @@ static void _ipi_unmask_cpu(void *ignored)
 	sdei_unmask_local_cpu();
 }
 
+/*
+ * Was SDEI firmware probed and is it usable?  Lets optional consumers skip
+ * registering an event -- and the warning a failed registration emits -- on
+ * systems with no SDEI.
+ */
+bool sdei_is_present(void)
+{
+	return sdei_firmware_call;
+}
+
 static void _ipi_private_reset(void *ignored)
 {
 	int err;
diff --git a/include/linux/arm_sdei.h b/include/linux/arm_sdei.h
index f652a5028b59..b07113eeeff7 100644
--- a/include/linux/arm_sdei.h
+++ b/include/linux/arm_sdei.h
@@ -37,6 +37,9 @@ int sdei_event_unregister(u32 event_num);
 int sdei_event_enable(u32 event_num);
 int sdei_event_disable(u32 event_num);
 
+/* Was SDEI firmware probed and usable? */
+bool sdei_is_present(void);
+
 /* GHES register/unregister helpers */
 int sdei_register_ghes(struct ghes *ghes, sdei_event_callback *normal_cb,
 		       sdei_event_callback *critical_cb);
-- 
2.54.0