[RFC PATCH 3/3] lib: sbi: Implement SBI debug console extension

[Anup Patel]

We implement SBI debug console extension as one of the replacement
SBI extensions. This extension is only available when OpenSBI platform
provides a console device to generic library.

Signed-off-by: Anup Patel <apatel at ventanamicro.com>
---
 lib/sbi/Kconfig             |  4 ++++
 lib/sbi/objects.mk          |  1 +
 lib/sbi/sbi_ecall_replace.c | 30 ++++++++++++++++++++++++++++++
 3 files changed, 35 insertions(+)

diff --git a/lib/sbi/Kconfig b/lib/sbi/Kconfig
index df74bba..ef6728b 100644
--- a/lib/sbi/Kconfig
+++ b/lib/sbi/Kconfig
@@ -26,6 +26,10 @@ config SBI_ECALL_PMU
 	bool "Performance Monitoring Unit extension"
 	default y
 
+config SBI_ECALL_DBCN
+	bool "Debug Console extension"
+	default y
+
 config SBI_ECALL_LEGACY
 	bool "SBI v0.1 legacy extensions"
 	default y
diff --git a/lib/sbi/objects.mk b/lib/sbi/objects.mk
index 783c46d..7ccad52 100644
--- a/lib/sbi/objects.mk
+++ b/lib/sbi/objects.mk
@@ -23,6 +23,7 @@ carray-sbi_ecall_exts-y += ecall_base
 carray-sbi_ecall_exts-$(CONFIG_SBI_ECALL_HSM) += ecall_hsm
 carray-sbi_ecall_exts-$(CONFIG_SBI_ECALL_SRST) += ecall_srst
 carray-sbi_ecall_exts-$(CONFIG_SBI_ECALL_PMU) += ecall_pmu
+carray-sbi_ecall_exts-$(CONFIG_SBI_ECALL_DBCN) += ecall_dbcn
 carray-sbi_ecall_exts-$(CONFIG_SBI_ECALL_LEGACY) += ecall_legacy
 carray-sbi_ecall_exts-$(CONFIG_SBI_ECALL_VENDOR) += ecall_vendor
 
diff --git a/lib/sbi/sbi_ecall_replace.c b/lib/sbi/sbi_ecall_replace.c
index 0ea00d6..a092e2f 100644
--- a/lib/sbi/sbi_ecall_replace.c
+++ b/lib/sbi/sbi_ecall_replace.c
@@ -9,6 +9,7 @@
  */
 
 #include <sbi/riscv_asm.h>
+#include <sbi/sbi_console.h>
 #include <sbi/sbi_ecall.h>
 #include <sbi/sbi_ecall_interface.h>
 #include <sbi/sbi_error.h>
@@ -202,3 +203,32 @@ struct sbi_ecall_extension ecall_srst = {
 	.probe = sbi_ecall_srst_probe,
 };
 #endif
+
+#ifdef CONFIG_SBI_ECALL_DBCN
+static int sbi_ecall_dbcn_handler(unsigned long extid, unsigned long funcid,
+				  const struct sbi_trap_regs *regs,
+				  unsigned long *out_val,
+				  struct sbi_trap_info *out_trap)
+{
+	if (funcid == SBI_EXT_DBCN_CONSOLE_PUTS) {
+		/* TODO: sanity check on the physical address range */
+		sbi_nputs((const char *)regs->a1, regs->a0);
+		return 0;
+	}
+
+	return SBI_ENOTSUPP;
+}
+
+static int sbi_ecall_dbcn_probe(unsigned long extid, unsigned long *out_val)
+{
+	*out_val = (sbi_console_get_device()) ? 1 : 0;
+	return 0;
+}
+
+struct sbi_ecall_extension ecall_dbcn = {
+	.extid_start = SBI_EXT_DBCN,
+	.extid_end = SBI_EXT_DBCN,
+	.handle = sbi_ecall_dbcn_handler,
+	.probe = sbi_ecall_dbcn_probe,
+};
+#endif
-- 
2.34.1