[RFC v8 11/20] um: lkl: basic console support

[Hajime Tazaki]

This patch adds a basic structure of console support in kernel.  Write
operations are deferred to the host print operation.

This commit also disables stdio-console of UML when library mode to avoid
conflicts between multiple consoles.

Signed-off-by: Hajime Tazaki <thehajime at gmail.com>
---
 arch/um/drivers/Makefile                |  8 ++++-
 arch/um/lkl/include/uapi/asm/host_ops.h |  9 ++++++
 arch/um/lkl/um/console.c                | 41 +++++++++++++++++++++++++
 3 files changed, 57 insertions(+), 1 deletion(-)
 create mode 100644 arch/um/lkl/um/console.c

diff --git a/arch/um/drivers/Makefile b/arch/um/drivers/Makefile
index ae96c83e312d..dc0d32d62294 100644
--- a/arch/um/drivers/Makefile
+++ b/arch/um/drivers/Makefile
@@ -37,7 +37,13 @@ $(obj)/vde.o: $(obj)/vde_kern.o $(obj)/vde_user.o
 # When the above is fixed, don't forget to add this too!
 #targets += $(obj)/pcap.o
 
-obj-y := stdio_console.o fd.o chan_kern.o chan_user.o line.o
+ifndef CONFIG_UMMODE_LIB
+obj-y := stdio_console.o
+else
+obj-y :=
+endif
+obj-y += fd.o chan_kern.o chan_user.o line.o
+
 obj-$(CONFIG_SSL) += ssl.o
 obj-$(CONFIG_STDERR_CONSOLE) += stderr_console.o
 
diff --git a/arch/um/lkl/include/uapi/asm/host_ops.h b/arch/um/lkl/include/uapi/asm/host_ops.h
index b97aa1099a17..976fc4301b3d 100644
--- a/arch/um/lkl/include/uapi/asm/host_ops.h
+++ b/arch/um/lkl/include/uapi/asm/host_ops.h
@@ -243,4 +243,13 @@ int lkl_tls_set(struct lkl_tls_key *key, void *data);
  */
 void *lkl_tls_get(struct lkl_tls_key *key);
 
+/**
+ * lkl_print - optional operation that receives console messages
+ *
+ * @str: strings to be printed
+ * @len: the length of @str
+ *
+ */
+void lkl_print(const char *str, int len);
+
 #endif
diff --git a/arch/um/lkl/um/console.c b/arch/um/lkl/um/console.c
new file mode 100644
index 000000000000..f2b48dc7ae22
--- /dev/null
+++ b/arch/um/lkl/um/console.c
@@ -0,0 +1,41 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/console.h>
+#include <asm/host_ops.h>
+
+static void console_write(struct console *con, const char *str, unsigned len)
+{
+	lkl_print(str, len);
+}
+
+#ifdef CONFIG_LKL_EARLY_CONSOLE
+static struct console lkl_boot_console = {
+	.name	= "lkl_boot_console",
+	.write	= console_write,
+	.flags	= CON_PRINTBUFFER | CON_BOOT,
+	.index	= -1,
+};
+
+int __init lkl_boot_console_init(void)
+{
+	register_console(&lkl_boot_console);
+	return 0;
+}
+early_initcall(lkl_boot_console_init);
+#endif
+
+static struct console lkl_console = {
+	.name	= "lkl_console",
+	.write	= console_write,
+	.flags	= CON_PRINTBUFFER,
+	.index	= -1,
+};
+
+int __init lkl_console_init(void)
+{
+	register_console(&lkl_console);
+	return 0;
+}
+core_initcall(lkl_console_init);
+
-- 
2.21.0 (Apple Git-122.2)