[PATCH v3 1/3] efi_loader: Avoid overwriting previous outputs on console screen clearing

[Jan Kiszka]

From: Jan Kiszka <jan.kiszka at siemens.com>

Before clearing the screen, ensure that no previous output of firmware
or UEFI programs will be overwritten on serial devices or other
streaming consoles. This helps generating complete boot logs.

Tested regarding multi-output against qemu-x86_defconfig.

Signed-off-by: Jan Kiszka <jan.kiszka at siemens.com>
---
 lib/efi_loader/efi_console.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/lib/efi_loader/efi_console.c b/lib/efi_loader/efi_console.c
index 4d08dd3763a..6ce0fcc168d 100644
--- a/lib/efi_loader/efi_console.c
+++ b/lib/efi_loader/efi_console.c
@@ -461,10 +461,16 @@ static efi_status_t EFIAPI efi_cout_set_attribute(
 }
 
 /**
- * efi_cout_clear_screen() - clear screen
+ * efi_clear_screen() - clear screen
  */
 static void efi_clear_screen(void)
 {
+	unsigned int row;
+
+	/* Avoid overwriting previous outputs on streaming consoles */
+	for (row = 1; row < efi_cout_modes[efi_con_mode.mode].rows; row++)
+		printf("\n");
+
 	/*
 	 * The Linux console wants both a clear and a home command. The video
 	 * uclass does not support <ESC>[H without coordinates, yet.
-- 
2.35.3