[PATCH][RESEND] acpi/x86: add a kernel parameter to disable ACPI BGRT

Alex Hung
2020-03-04T22:55:55Z

BGRT is for displaying seamless OEM logo from booting to login screen;
however, this mechanism does not always work well on all configurations
and the OEM logo can be displayed multiple times. This looks worse than
without BGRT enabled.

This patch adds a kernel parameter to disable BGRT in boot time. This is
easier than re-compiling a kernel with CONFIG_ACPI_BGRT disabled.

Signed-off-by: Alex Hung <alex.hung@canonical.com>
---

* Resend to include linux-acpi emailing list

Documentation/admin-guide/kernel-parameters.txt | 3 +++
arch/x86/kernel/acpi/boot.c | 10 +++++++++-
2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index ffff776..55c5b2f 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -442,6 +442,9 @@
bert_disable [ACPI]
Disable BERT OS support on buggy BIOSes.

+ bgrt_disable [ACPI][X86]
+ Disable BGRT to avoid flickering OEM logo.
+
bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
bttv.radio= Most important insmod options are available as
kernel args too.
diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
index 04205ce..d1757ce 100644
--- a/arch/x86/kernel/acpi/boot.c
+++ b/arch/x86/kernel/acpi/boot.c
@@ -45,6 +45,7 @@ EXPORT_SYMBOL(acpi_disabled);
#define PREFIX "ACPI: "

int acpi_noirq; /* skip ACPI IRQ initialization */
+int acpi_nobgrt; /* skip ACPI BGRT */
int acpi_pci_disabled; /* skip ACPI PCI scan and IRQ initialization */
EXPORT_SYMBOL(acpi_pci_disabled);

@@ -1619,7 +1620,7 @@ int __init acpi_boot_init(void)
acpi_process_madt();

acpi_table_parse(ACPI_SIG_HPET, acpi_parse_hpet);
- if (IS_ENABLED(CONFIG_ACPI_BGRT))
+ if (IS_ENABLED(CONFIG_ACPI_BGRT) && !acpi_nobgrt)
acpi_table_parse(ACPI_SIG_BGRT, acpi_parse_bgrt);

if (!acpi_noirq)
@@ -1671,6 +1672,13 @@ static int __init parse_acpi(char *arg)
}
early_param("acpi", parse_acpi);

+static int __init parse_acpi_bgrt(char *arg)
+{
+ acpi_nobgrt = true;
+ return 0;
+}
+early_param("bgrt_disable", parse_acpi_bgrt);
+
/* FIXME: Using pci= for an ACPI parameter is a travesty. */
static int __init parse_pci(char *arg)
{
--
2.7.4