linux-kernel - [PATCH v2 1/5] apple-gmux: use first bit to check switch state

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20230216122342.5918-2-orlandoch.dev@gmail.com>
Date:   Thu, 16 Feb 2023 23:23:39 +1100
From:   Orlando Chamberlain <orlandoch.dev@...il.com>
To:     Hans de Goede <hdegoede@...hat.com>
Cc:     Mark Gross <markgross@...nel.org>,
        platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org,
        Lukas Wunner <lukas@...ner.de>,
        Seth Forshee <sforshee@...nel.org>,
        Aditya Garg <gargaditya08@...e.com>,
        Aun-Ali Zaidi <admin@...eit.net>,
        Kerem Karabay <kekrby@...il.com>,
        Orlando Chamberlain <orlandoch.dev@...il.com>
Subject: [PATCH v2 1/5] apple-gmux: use first bit to check switch state

On T2 Macs with MMIO gmux, when GMUX_PORT_SWITCH_DISPLAY is read, it can
have values of 2, 3, 4, and 5. Odd values correspond to the discrete gpu,
and even values correspond to the integrated gpu. The current logic is
that only 2 corresponds to IGD, but this doesn't work for T2 Macs.
Instead, check the first bit to determine the connected gpu.

As T2 Macs with gmux only can switch the internal display, it is
untested if this change (or a similar change) would be applicable
to GMUX_PORT_SWITCH_DDC and GMUX_PORT_SWITCH_EXTERNAL.

Signed-off-by: Orlando Chamberlain <orlandoch.dev@...il.com>
---
v1->v2: no change
 drivers/platform/x86/apple-gmux.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/platform/x86/apple-gmux.c b/drivers/platform/x86/apple-gmux.c
index 9333f82cfa8a..ec99e05e532c 100644
--- a/drivers/platform/x86/apple-gmux.c
+++ b/drivers/platform/x86/apple-gmux.c
@@ -346,10 +346,10 @@ static void gmux_read_switch_state(struct apple_gmux_data *gmux_data)
 	else
 		gmux_data->switch_state_ddc = VGA_SWITCHEROO_DIS;
 
-	if (gmux_read8(gmux_data, GMUX_PORT_SWITCH_DISPLAY) == 2)
-		gmux_data->switch_state_display = VGA_SWITCHEROO_IGD;
-	else
+	if (gmux_read8(gmux_data, GMUX_PORT_SWITCH_DISPLAY) & 1)
 		gmux_data->switch_state_display = VGA_SWITCHEROO_DIS;
+	else
+		gmux_data->switch_state_display = VGA_SWITCHEROO_IGD;
 
 	if (gmux_read8(gmux_data, GMUX_PORT_SWITCH_EXTERNAL) == 2)
 		gmux_data->switch_state_external = VGA_SWITCHEROO_IGD;
-- 
2.39.1