linux-kernel - [PATCH 5.15 092/179] drm/aspeed: Fix vga

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Date:   Mon, 29 Nov 2021 19:18:06 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Oskar Senft <osk@...gle.com>,
        Joel Stanley <joel@....id.au>,
        Jeremy Kerr <jk@...econstruct.com.au>,
        Maxime Ripard <maxime@...no.tech>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.15 092/179] drm/aspeed: Fix vga_pw sysfs output

From: Joel Stanley <joel@....id.au>

[ Upstream commit b4a6aaeaf4aa79f23775f6688a7e8db3ee1c1303 ]

Before the drm driver had support for this file there was a driver that
exposed the contents of the vga password register to userspace. It would
present the entire register instead of interpreting it.

The drm implementation chose to mask of the lower bit, without explaining
why. This breaks the existing userspace, which is looking for 0xa8 in
the lower byte.

Change our implementation to expose the entire register.

Fixes: 696029eb36c0 ("drm/aspeed: Add sysfs for output settings")
Reported-by: Oskar Senft <osk@...gle.com>
Signed-off-by: Joel Stanley <joel@....id.au>
Reviewed-by: Jeremy Kerr <jk@...econstruct.com.au>
Tested-by: Oskar Senft <osk@...gle.com>
Signed-off-by: Maxime Ripard <maxime@...no.tech>
Link: https://patchwork.freedesktop.org/patch/msgid/20211117010145.297253-1-joel@jms.id.au
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/gpu/drm/aspeed/aspeed_gfx_drv.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/aspeed/aspeed_gfx_drv.c b/drivers/gpu/drm/aspeed/aspeed_gfx_drv.c
index b53fee6f1c170..65f172807a0d5 100644
--- a/drivers/gpu/drm/aspeed/aspeed_gfx_drv.c
+++ b/drivers/gpu/drm/aspeed/aspeed_gfx_drv.c
@@ -291,7 +291,7 @@ vga_pw_show(struct device *dev, struct device_attribute *attr, char *buf)
 	if (rc)
 		return rc;
 
-	return sprintf(buf, "%u\n", reg & 1);
+	return sprintf(buf, "%u\n", reg);
 }
 static DEVICE_ATTR_RO(vga_pw);
 
-- 
2.33.0