linux-kernel - [PATCH 2/3] drm/ssd130x: fix ssd132x encoding

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Message-ID: <20250113152752.3369731-3-jkeeping@inmusicbrands.com>
Date: Mon, 13 Jan 2025 15:27:50 +0000
From: John Keeping <jkeeping@...usicbrands.com>
To: Javier Martinez Canillas <javierm@...hat.com>
Cc: John Keeping <jkeeping@...usicbrands.com>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>,
	Simona Vetter <simona@...ll.ch>,
	dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 2/3] drm/ssd130x: fix ssd132x encoding

The ssd132x buffer is encoded one pixel per nibble, with two pixels in
each byte.  When encoding and 8-bit greyscale input, take the top 4-bits
as the value and ensure the two pixels are distinct and do not overwrite
each other.

Signed-off-by: John Keeping <jkeeping@...usicbrands.com>
---
 drivers/gpu/drm/solomon/ssd130x.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/solomon/ssd130x.c b/drivers/gpu/drm/solomon/ssd130x.c
index 2622172228361..64f1123080996 100644
--- a/drivers/gpu/drm/solomon/ssd130x.c
+++ b/drivers/gpu/drm/solomon/ssd130x.c
@@ -880,7 +880,7 @@ static int ssd132x_update_rect(struct ssd130x_device *ssd130x,
 			u8 n1 = buf[i * width + j];
 			u8 n2 = buf[i * width + j + 1];
 
-			data_array[array_idx++] = (n2 << 4) | n1;
+			data_array[array_idx++] = (n2 & 0xf0) | (n1 >> 4);
 		}
 	}
 
-- 
2.47.1