linux-kernel - [PATCH 3.16 057/328] video: udlfb: Fix unaligned access

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Message-ID: <lsq.1544392233.352734232@decadent.org.uk>
Date:   Sun, 09 Dec 2018 21:50:33 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Ladislav Michl" <ladis@...ux-mips.org>,
        "Bernie Thompson" <bernie@...gable.com>,
        "Bartlomiej Zolnierkiewicz" <b.zolnierkie@...sung.com>
Subject: [PATCH 3.16 057/328] video: udlfb: Fix unaligned access

3.16.62-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Ladislav Michl <ladis@...ux-mips.org>

commit 115e77597efcc94cb1f6cbb7df5cf7ce8feb8632 upstream.

Driver generates lots of alignment trap exceptions on ARM.
Fix that by replacing typecasting of odd addresses with
byte shifting and remove uneccessary typecasting.

Signed-off-by: Ladislav Michl <ladis@...ux-mips.org>
Cc: Bernie Thompson <bernie@...gable.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/video/fbdev/udlfb.c | 23 ++++++++++++-----------
 1 file changed, 12 insertions(+), 11 deletions(-)

--- a/drivers/video/fbdev/udlfb.c
+++ b/drivers/video/fbdev/udlfb.c
@@ -443,9 +443,9 @@ static void dlfb_compress_hline(
 
 		*cmd++ = 0xAF;
 		*cmd++ = 0x6B;
-		*cmd++ = (uint8_t) ((dev_addr >> 16) & 0xFF);
-		*cmd++ = (uint8_t) ((dev_addr >> 8) & 0xFF);
-		*cmd++ = (uint8_t) ((dev_addr) & 0xFF);
+		*cmd++ = dev_addr >> 16;
+		*cmd++ = dev_addr >> 8;
+		*cmd++ = dev_addr;
 
 		cmd_pixels_count_byte = cmd++; /*  we'll know this later */
 		cmd_pixel_start = pixel;
@@ -462,8 +462,8 @@ static void dlfb_compress_hline(
 		while (pixel < cmd_pixel_end) {
 			const uint16_t * const repeating_pixel = pixel;
 
-			*(uint16_t *)cmd = cpu_to_be16p(pixel);
-			cmd += 2;
+			*cmd++ = *pixel >> 8;
+			*cmd++ = *pixel;
 			pixel++;
 
 			if (unlikely((pixel < cmd_pixel_end) &&
@@ -1532,15 +1532,16 @@ static int dlfb_parse_vendor_descriptor(
 			u8 length;
 			u16 key;
 
-			key = le16_to_cpu(*((u16 *) desc));
-			desc += sizeof(u16);
-			length = *desc;
-			desc++;
+			key = *desc++;
+			key |= (u16)*desc++ << 8;
+			length = *desc++;
 
 			switch (key) {
 			case 0x0200: { /* max_area */
-				u32 max_area;
-				max_area = le32_to_cpu(*((u32 *)desc));
+				u32 max_area = *desc++;
+				max_area |= (u32)*desc++ << 8;
+				max_area |= (u32)*desc++ << 16;
+				max_area |= (u32)*desc++ << 24;
 				pr_warn("DL chip limited to %d pixel modes\n",
 					max_area);
 				dev->sku_pixel_limit = max_area;