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

Ben Hutchings
2018-12-09T22:04:46Z

From: Ladislav Michl <ladis@linux-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@linux-mips.org>
Cc: Bernie Thompson <bernie@plugable.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.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;