[PATCH resend 2/5] video: fbdev: ssd1307fb: Simplify ssd1307fb_update_display()

Geert Uytterhoeven
2021-07-14T14:58:21Z

Simplify the nested loops to handle conversion from linear frame buffer
to ssd1307 page layout:
1. Move last page handling one level up, as the value of "m" is the
same inside a page,
2. array->data[] is filled linearly, so there is no need to
recalculate array_idx over and over again; a simple increment is
sufficient.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
---
drivers/video/fbdev/ssd1307fb.c | 17 ++++++++++-------
1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/drivers/video/fbdev/ssd1307fb.c b/drivers/video/fbdev/ssd1307fb.c
index e6b6263e3bef847f..6d7bd025bca1a175 100644
--- a/drivers/video/fbdev/ssd1307fb.c
+++ b/drivers/video/fbdev/ssd1307fb.c
@@ -158,6 +158,7 @@ static int ssd1307fb_update_display(struct ssd1307fb_par *par)
u8 *vmem = par->info->screen_buffer;
unsigned int line_length = par->info->fix.line_length;
unsigned int pages = DIV_ROUND_UP(par->height, 8);
+ u32 array_idx = 0;
int ret, i, j, k;

array = ssd1307fb_alloc_array(par->width * pages, SSD1307FB_DATA);
@@ -194,19 +195,21 @@ static int ssd1307fb_update_display(struct ssd1307fb_par *par)
*/

for (i = 0; i < pages; i++) {
+ int m = 8;
+
+ /* Last page may be partial */
+ if (i + 1 == pages && par->height % 8)
+ m = par->height % 8;
for (j = 0; j < par->width; j++) {
- int m = 8;
- u32 array_idx = i * par->width + j;
- array->data[array_idx] = 0;
- /* Last page may be partial */
- if (i + 1 == pages && par->height % 8)
- m = par->height % 8;
+ u8 data = 0;
+
for (k = 0; k < m; k++) {
u8 byte = vmem[(8 * i + k) * line_length +
j / 8];
u8 bit = (byte >> (j % 8)) & 1;
- array->data[array_idx] |= bit << k;
+ data |= bit << k;
}
+ array->data[array_idx++] = data;
}
}

--
2.25.1