Hi Marcus,
On Wed, 23 Apr 2025 at 21:04, Marcus Folkesson
<marcus.folkes...@gmail.com> wrote:
> Sitronix ST7571 is a 4bit gray scale dot matrix LCD controller.
> The controller has a SPI, I2C and 8bit parallel interface, this
> driver is for the I2C interface only.
>
> Reviewed-by: Thomas Zimmermann <tzimmrm...@suse.de>
> Reviewed-by: Javier Martinez Canillas <javi...@redhat.com>
> Signed-off-by: Marcus Folkesson <marcus.folkes...@gmail.com>
Thanks for your patch, which is now commit 4b35f0f41ee29505
("drm/st7571-i2c: add support for Sitronix ST7571 LCD controller")
in drm-misc-next.
> --- /dev/null
> +++ b/drivers/gpu/drm/tiny/st7571-i2c.c
> +static int st7571_fb_update_rect_grayscale(struct drm_framebuffer *fb,
> struct drm_rect *rect)
> +{
> + struct st7571_device *st7571 = drm_to_st7571(fb->dev);
> + u32 format = fb->format->format;
> + char *row = st7571->row;
> + int x1;
> + int x2;
> +
> + /* Align y to display page boundaries */
> + rect->y1 = round_down(rect->y1, ST7571_PAGE_HEIGHT);
> + rect->y2 = min_t(unsigned int, round_up(rect->y2,
> ST7571_PAGE_HEIGHT), st7571->nlines);
> +
> + switch (format) {
> + case DRM_FORMAT_XRGB8888:
> + /* Threated as monochrome (R1) */
> + fallthrough;
> + case DRM_FORMAT_R1:
> + x1 = rect->x1;
> + x2 = rect->x2;
> + break;
> + case DRM_FORMAT_R2:
> + x1 = rect->x1 * 2;
> + x2 = rect->x2 * 2;
> + break;
> + }
> +
> + for (int y = rect->y1; y < rect->y2; y += ST7571_PAGE_HEIGHT) {
> + for (int x = x1; x < x2; x++)
> + row[x] = st7571_transform_xy(st7571->hwbuf, x, y);
> +
> + st7571_set_position(st7571, rect->x1, y);
> +
> + /* TODO: Investige why we can't write multiple bytes at once
> */
> + for (int x = x1; x < x2; x++) {
> + regmap_bulk_write(st7571->regmap, ST7571_DATA_MODE,
> row + x, 1);
> +
> + /*
> + * As the display supports grayscale, all pixels must
> be written as two bits
> + * even if the format is monochrome.
> + *
> + * The bit values maps to the following grayscale:
> + * 0 0 = White
> + * 0 1 = Light gray
> + * 1 0 = Dark gray
> + * 1 1 = Black
That is not R2, but D2?
include/uapi/drm/drm_fourcc.h:
/* 2 bpp Red (direct relationship between channel value and brightness) */
#define DRM_FORMAT_R2 fourcc_code('R', '2', ' ', ' ')
/* [7:0] R0:R1:R2:R3 2:2:2:2 four pixels/byte */
/* 2 bpp Darkness (inverse relationship between channel value and
brightness) */
#define DRM_FORMAT_D2 fourcc_code('D', '2', ' ', ' ')
/* [7:0] D0:D1:D2:D3 2:2:2:2 four pixels/byte */
So the driver actually supports D1 and D2, and XRGB8888 should be
inverted while converting to monochrome (and grayscale, which is not
yet implemented).
> + *
> + * For monochrome formats, write the same value twice
> to get
> + * either a black or white pixel.
> + */
> + if (format == DRM_FORMAT_R1 || format ==
> DRM_FORMAT_XRGB8888)
> + regmap_bulk_write(st7571->regmap,
> ST7571_DATA_MODE, row + x, 1);
> + }
> + }
> +
> + return 0;
> +}
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- ge...@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
