On Fri, Feb 11, 2022 at 10:19:23AM +0100, Javier Martinez Canillas wrote:
> Add support to convert from XR24 to reversed monochrome for drivers that
> control monochromatic display panels, that only have 1 bit per pixel.
>
> The function does a line-by-line conversion doing an intermediate step
> first from XR24 to 8-bit grayscale and then to reversed monochrome.
>
> The drm_fb_gray8_to_mono_reversed_line() helper was based on code from
> drivers/gpu/drm/tiny/repaper.c driver.
...
> +static void drm_fb_gray8_to_mono_reversed_line(u8 *dst, const u8 *src, unsigned int pixels,
> + unsigned int start_offset, unsigned int end_len)
> +{
> + unsigned int xb, i;
> +
> + for (xb = 0; xb < pixels; xb++) {
> + unsigned int start = 0, end = 8;
> + u8 byte = 0x00;
> + if (xb == 0 && start_offset)
> + start = start_offset;
This is invariant to the loop, can be moved out.
> + if (xb == pixels - 1 && end_len)
> + end = end_len;
Ditto. However it may require to factor out the following loop to a helper.
> + for (i = start; i < end; i++) {
> + unsigned int x = xb * 8 + i;
> +
> + byte >>= 1;
> + if (src[x] >> 7)
> + byte |= BIT(7);
> + }
> + *dst++ = byte;
> + }
> +}
...
> + /*
> + * The reversed mono destination buffer contains 1 bit per pixel
> + * and destination scanlines have to be in multiple of 8 pixels.
> + */
> + if (!dst_pitch)
> + dst_pitch = DIV_ROUND_UP(linepixels, 8);
round_up() ?
> + WARN_ONCE(dst_pitch % 8 != 0, "dst_pitch is not a multiple of 8\n");
I would move this to the if conditional, i.e.
if (dst_pitch)
WARN_ONCE(dst_pitch % 8 != 0, "dst_pitch is not a multiple of 8\n");
else
dst_pitch = round_up(linepixels, 8);
> + /*
> + * The cma memory is write-combined so reads are uncached.
CMA
> + * Speed up by fetching one line at a time.
> + *
> + * Also, format conversion from XR24 to reversed monochrome
> + * are done line-by-line but are converted to 8-bit grayscale
> + * as an intermediate step.
> + *
> + * Allocate a buffer to be used for both copying from the cma
> + * memory and to store the intermediate grayscale line pixels.
> + */
> + src32 = kmalloc(len_src32 + linepixels, GFP_KERNEL);
size_add() ?
> + if (!src32)
> + return;
...
> + /*
> + * For damage handling, it is possible that only parts of the source
> + * buffer is copied and this could lead to start and end pixels that
> + * are not aligned to multiple of 8.
> + *
> + * Calculate if the start and end pixels are not aligned and set the
> + * offsets for the reversed mono line conversion function to adjust.
> + */
> + start_offset = clip->x1 % 8;
> + end_len = clip->x2 % 8;
ALIGN() ?
--
With Best Regards,
Andy Shevchenko
