Hi
Am 11.02.22 um 12:10 schrieb Andy Shevchenko:
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.
Splitting the loop is much nicer, but leaves corner cases where start and end is in the same byte. Doing this sounds like a premature optimization to me.
Best regards Thomas
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() ?