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() ?
-- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Maxfeldstr. 5, 90409 Nürnberg, Germany (HRB 36809, AG Nürnberg) Geschäftsführer: Ivo Totev
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