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    SubjectRe: [PATCH v4 2/6] drm/format-helper: Add drm_fb_xrgb8888_to_mono_reversed()
    From
    Hi

    Am 11.02.22 um 10:19 schrieb Javier Martinez Canillas:
    > 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.
    >
    > Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
    > Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
    > ---
    >
    > Changes in v4:
    > - Rename end_offset to end_len (Thomas Zimmermann)
    > - Warn once if dst_pitch is not a multiple of 8 (Thomas Zimmermann)
    > - Drop drm_fb_gray8_to_mono_reversed() that's not used (Thomas Zimmermann)
    > - Allocate single buffer for both copy cma memory and gray8 (Thomas Zimmermann)
    > - Add Thomas Zimmermann Reviewed-by tag to patch adding XR24 -> mono helper.
    >
    > Changes in v3:
    > - Also add a drm_fb_xrgb8888_to_mono_reversed() helper (Thomas Zimmermann)
    > - Split lines copy to drm_fb_gray8_to_mono_reversed_line() (Thomas Zimmermann)
    > - Handle case where the source buffer is not aligned to 8 (Thomas Zimmermann)
    >
    > drivers/gpu/drm/drm_format_helper.c | 107 ++++++++++++++++++++++++++++
    > include/drm/drm_format_helper.h | 4 ++
    > 2 files changed, 111 insertions(+)
    >
    > diff --git a/drivers/gpu/drm/drm_format_helper.c b/drivers/gpu/drm/drm_format_helper.c
    > index b981712623d3..ec4e3724ee79 100644
    > --- a/drivers/gpu/drm/drm_format_helper.c
    > +++ b/drivers/gpu/drm/drm_format_helper.c
    > @@ -591,3 +591,110 @@ int drm_fb_blit_toio(void __iomem *dst, unsigned int dst_pitch, uint32_t dst_for
    > return -EINVAL;
    > }
    > EXPORT_SYMBOL(drm_fb_blit_toio);
    > +
    > +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;
    > +
    > + if (xb == pixels - 1 && end_len)
    > + end = end_len;
    > +
    > + for (i = start; i < end; i++) {
    > + unsigned int x = xb * 8 + i;
    > +
    > + byte >>= 1;
    > + if (src[x] >> 7)
    > + byte |= BIT(7);
    > + }
    > + *dst++ = byte;
    > + }
    > +}
    > +
    > +/**
    > + * drm_fb_xrgb8888_to_mono_reversed - Convert XRGB8888 to reversed monochrome
    > + * @dst: reversed monochrome destination buffer
    > + * @dst_pitch: Number of bytes between two consecutive scanlines within dst
    > + * @src: XRGB8888 source buffer
    > + * @fb: DRM framebuffer
    > + * @clip: Clip rectangle area to copy
    > + *
    > + * DRM doesn't have native monochrome support.
    > + * Such drivers can announce the commonly supported XR24 format to userspace
    > + * and use this function to convert to the native format.
    > + *
    > + * This function uses drm_fb_xrgb8888_to_gray8() to convert to grayscale and
    > + * then the result is converted from grayscale to reversed monohrome.
    > + */
    > +void drm_fb_xrgb8888_to_mono_reversed(void *dst, unsigned int dst_pitch, const void *vaddr,
    > + const struct drm_framebuffer *fb, const struct drm_rect *clip)
    > +{
    > + unsigned int linepixels = drm_rect_width(clip);
    > + unsigned int lines = clip->y2 - clip->y1;
    > + unsigned int cpp = fb->format->cpp[0];
    > + unsigned int len_src32 = linepixels * cpp;
    > + unsigned int start_offset, end_len;
    > + unsigned int y;
    > + u8 *mono = dst, *gray8;
    > + u32 *src32;
    > +
    > + if (WARN_ON(fb->format->format != DRM_FORMAT_XRGB8888))
    > + return;

    These WARN macros are deprecated. Use drm_warn, drm_WARN_ONCE, etc instead.

    Best regards
    Thomas

    > +
    > + /*
    > + * 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);
    > +
    > + WARN_ONCE(dst_pitch % 8 != 0, "dst_pitch is not a multiple of 8\n");
    > +
    > + /*
    > + * The cma memory is write-combined so reads are uncached.
    > + * 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);
    > + if (!src32)
    > + return;
    > +
    > + gray8 = (u8 *)src32 + len_src32;
    > +
    > + /*
    > + * 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;
    > +
    > + vaddr += clip_offset(clip, fb->pitches[0], cpp);
    > + for (y = 0; y < lines; y++) {
    > + src32 = memcpy(src32, vaddr, len_src32);
    > + drm_fb_xrgb8888_to_gray8_line(gray8, src32, linepixels);
    > + drm_fb_gray8_to_mono_reversed_line(mono, gray8, dst_pitch,
    > + start_offset, end_len);
    > + vaddr += fb->pitches[0];
    > + mono += dst_pitch;
    > + }
    > +
    > + kfree(src32);
    > +}
    > +EXPORT_SYMBOL(drm_fb_xrgb8888_to_mono_reversed);
    > diff --git a/include/drm/drm_format_helper.h b/include/drm/drm_format_helper.h
    > index b30ed5de0a33..0b0937c0b2f6 100644
    > --- a/include/drm/drm_format_helper.h
    > +++ b/include/drm/drm_format_helper.h
    > @@ -43,4 +43,8 @@ int drm_fb_blit_toio(void __iomem *dst, unsigned int dst_pitch, uint32_t dst_for
    > const void *vmap, const struct drm_framebuffer *fb,
    > const struct drm_rect *rect);
    >
    > +void drm_fb_xrgb8888_to_mono_reversed(void *dst, unsigned int dst_pitch, const void *src,
    > + const struct drm_framebuffer *fb,
    > + const struct drm_rect *clip);
    > +
    > #endif /* __LINUX_DRM_FORMAT_HELPER_H */

    --
    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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