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drm/format-helper: Add drm_fb_xrgb8888_to_mono_reversed()

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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>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Maxime Ripard <maxime@cerno.tech>
Link: https://patchwork.freedesktop.org/patch/msgid/20220214133710.3278506-3-javierm@redhat.com
This commit is contained in:
Javier Martinez Canillas 2022-02-14 14:37:06 +01:00
parent 4a564e59bf
commit bcf8b616de
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GPG Key ID: C751E590D63F3D69
2 changed files with 114 additions and 0 deletions
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110
drivers/gpu/drm/drm_format_helper.c
View File

@ -12,9 +12,11 @@
#include <linux/slab.h>
#include <linux/io.h>
#include <drm/drm_device.h>
#include <drm/drm_format_helper.h>
#include <drm/drm_framebuffer.h>
#include <drm/drm_fourcc.h>
#include <drm/drm_print.h>
#include <drm/drm_rect.h>
static unsigned int clip_offset(const struct drm_rect *clip, unsigned int pitch, unsigned int cpp)
@ -591,3 +593,111 @@ 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;
struct drm_device *dev = fb->dev;
unsigned int start_offset, end_len;
unsigned int y;
u8 *mono = dst, *gray8;
u32 *src32;
if (drm_WARN_ON(dev, fb->format->format != DRM_FORMAT_XRGB8888))
return;
/*
* 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);
drm_WARN_ONCE(dev, 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);

4
include/drm/drm_format_helper.h
View File

@ -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 */