drivers/gpu/drm/drm_format_helper.c - linux/kernel/git/gregkh/driver-core - Git at Google

 // SPDX-License-Identifier: GPL-2.0 or MIT
 /*
  * Copyright (C) 2016 Noralf Trønnes
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation; either version 2 of the License, or
  * (at your option) any later version.
  */

 #include <linux/module.h>
 #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)
 {
 	return clip->y1 * pitch + clip->x1 * cpp;
 }

 /**
  * drm_fb_clip_offset - Returns the clipping rectangles byte-offset in a framebuffer
  * @pitch: Framebuffer line pitch in byte
  * @format: Framebuffer format
  * @clip: Clip rectangle
  *
  * Returns:
  * The byte offset of the clip rectangle's top-left corner within the framebuffer.
  */
 unsigned int drm_fb_clip_offset(unsigned int pitch, const struct drm_format_info *format,
 				const struct drm_rect *clip)
 {
 	return clip_offset(clip, pitch, format->cpp[0]);
 }
 EXPORT_SYMBOL(drm_fb_clip_offset);

 /* TODO: Make this functon work with multi-plane formats. */
 static int drm_fb_xfrm(void *dst, unsigned long dst_pitch, unsigned long dst_pixsize,
 		       const void *vaddr, const struct drm_framebuffer *fb,
 		       const struct drm_rect *clip, bool vaddr_cached_hint,
 		       void (*xfrm_line)(void *dbuf, const void *sbuf, unsigned int npixels))
 {
 	unsigned long linepixels = drm_rect_width(clip);
 	unsigned long lines = drm_rect_height(clip);
 	size_t sbuf_len = linepixels * fb->format->cpp[0];
 	void *stmp = NULL;
 	unsigned long i;
 	const void *sbuf;

 	/*
 	 * Some source buffers, such as CMA memory, use write-combine
 	 * caching, so reads are uncached. Speed up access by fetching
 	 * one line at a time.
 	 */
 	if (!vaddr_cached_hint) {
 		stmp = kmalloc(sbuf_len, GFP_KERNEL);
 		if (!stmp)
 			return -ENOMEM;
 	}

 	if (!dst_pitch)
 		dst_pitch = drm_rect_width(clip) * dst_pixsize;
 	vaddr += clip_offset(clip, fb->pitches[0], fb->format->cpp[0]);

 	for (i = 0; i < lines; ++i) {
 		if (stmp)
 			sbuf = memcpy(stmp, vaddr, sbuf_len);
 		else
 			sbuf = vaddr;
 		xfrm_line(dst, sbuf, linepixels);
 		vaddr += fb->pitches[0];
 		dst += dst_pitch;
 	}

 	kfree(stmp);

 	return 0;
 }

 /* TODO: Make this functon work with multi-plane formats. */
 static int drm_fb_xfrm_toio(void __iomem *dst, unsigned long dst_pitch, unsigned long dst_pixsize,
 			    const void *vaddr, const struct drm_framebuffer *fb,
 			    const struct drm_rect *clip, bool vaddr_cached_hint,
 			    void (*xfrm_line)(void *dbuf, const void *sbuf, unsigned int npixels))
 {
 	unsigned long linepixels = drm_rect_width(clip);
 	unsigned long lines = drm_rect_height(clip);
 	size_t dbuf_len = linepixels * dst_pixsize;
 	size_t stmp_off = round_up(dbuf_len, ARCH_KMALLOC_MINALIGN); /* for sbuf alignment */
 	size_t sbuf_len = linepixels * fb->format->cpp[0];
 	void *stmp = NULL;
 	unsigned long i;
 	const void *sbuf;
 	void *dbuf;

 	if (vaddr_cached_hint) {
 		dbuf = kmalloc(dbuf_len, GFP_KERNEL);
 	} else {
 		dbuf = kmalloc(stmp_off + sbuf_len, GFP_KERNEL);
 		stmp = dbuf + stmp_off;
 	}
 	if (!dbuf)
 		return -ENOMEM;

 	if (!dst_pitch)
 		dst_pitch = linepixels * dst_pixsize;
 	vaddr += clip_offset(clip, fb->pitches[0], fb->format->cpp[0]);

 	for (i = 0; i < lines; ++i) {
 		if (stmp)
 			sbuf = memcpy(stmp, vaddr, sbuf_len);
 		else
 			sbuf = vaddr;
 		xfrm_line(dbuf, sbuf, linepixels);
 		memcpy_toio(dst, dbuf, dbuf_len);
 		vaddr += fb->pitches[0];
 		dst += dst_pitch;
 	}

 	kfree(dbuf);

 	return 0;
 }

 /**
  * drm_fb_memcpy - Copy clip buffer
  * @dst: Destination buffer
  * @dst_pitch: Number of bytes between two consecutive scanlines within dst
  * @vaddr: Source buffer
  * @fb: DRM framebuffer
  * @clip: Clip rectangle area to copy
  *
  * This function does not apply clipping on dst, i.e. the destination
  * is at the top-left corner.
  */
 void drm_fb_memcpy(void *dst, unsigned int dst_pitch, const void *vaddr,
 		   const struct drm_framebuffer *fb, const struct drm_rect *clip)
 {
 	unsigned int cpp = fb->format->cpp[0];
 	size_t len = (clip->x2 - clip->x1) * cpp;
 	unsigned int y, lines = clip->y2 - clip->y1;

 	if (!dst_pitch)
 		dst_pitch = len;

 	vaddr += clip_offset(clip, fb->pitches[0], cpp);
 	for (y = 0; y < lines; y++) {
 		memcpy(dst, vaddr, len);
 		vaddr += fb->pitches[0];
 		dst += dst_pitch;
 	}
 }
 EXPORT_SYMBOL(drm_fb_memcpy);

 /**
  * drm_fb_memcpy_toio - Copy clip buffer
  * @dst: Destination buffer (iomem)
  * @dst_pitch: Number of bytes between two consecutive scanlines within dst
  * @vaddr: Source buffer
  * @fb: DRM framebuffer
  * @clip: Clip rectangle area to copy
  *
  * This function does not apply clipping on dst, i.e. the destination
  * is at the top-left corner.
  */
 void drm_fb_memcpy_toio(void __iomem *dst, unsigned int dst_pitch, const void *vaddr,
 			const struct drm_framebuffer *fb, const struct drm_rect *clip)
 {
 	unsigned int cpp = fb->format->cpp[0];
 	size_t len = (clip->x2 - clip->x1) * cpp;
 	unsigned int y, lines = clip->y2 - clip->y1;

 	if (!dst_pitch)
 		dst_pitch = len;

 	vaddr += clip_offset(clip, fb->pitches[0], cpp);
 	for (y = 0; y < lines; y++) {
 		memcpy_toio(dst, vaddr, len);
 		vaddr += fb->pitches[0];
 		dst += dst_pitch;
 	}
 }
 EXPORT_SYMBOL(drm_fb_memcpy_toio);

 static void drm_fb_swab16_line(void *dbuf, const void *sbuf, unsigned int pixels)
 {
 	u16 *dbuf16 = dbuf;
 	const u16 *sbuf16 = sbuf;
 	const u16 *send16 = sbuf16 + pixels;

 	while (sbuf16 < send16)
 		*dbuf16++ = swab16(*sbuf16++);
 }

 static void drm_fb_swab32_line(void *dbuf, const void *sbuf, unsigned int pixels)
 {
 	u32 *dbuf32 = dbuf;
 	const u32 *sbuf32 = sbuf;
 	const u32 *send32 = sbuf32 + pixels;

 	while (sbuf32 < send32)
 		*dbuf32++ = swab32(*sbuf32++);
 }

 /**
  * drm_fb_swab - Swap bytes into clip buffer
  * @dst: Destination buffer
  * @dst_pitch: Number of bytes between two consecutive scanlines within dst
  * @src: Source buffer
  * @fb: DRM framebuffer
  * @clip: Clip rectangle area to copy
  * @cached: Source buffer is mapped cached (eg. not write-combined)
  *
  * If @cached is false a temporary buffer is used to cache one pixel line at a
  * time to speed up slow uncached reads.
  *
  * This function does not apply clipping on dst, i.e. the destination
  * is at the top-left corner.
  */
 void drm_fb_swab(void *dst, unsigned int dst_pitch, const void *src,
 		 const struct drm_framebuffer *fb, const struct drm_rect *clip,
 		 bool cached)
 {
 	u8 cpp = fb->format->cpp[0];

 	switch (cpp) {
 	case 4:
 		drm_fb_xfrm(dst, dst_pitch, cpp, src, fb, clip, cached, drm_fb_swab32_line);
 		break;
 	case 2:
 		drm_fb_xfrm(dst, dst_pitch, cpp, src, fb, clip, cached, drm_fb_swab16_line);
 		break;
 	default:
 		drm_warn_once(fb->dev, "Format %p4cc has unsupported pixel size.\n",
 			      &fb->format->format);
 		break;
 	}
 }
 EXPORT_SYMBOL(drm_fb_swab);

 static void drm_fb_xrgb8888_to_rgb332_line(void *dbuf, const void *sbuf, unsigned int pixels)
 {
 	u8 *dbuf8 = dbuf;
 	const __le32 *sbuf32 = sbuf;
 	unsigned int x;
 	u32 pix;

 	for (x = 0; x < pixels; x++) {
 		pix = le32_to_cpu(sbuf32[x]);
 		dbuf8[x] = ((pix & 0x00e00000) >> 16) |
 			   ((pix & 0x0000e000) >> 11) |
 			   ((pix & 0x000000c0) >> 6);
 	}
 }

 /**
  * drm_fb_xrgb8888_to_rgb332 - Convert XRGB8888 to RGB332 clip buffer
  * @dst: RGB332 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
  *
  * Drivers can use this function for RGB332 devices that don't natively support XRGB8888.
  */
 void drm_fb_xrgb8888_to_rgb332(void *dst, unsigned int dst_pitch, const void *src,
 			       const struct drm_framebuffer *fb, const struct drm_rect *clip)
 {
 	drm_fb_xfrm(dst, dst_pitch, 1, src, fb, clip, false, drm_fb_xrgb8888_to_rgb332_line);
 }
 EXPORT_SYMBOL(drm_fb_xrgb8888_to_rgb332);

 static void drm_fb_xrgb8888_to_rgb565_line(void *dbuf, const void *sbuf, unsigned int pixels)
 {
 	u16 *dbuf16 = dbuf;
 	const u32 *sbuf32 = sbuf;
 	unsigned int x;
 	u16 val16;

 	for (x = 0; x < pixels; x++) {
 		val16 = ((sbuf32[x] & 0x00F80000) >> 8) |
 			((sbuf32[x] & 0x0000FC00) >> 5) |
 			((sbuf32[x] & 0x000000F8) >> 3);
 		dbuf16[x] = val16;
 	}
 }

 static void drm_fb_xrgb8888_to_rgb565_swab_line(void *dbuf, const void *sbuf,
 						unsigned int pixels)
 {
 	u16 *dbuf16 = dbuf;
 	const u32 *sbuf32 = sbuf;
 	unsigned int x;
 	u16 val16;

 	for (x = 0; x < pixels; x++) {
 		val16 = ((sbuf32[x] & 0x00F80000) >> 8) |
 			((sbuf32[x] & 0x0000FC00) >> 5) |
 			((sbuf32[x] & 0x000000F8) >> 3);
 		dbuf16[x] = swab16(val16);
 	}
 }

 /**
  * drm_fb_xrgb8888_to_rgb565 - Convert XRGB8888 to RGB565 clip buffer
  * @dst: RGB565 destination buffer
  * @dst_pitch: Number of bytes between two consecutive scanlines within dst
  * @vaddr: XRGB8888 source buffer
  * @fb: DRM framebuffer
  * @clip: Clip rectangle area to copy
  * @swab: Swap bytes
  *
  * Drivers can use this function for RGB565 devices that don't natively
  * support XRGB8888.
  */
 void drm_fb_xrgb8888_to_rgb565(void *dst, unsigned int dst_pitch, const void *vaddr,
 			       const struct drm_framebuffer *fb, const struct drm_rect *clip,
 			       bool swab)
 {
 	if (swab)
 		drm_fb_xfrm(dst, dst_pitch, 2, vaddr, fb, clip, false,
 			    drm_fb_xrgb8888_to_rgb565_swab_line);
 	else
 		drm_fb_xfrm(dst, dst_pitch, 2, vaddr, fb, clip, false,
 			    drm_fb_xrgb8888_to_rgb565_line);
 }
 EXPORT_SYMBOL(drm_fb_xrgb8888_to_rgb565);

 /**
  * drm_fb_xrgb8888_to_rgb565_toio - Convert XRGB8888 to RGB565 clip buffer
  * @dst: RGB565 destination buffer (iomem)
  * @dst_pitch: Number of bytes between two consecutive scanlines within dst
  * @vaddr: XRGB8888 source buffer
  * @fb: DRM framebuffer
  * @clip: Clip rectangle area to copy
  * @swab: Swap bytes
  *
  * Drivers can use this function for RGB565 devices that don't natively
  * support XRGB8888.
  */
 void drm_fb_xrgb8888_to_rgb565_toio(void __iomem *dst, unsigned int dst_pitch,
 				    const void *vaddr, const struct drm_framebuffer *fb,
 				    const struct drm_rect *clip, bool swab)
 {
 	if (swab)
 		drm_fb_xfrm_toio(dst, dst_pitch, 2, vaddr, fb, clip, false,
 				 drm_fb_xrgb8888_to_rgb565_swab_line);
 	else
 		drm_fb_xfrm_toio(dst, dst_pitch, 2, vaddr, fb, clip, false,
 				 drm_fb_xrgb8888_to_rgb565_line);
 }
 EXPORT_SYMBOL(drm_fb_xrgb8888_to_rgb565_toio);

 static void drm_fb_xrgb8888_to_rgb888_line(void *dbuf, const void *sbuf, unsigned int pixels)
 {
 	u8 *dbuf8 = dbuf;
 	const u32 *sbuf32 = sbuf;
 	unsigned int x;

 	for (x = 0; x < pixels; x++) {
 		*dbuf8++ = (sbuf32[x] & 0x000000FF) >>  0;
 		*dbuf8++ = (sbuf32[x] & 0x0000FF00) >>  8;
 		*dbuf8++ = (sbuf32[x] & 0x00FF0000) >> 16;
 	}
 }

 /**
  * drm_fb_xrgb8888_to_rgb888 - Convert XRGB8888 to RGB888 clip buffer
  * @dst: RGB888 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
  *
  * Drivers can use this function for RGB888 devices that don't natively
  * support XRGB8888.
  */
 void drm_fb_xrgb8888_to_rgb888(void *dst, unsigned int dst_pitch, const void *src,
 			       const struct drm_framebuffer *fb, const struct drm_rect *clip)
 {
 	drm_fb_xfrm(dst, dst_pitch, 3, src, fb, clip, false, drm_fb_xrgb8888_to_rgb888_line);
 }
 EXPORT_SYMBOL(drm_fb_xrgb8888_to_rgb888);

 /**
  * drm_fb_xrgb8888_to_rgb888_toio - Convert XRGB8888 to RGB888 clip buffer
  * @dst: RGB565 destination buffer (iomem)
  * @dst_pitch: Number of bytes between two consecutive scanlines within dst
  * @vaddr: XRGB8888 source buffer
  * @fb: DRM framebuffer
  * @clip: Clip rectangle area to copy
  *
  * Drivers can use this function for RGB888 devices that don't natively
  * support XRGB8888.
  */
 void drm_fb_xrgb8888_to_rgb888_toio(void __iomem *dst, unsigned int dst_pitch,
 				    const void *vaddr, const struct drm_framebuffer *fb,
 				    const struct drm_rect *clip)
 {
 	drm_fb_xfrm_toio(dst, dst_pitch, 3, vaddr, fb, clip, false,
 			 drm_fb_xrgb8888_to_rgb888_line);
 }
 EXPORT_SYMBOL(drm_fb_xrgb8888_to_rgb888_toio);

 static void drm_fb_rgb565_to_xrgb8888_line(void *dbuf, const void *sbuf, unsigned int pixels)
 {
 	u32 *dbuf32 = dbuf;
 	const u16 *sbuf16 = sbuf;
 	unsigned int x;

 	for (x = 0; x < pixels; x++, ++sbuf16, ++dbuf32) {
 		u32 val32 = ((*sbuf16 & 0xf800) << 8) |
 			    ((*sbuf16 & 0x07e0) << 5) |
 			    ((*sbuf16 & 0x001f) << 3);
 		*dbuf32 = 0xff000000 | val32 |
 			  ((val32 >> 3) & 0x00070007) |
 			  ((val32 >> 2) & 0x00000300);
 	}
 }

 static void drm_fb_rgb565_to_xrgb8888_toio(void __iomem *dst, unsigned int dst_pitch,
 					   const void *vaddr, const struct drm_framebuffer *fb,
 					   const struct drm_rect *clip)
 {
 	drm_fb_xfrm_toio(dst, dst_pitch, 4, vaddr, fb, clip, false,
 			 drm_fb_rgb565_to_xrgb8888_line);
 }

 static void drm_fb_rgb888_to_xrgb8888_line(void *dbuf, const void *sbuf, unsigned int pixels)
 {
 	u32 *dbuf32 = dbuf;
 	const u8 *sbuf8 = sbuf;
 	unsigned int x;

 	for (x = 0; x < pixels; x++) {
 		u8 r = *sbuf8++;
 		u8 g = *sbuf8++;
 		u8 b = *sbuf8++;
 		*dbuf32++ = 0xff000000 | (r << 16) | (g << 8) | b;
 	}
 }

 static void drm_fb_rgb888_to_xrgb8888_toio(void __iomem *dst, unsigned int dst_pitch,
 					   const void *vaddr, const struct drm_framebuffer *fb,
 					   const struct drm_rect *clip)
 {
 	drm_fb_xfrm_toio(dst, dst_pitch, 4, vaddr, fb, clip, false,
 			 drm_fb_rgb888_to_xrgb8888_line);
 }

 static void drm_fb_xrgb8888_to_xrgb2101010_line(void *dbuf, const void *sbuf, unsigned int pixels)
 {
 	u32 *dbuf32 = dbuf;
 	const u32 *sbuf32 = sbuf;
 	unsigned int x;
 	u32 val32;

 	for (x = 0; x < pixels; x++) {
 		val32 = ((sbuf32[x] & 0x000000FF) << 2) |
 			((sbuf32[x] & 0x0000FF00) << 4) |
 			((sbuf32[x] & 0x00FF0000) << 6);
 		*dbuf32++ = val32 | ((val32 >> 8) & 0x00300C03);
 	}
 }

 /**
  * drm_fb_xrgb8888_to_xrgb2101010_toio - Convert XRGB8888 to XRGB2101010 clip
  * buffer
  * @dst: XRGB2101010 destination buffer (iomem)
  * @dst_pitch: Number of bytes between two consecutive scanlines within dst
  * @vaddr: XRGB8888 source buffer
  * @fb: DRM framebuffer
  * @clip: Clip rectangle area to copy
  *
  * Drivers can use this function for XRGB2101010 devices that don't natively
  * support XRGB8888.
  */
 void drm_fb_xrgb8888_to_xrgb2101010_toio(void __iomem *dst,
 					 unsigned int dst_pitch, const void *vaddr,
 					 const struct drm_framebuffer *fb,
 					 const struct drm_rect *clip)
 {
 	drm_fb_xfrm_toio(dst, dst_pitch, 4, vaddr, fb, clip, false,
 			 drm_fb_xrgb8888_to_xrgb2101010_line);
 }
 EXPORT_SYMBOL(drm_fb_xrgb8888_to_xrgb2101010_toio);

 static void drm_fb_xrgb8888_to_gray8_line(void *dbuf, const void *sbuf, unsigned int pixels)
 {
 	u8 *dbuf8 = dbuf;
 	const u32 *sbuf32 = sbuf;
 	unsigned int x;

 	for (x = 0; x < pixels; x++) {
 		u8 r = (*sbuf32 & 0x00ff0000) >> 16;
 		u8 g = (*sbuf32 & 0x0000ff00) >> 8;
 		u8 b =  *sbuf32 & 0x000000ff;

 		/* ITU BT.601: Y = 0.299 R + 0.587 G + 0.114 B */
 		*dbuf8++ = (3 * r + 6 * g + b) / 10;
 		sbuf32++;
 	}
 }

 /**
  * drm_fb_xrgb8888_to_gray8 - Convert XRGB8888 to grayscale
  * @dst: 8-bit grayscale destination buffer
  * @dst_pitch: Number of bytes between two consecutive scanlines within dst
  * @vaddr: XRGB8888 source buffer
  * @fb: DRM framebuffer
  * @clip: Clip rectangle area to copy
  *
  * Drm doesn't have native monochrome or grayscale support.
  * Such drivers can announce the commonly supported XR24 format to userspace
  * and use this function to convert to the native format.
  *
  * Monochrome drivers will use the most significant bit,
  * where 1 means foreground color and 0 background color.
  *
  * ITU BT.601 is used for the RGB -> luma (brightness) conversion.
  */
 void drm_fb_xrgb8888_to_gray8(void *dst, unsigned int dst_pitch, const void *vaddr,
 			      const struct drm_framebuffer *fb, const struct drm_rect *clip)
 {
 	drm_fb_xfrm(dst, dst_pitch, 1, vaddr, fb, clip, false, drm_fb_xrgb8888_to_gray8_line);
 }
 EXPORT_SYMBOL(drm_fb_xrgb8888_to_gray8);

 /**
  * drm_fb_blit_toio - Copy parts of a framebuffer to display memory
  * @dst:	The display memory to copy to
  * @dst_pitch:	Number of bytes between two consecutive scanlines within dst
  * @dst_format:	FOURCC code of the display's color format
  * @vmap:	The framebuffer memory to copy from
  * @fb:		The framebuffer to copy from
  * @clip:	Clip rectangle area to copy
  *
  * This function copies parts of a framebuffer to display memory. If the
  * formats of the display and the framebuffer mismatch, the blit function
  * will attempt to convert between them.
  *
  * Returns:
  * 0 on success, or
  * -EINVAL if the color-format conversion failed, or
  * a negative error code otherwise.
  */
 int drm_fb_blit_toio(void __iomem *dst, unsigned int dst_pitch, uint32_t dst_format,
 		     const void *vmap, const struct drm_framebuffer *fb,
 		     const struct drm_rect *clip)
 {
 	uint32_t fb_format = fb->format->format;

 	/* treat alpha channel like filler bits */
 	if (fb_format == DRM_FORMAT_ARGB8888)
 		fb_format = DRM_FORMAT_XRGB8888;
 	if (dst_format == DRM_FORMAT_ARGB8888)
 		dst_format = DRM_FORMAT_XRGB8888;
 	if (fb_format == DRM_FORMAT_ARGB2101010)
 		fb_format = DRM_FORMAT_XRGB2101010;
 	if (dst_format == DRM_FORMAT_ARGB2101010)
 		dst_format = DRM_FORMAT_XRGB2101010;

 	if (dst_format == fb_format) {
 		drm_fb_memcpy_toio(dst, dst_pitch, vmap, fb, clip);
 		return 0;

 	} else if (dst_format == DRM_FORMAT_RGB565) {
 		if (fb_format == DRM_FORMAT_XRGB8888) {
 			drm_fb_xrgb8888_to_rgb565_toio(dst, dst_pitch, vmap, fb, clip, false);
 			return 0;
 		}
 	} else if (dst_format == DRM_FORMAT_RGB888) {
 		if (fb_format == DRM_FORMAT_XRGB8888) {
 			drm_fb_xrgb8888_to_rgb888_toio(dst, dst_pitch, vmap, fb, clip);
 			return 0;
 		}
 	} else if (dst_format == DRM_FORMAT_XRGB8888) {
 		if (fb_format == DRM_FORMAT_RGB888) {
 			drm_fb_rgb888_to_xrgb8888_toio(dst, dst_pitch, vmap, fb, clip);
 			return 0;
 		} else if (fb_format == DRM_FORMAT_RGB565) {
 			drm_fb_rgb565_to_xrgb8888_toio(dst, dst_pitch, vmap, fb, clip);
 			return 0;
 		}
 	} else if (dst_format == DRM_FORMAT_XRGB2101010) {
 		if (fb_format == DRM_FORMAT_XRGB8888) {
 			drm_fb_xrgb8888_to_xrgb2101010_toio(dst, dst_pitch, vmap, fb, clip);
 			return 0;
 		}
 	}

 	drm_warn_once(fb->dev, "No conversion helper from %p4cc to %p4cc found.\n",
 		      &fb_format, &dst_format);

 	return -EINVAL;
 }
 EXPORT_SYMBOL(drm_fb_blit_toio);


 static void drm_fb_gray8_to_mono_line(void *dbuf, const void *sbuf, unsigned int pixels)
 {
 	u8 *dbuf8 = dbuf;
 	const u8 *sbuf8 = sbuf;

 	while (pixels) {
 		unsigned int i, bits = min(pixels, 8U);
 		u8 byte = 0;

 		for (i = 0; i < bits; i++, pixels--) {
 			if (*sbuf8++ >= 128)
 				byte |= BIT(i);
 		}
 		*dbuf8++ = byte;
 	}
 }

 /**
  * drm_fb_xrgb8888_to_mono - Convert XRGB8888 to monochrome
  * @dst: monochrome destination buffer (0=black, 1=white)
  * @dst_pitch: Number of bytes between two consecutive scanlines within dst
  * @vaddr: 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 monochrome.
  *
  * The first pixel (upper left corner of the clip rectangle) will be converted
  * and copied to the first bit (LSB) in the first byte of the monochrome
  * destination buffer.
  * If the caller requires that the first pixel in a byte must be located at an
  * x-coordinate that is a multiple of 8, then the caller must take care itself
  * of supplying a suitable clip rectangle.
  */
 void drm_fb_xrgb8888_to_mono(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 = drm_rect_height(clip);
 	unsigned int cpp = fb->format->cpp[0];
 	unsigned int len_src32 = linepixels * cpp;
 	struct drm_device *dev = fb->dev;
 	unsigned int y;
 	u8 *mono = dst, *gray8;
 	u32 *src32;

 	if (drm_WARN_ON(dev, fb->format->format != DRM_FORMAT_XRGB8888))
 		return;

 	/*
 	 * The mono destination buffer contains 1 bit per pixel
 	 */
 	if (!dst_pitch)
 		dst_pitch = DIV_ROUND_UP(linepixels, 8);

 	/*
 	 * 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 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;

 	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_line(mono, gray8, linepixels);
 		vaddr += fb->pitches[0];
 		mono += dst_pitch;
 	}

 	kfree(src32);
 }
 EXPORT_SYMBOL(drm_fb_xrgb8888_to_mono);
	// SPDX-License-Identifier: GPL-2.0 or MIT
	/*
	* Copyright (C) 2016 Noralf Trønnes
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License as published by
	* the Free Software Foundation; either version 2 of the License, or
	* (at your option) any later version.
	*/

	#include <linux/module.h>
	#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)
	{
	return clip->y1 * pitch + clip->x1 * cpp;
	}

	/**
	* drm_fb_clip_offset - Returns the clipping rectangles byte-offset in a framebuffer
	* @pitch: Framebuffer line pitch in byte
	* @format: Framebuffer format
	* @clip: Clip rectangle
	*
	* Returns:
	* The byte offset of the clip rectangle's top-left corner within the framebuffer.
	*/
	unsigned int drm_fb_clip_offset(unsigned int pitch, const struct drm_format_info *format,
	const struct drm_rect *clip)
	{
	return clip_offset(clip, pitch, format->cpp[0]);
	}
	EXPORT_SYMBOL(drm_fb_clip_offset);

	/* TODO: Make this functon work with multi-plane formats. */
	static int drm_fb_xfrm(void *dst, unsigned long dst_pitch, unsigned long dst_pixsize,
	const void vaddr, const struct drm_framebuffer fb,
	const struct drm_rect *clip, bool vaddr_cached_hint,
	void (xfrm_line)(void dbuf, const void *sbuf, unsigned int npixels))
	{
	unsigned long linepixels = drm_rect_width(clip);
	unsigned long lines = drm_rect_height(clip);
	size_t sbuf_len = linepixels * fb->format->cpp[0];
	void *stmp = NULL;
	unsigned long i;
	const void *sbuf;

	/*
	* Some source buffers, such as CMA memory, use write-combine
	* caching, so reads are uncached. Speed up access by fetching
	* one line at a time.
	*/
	if (!vaddr_cached_hint) {
	stmp = kmalloc(sbuf_len, GFP_KERNEL);
	if (!stmp)
	return -ENOMEM;
	}

	if (!dst_pitch)
	dst_pitch = drm_rect_width(clip) * dst_pixsize;
	vaddr += clip_offset(clip, fb->pitches[0], fb->format->cpp[0]);

	for (i = 0; i < lines; ++i) {
	if (stmp)
	sbuf = memcpy(stmp, vaddr, sbuf_len);
	else
	sbuf = vaddr;
	xfrm_line(dst, sbuf, linepixels);
	vaddr += fb->pitches[0];
	dst += dst_pitch;
	}

	kfree(stmp);

	return 0;
	}

	/* TODO: Make this functon work with multi-plane formats. */
	static int drm_fb_xfrm_toio(void __iomem *dst, unsigned long dst_pitch, unsigned long dst_pixsize,
	const void vaddr, const struct drm_framebuffer fb,
	const struct drm_rect *clip, bool vaddr_cached_hint,
	void (xfrm_line)(void dbuf, const void *sbuf, unsigned int npixels))
	{
	unsigned long linepixels = drm_rect_width(clip);
	unsigned long lines = drm_rect_height(clip);
	size_t dbuf_len = linepixels * dst_pixsize;
	size_t stmp_off = round_up(dbuf_len, ARCH_KMALLOC_MINALIGN); /* for sbuf alignment */
	size_t sbuf_len = linepixels * fb->format->cpp[0];
	void *stmp = NULL;
	unsigned long i;
	const void *sbuf;
	void *dbuf;

	if (vaddr_cached_hint) {
	dbuf = kmalloc(dbuf_len, GFP_KERNEL);
	} else {
	dbuf = kmalloc(stmp_off + sbuf_len, GFP_KERNEL);
	stmp = dbuf + stmp_off;
	}
	if (!dbuf)
	return -ENOMEM;

	if (!dst_pitch)
	dst_pitch = linepixels * dst_pixsize;
	vaddr += clip_offset(clip, fb->pitches[0], fb->format->cpp[0]);

	for (i = 0; i < lines; ++i) {
	if (stmp)
	sbuf = memcpy(stmp, vaddr, sbuf_len);
	else
	sbuf = vaddr;
	xfrm_line(dbuf, sbuf, linepixels);
	memcpy_toio(dst, dbuf, dbuf_len);
	vaddr += fb->pitches[0];
	dst += dst_pitch;
	}

	kfree(dbuf);

	return 0;
	}

	/**
	* drm_fb_memcpy - Copy clip buffer
	* @dst: Destination buffer
	* @dst_pitch: Number of bytes between two consecutive scanlines within dst
	* @vaddr: Source buffer
	* @fb: DRM framebuffer
	* @clip: Clip rectangle area to copy
	*
	* This function does not apply clipping on dst, i.e. the destination
	* is at the top-left corner.
	*/
	void drm_fb_memcpy(void dst, unsigned int dst_pitch, const void vaddr,
	const struct drm_framebuffer fb, const struct drm_rect clip)
	{
	unsigned int cpp = fb->format->cpp[0];
	size_t len = (clip->x2 - clip->x1) * cpp;
	unsigned int y, lines = clip->y2 - clip->y1;

	if (!dst_pitch)
	dst_pitch = len;

	vaddr += clip_offset(clip, fb->pitches[0], cpp);
	for (y = 0; y < lines; y++) {
	memcpy(dst, vaddr, len);
	vaddr += fb->pitches[0];
	dst += dst_pitch;
	}
	}
	EXPORT_SYMBOL(drm_fb_memcpy);

	/**
	* drm_fb_memcpy_toio - Copy clip buffer
	* @dst: Destination buffer (iomem)
	* @dst_pitch: Number of bytes between two consecutive scanlines within dst
	* @vaddr: Source buffer
	* @fb: DRM framebuffer
	* @clip: Clip rectangle area to copy
	*
	* This function does not apply clipping on dst, i.e. the destination
	* is at the top-left corner.
	*/
	void drm_fb_memcpy_toio(void __iomem dst, unsigned int dst_pitch, const void vaddr,
	const struct drm_framebuffer fb, const struct drm_rect clip)
	{
	unsigned int cpp = fb->format->cpp[0];
	size_t len = (clip->x2 - clip->x1) * cpp;
	unsigned int y, lines = clip->y2 - clip->y1;

	if (!dst_pitch)
	dst_pitch = len;

	vaddr += clip_offset(clip, fb->pitches[0], cpp);
	for (y = 0; y < lines; y++) {
	memcpy_toio(dst, vaddr, len);
	vaddr += fb->pitches[0];
	dst += dst_pitch;
	}
	}
	EXPORT_SYMBOL(drm_fb_memcpy_toio);

	static void drm_fb_swab16_line(void dbuf, const void sbuf, unsigned int pixels)
	{
	u16 *dbuf16 = dbuf;
	const u16 *sbuf16 = sbuf;
	const u16 *send16 = sbuf16 + pixels;

	while (sbuf16 < send16)
	dbuf16++ = swab16(sbuf16++);
	}

	static void drm_fb_swab32_line(void dbuf, const void sbuf, unsigned int pixels)
	{
	u32 *dbuf32 = dbuf;
	const u32 *sbuf32 = sbuf;
	const u32 *send32 = sbuf32 + pixels;

	while (sbuf32 < send32)
	dbuf32++ = swab32(sbuf32++);
	}

	/**
	* drm_fb_swab - Swap bytes into clip buffer
	* @dst: Destination buffer
	* @dst_pitch: Number of bytes between two consecutive scanlines within dst
	* @src: Source buffer
	* @fb: DRM framebuffer
	* @clip: Clip rectangle area to copy
	* @cached: Source buffer is mapped cached (eg. not write-combined)
	*
	* If @cached is false a temporary buffer is used to cache one pixel line at a
	* time to speed up slow uncached reads.
	*
	* This function does not apply clipping on dst, i.e. the destination
	* is at the top-left corner.
	*/
	void drm_fb_swab(void dst, unsigned int dst_pitch, const void src,
	const struct drm_framebuffer fb, const struct drm_rect clip,
	bool cached)
	{
	u8 cpp = fb->format->cpp[0];

	switch (cpp) {
	case 4:
	drm_fb_xfrm(dst, dst_pitch, cpp, src, fb, clip, cached, drm_fb_swab32_line);
	break;
	case 2:
	drm_fb_xfrm(dst, dst_pitch, cpp, src, fb, clip, cached, drm_fb_swab16_line);
	break;
	default:
	drm_warn_once(fb->dev, "Format %p4cc has unsupported pixel size.\n",
	&fb->format->format);
	break;
	}
	}
	EXPORT_SYMBOL(drm_fb_swab);

	static void drm_fb_xrgb8888_to_rgb332_line(void dbuf, const void sbuf, unsigned int pixels)
	{
	u8 *dbuf8 = dbuf;
	const __le32 *sbuf32 = sbuf;
	unsigned int x;
	u32 pix;

	for (x = 0; x < pixels; x++) {
	pix = le32_to_cpu(sbuf32[x]);
	dbuf8[x] = ((pix & 0x00e00000) >> 16) \|
	((pix & 0x0000e000) >> 11) \|
	((pix & 0x000000c0) >> 6);
	}
	}

	/**
	* drm_fb_xrgb8888_to_rgb332 - Convert XRGB8888 to RGB332 clip buffer
	* @dst: RGB332 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
	*
	* Drivers can use this function for RGB332 devices that don't natively support XRGB8888.
	*/
	void drm_fb_xrgb8888_to_rgb332(void dst, unsigned int dst_pitch, const void src,
	const struct drm_framebuffer fb, const struct drm_rect clip)
	{
	drm_fb_xfrm(dst, dst_pitch, 1, src, fb, clip, false, drm_fb_xrgb8888_to_rgb332_line);
	}
	EXPORT_SYMBOL(drm_fb_xrgb8888_to_rgb332);

	static void drm_fb_xrgb8888_to_rgb565_line(void dbuf, const void sbuf, unsigned int pixels)
	{
	u16 *dbuf16 = dbuf;
	const u32 *sbuf32 = sbuf;
	unsigned int x;
	u16 val16;

	for (x = 0; x < pixels; x++) {
	val16 = ((sbuf32[x] & 0x00F80000) >> 8) \|
	((sbuf32[x] & 0x0000FC00) >> 5) \|
	((sbuf32[x] & 0x000000F8) >> 3);
	dbuf16[x] = val16;
	}
	}

	static void drm_fb_xrgb8888_to_rgb565_swab_line(void dbuf, const void sbuf,
	unsigned int pixels)
	{
	u16 *dbuf16 = dbuf;
	const u32 *sbuf32 = sbuf;
	unsigned int x;
	u16 val16;

	for (x = 0; x < pixels; x++) {
	val16 = ((sbuf32[x] & 0x00F80000) >> 8) \|
	((sbuf32[x] & 0x0000FC00) >> 5) \|
	((sbuf32[x] & 0x000000F8) >> 3);
	dbuf16[x] = swab16(val16);
	}
	}

	/**
	* drm_fb_xrgb8888_to_rgb565 - Convert XRGB8888 to RGB565 clip buffer
	* @dst: RGB565 destination buffer
	* @dst_pitch: Number of bytes between two consecutive scanlines within dst
	* @vaddr: XRGB8888 source buffer
	* @fb: DRM framebuffer
	* @clip: Clip rectangle area to copy
	* @swab: Swap bytes
	*
	* Drivers can use this function for RGB565 devices that don't natively
	* support XRGB8888.
	*/
	void drm_fb_xrgb8888_to_rgb565(void dst, unsigned int dst_pitch, const void vaddr,
	const struct drm_framebuffer fb, const struct drm_rect clip,
	bool swab)
	{
	if (swab)
	drm_fb_xfrm(dst, dst_pitch, 2, vaddr, fb, clip, false,
	drm_fb_xrgb8888_to_rgb565_swab_line);
	else
	drm_fb_xfrm(dst, dst_pitch, 2, vaddr, fb, clip, false,
	drm_fb_xrgb8888_to_rgb565_line);
	}
	EXPORT_SYMBOL(drm_fb_xrgb8888_to_rgb565);

	/**
	* drm_fb_xrgb8888_to_rgb565_toio - Convert XRGB8888 to RGB565 clip buffer
	* @dst: RGB565 destination buffer (iomem)
	* @dst_pitch: Number of bytes between two consecutive scanlines within dst
	* @vaddr: XRGB8888 source buffer
	* @fb: DRM framebuffer
	* @clip: Clip rectangle area to copy
	* @swab: Swap bytes
	*
	* Drivers can use this function for RGB565 devices that don't natively
	* support XRGB8888.
	*/
	void drm_fb_xrgb8888_to_rgb565_toio(void __iomem *dst, unsigned int dst_pitch,
	const void vaddr, const struct drm_framebuffer fb,
	const struct drm_rect *clip, bool swab)
	{
	if (swab)
	drm_fb_xfrm_toio(dst, dst_pitch, 2, vaddr, fb, clip, false,
	drm_fb_xrgb8888_to_rgb565_swab_line);
	else
	drm_fb_xfrm_toio(dst, dst_pitch, 2, vaddr, fb, clip, false,
	drm_fb_xrgb8888_to_rgb565_line);
	}
	EXPORT_SYMBOL(drm_fb_xrgb8888_to_rgb565_toio);

	static void drm_fb_xrgb8888_to_rgb888_line(void dbuf, const void sbuf, unsigned int pixels)
	{
	u8 *dbuf8 = dbuf;
	const u32 *sbuf32 = sbuf;
	unsigned int x;

	for (x = 0; x < pixels; x++) {
	*dbuf8++ = (sbuf32[x] & 0x000000FF) >> 0;
	*dbuf8++ = (sbuf32[x] & 0x0000FF00) >> 8;
	*dbuf8++ = (sbuf32[x] & 0x00FF0000) >> 16;
	}
	}

	/**
	* drm_fb_xrgb8888_to_rgb888 - Convert XRGB8888 to RGB888 clip buffer
	* @dst: RGB888 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
	*
	* Drivers can use this function for RGB888 devices that don't natively
	* support XRGB8888.
	*/
	void drm_fb_xrgb8888_to_rgb888(void dst, unsigned int dst_pitch, const void src,
	const struct drm_framebuffer fb, const struct drm_rect clip)
	{
	drm_fb_xfrm(dst, dst_pitch, 3, src, fb, clip, false, drm_fb_xrgb8888_to_rgb888_line);
	}
	EXPORT_SYMBOL(drm_fb_xrgb8888_to_rgb888);

	/**
	* drm_fb_xrgb8888_to_rgb888_toio - Convert XRGB8888 to RGB888 clip buffer
	* @dst: RGB565 destination buffer (iomem)
	* @dst_pitch: Number of bytes between two consecutive scanlines within dst
	* @vaddr: XRGB8888 source buffer
	* @fb: DRM framebuffer
	* @clip: Clip rectangle area to copy
	*
	* Drivers can use this function for RGB888 devices that don't natively
	* support XRGB8888.
	*/
	void drm_fb_xrgb8888_to_rgb888_toio(void __iomem *dst, unsigned int dst_pitch,
	const void vaddr, const struct drm_framebuffer fb,
	const struct drm_rect *clip)
	{
	drm_fb_xfrm_toio(dst, dst_pitch, 3, vaddr, fb, clip, false,
	drm_fb_xrgb8888_to_rgb888_line);
	}
	EXPORT_SYMBOL(drm_fb_xrgb8888_to_rgb888_toio);

	static void drm_fb_rgb565_to_xrgb8888_line(void dbuf, const void sbuf, unsigned int pixels)
	{
	u32 *dbuf32 = dbuf;
	const u16 *sbuf16 = sbuf;
	unsigned int x;

	for (x = 0; x < pixels; x++, ++sbuf16, ++dbuf32) {
	u32 val32 = ((*sbuf16 & 0xf800) << 8) \|
	((*sbuf16 & 0x07e0) << 5) \|
	((*sbuf16 & 0x001f) << 3);
	*dbuf32 = 0xff000000 \| val32 \|
	((val32 >> 3) & 0x00070007) \|
	((val32 >> 2) & 0x00000300);
	}
	}

	static void drm_fb_rgb565_to_xrgb8888_toio(void __iomem *dst, unsigned int dst_pitch,
	const void vaddr, const struct drm_framebuffer fb,
	const struct drm_rect *clip)
	{
	drm_fb_xfrm_toio(dst, dst_pitch, 4, vaddr, fb, clip, false,
	drm_fb_rgb565_to_xrgb8888_line);
	}

	static void drm_fb_rgb888_to_xrgb8888_line(void dbuf, const void sbuf, unsigned int pixels)
	{
	u32 *dbuf32 = dbuf;
	const u8 *sbuf8 = sbuf;
	unsigned int x;

	for (x = 0; x < pixels; x++) {
	u8 r = *sbuf8++;
	u8 g = *sbuf8++;
	u8 b = *sbuf8++;
	*dbuf32++ = 0xff000000 \| (r << 16) \| (g << 8) \| b;
	}
	}

	static void drm_fb_rgb888_to_xrgb8888_toio(void __iomem *dst, unsigned int dst_pitch,
	const void vaddr, const struct drm_framebuffer fb,
	const struct drm_rect *clip)
	{
	drm_fb_xfrm_toio(dst, dst_pitch, 4, vaddr, fb, clip, false,
	drm_fb_rgb888_to_xrgb8888_line);
	}

	static void drm_fb_xrgb8888_to_xrgb2101010_line(void dbuf, const void sbuf, unsigned int pixels)
	{
	u32 *dbuf32 = dbuf;
	const u32 *sbuf32 = sbuf;
	unsigned int x;
	u32 val32;

	for (x = 0; x < pixels; x++) {
	val32 = ((sbuf32[x] & 0x000000FF) << 2) \|
	((sbuf32[x] & 0x0000FF00) << 4) \|
	((sbuf32[x] & 0x00FF0000) << 6);
	*dbuf32++ = val32 \| ((val32 >> 8) & 0x00300C03);
	}
	}

	/**
	* drm_fb_xrgb8888_to_xrgb2101010_toio - Convert XRGB8888 to XRGB2101010 clip
	* buffer
	* @dst: XRGB2101010 destination buffer (iomem)
	* @dst_pitch: Number of bytes between two consecutive scanlines within dst
	* @vaddr: XRGB8888 source buffer
	* @fb: DRM framebuffer
	* @clip: Clip rectangle area to copy
	*
	* Drivers can use this function for XRGB2101010 devices that don't natively
	* support XRGB8888.
	*/
	void drm_fb_xrgb8888_to_xrgb2101010_toio(void __iomem *dst,
	unsigned int dst_pitch, const void *vaddr,
	const struct drm_framebuffer *fb,
	const struct drm_rect *clip)
	{
	drm_fb_xfrm_toio(dst, dst_pitch, 4, vaddr, fb, clip, false,
	drm_fb_xrgb8888_to_xrgb2101010_line);
	}
	EXPORT_SYMBOL(drm_fb_xrgb8888_to_xrgb2101010_toio);

	static void drm_fb_xrgb8888_to_gray8_line(void dbuf, const void sbuf, unsigned int pixels)
	{
	u8 *dbuf8 = dbuf;
	const u32 *sbuf32 = sbuf;
	unsigned int x;

	for (x = 0; x < pixels; x++) {
	u8 r = (*sbuf32 & 0x00ff0000) >> 16;
	u8 g = (*sbuf32 & 0x0000ff00) >> 8;
	u8 b = *sbuf32 & 0x000000ff;

	/* ITU BT.601: Y = 0.299 R + 0.587 G + 0.114 B */
	dbuf8++ = (3 r + 6 * g + b) / 10;
	sbuf32++;
	}
	}

	/**
	* drm_fb_xrgb8888_to_gray8 - Convert XRGB8888 to grayscale
	* @dst: 8-bit grayscale destination buffer
	* @dst_pitch: Number of bytes between two consecutive scanlines within dst
	* @vaddr: XRGB8888 source buffer
	* @fb: DRM framebuffer
	* @clip: Clip rectangle area to copy
	*
	* Drm doesn't have native monochrome or grayscale support.
	* Such drivers can announce the commonly supported XR24 format to userspace
	* and use this function to convert to the native format.
	*
	* Monochrome drivers will use the most significant bit,
	* where 1 means foreground color and 0 background color.
	*
	* ITU BT.601 is used for the RGB -> luma (brightness) conversion.
	*/
	void drm_fb_xrgb8888_to_gray8(void dst, unsigned int dst_pitch, const void vaddr,
	const struct drm_framebuffer fb, const struct drm_rect clip)
	{
	drm_fb_xfrm(dst, dst_pitch, 1, vaddr, fb, clip, false, drm_fb_xrgb8888_to_gray8_line);
	}
	EXPORT_SYMBOL(drm_fb_xrgb8888_to_gray8);

	/**
	* drm_fb_blit_toio - Copy parts of a framebuffer to display memory
	* @dst: The display memory to copy to
	* @dst_pitch: Number of bytes between two consecutive scanlines within dst
	* @dst_format: FOURCC code of the display's color format
	* @vmap: The framebuffer memory to copy from
	* @fb: The framebuffer to copy from
	* @clip: Clip rectangle area to copy
	*
	* This function copies parts of a framebuffer to display memory. If the
	* formats of the display and the framebuffer mismatch, the blit function
	* will attempt to convert between them.
	*
	* Returns:
	* 0 on success, or
	* -EINVAL if the color-format conversion failed, or
	* a negative error code otherwise.
	*/
	int drm_fb_blit_toio(void __iomem *dst, unsigned int dst_pitch, uint32_t dst_format,
	const void vmap, const struct drm_framebuffer fb,
	const struct drm_rect *clip)
	{
	uint32_t fb_format = fb->format->format;

	/* treat alpha channel like filler bits */
	if (fb_format == DRM_FORMAT_ARGB8888)
	fb_format = DRM_FORMAT_XRGB8888;
	if (dst_format == DRM_FORMAT_ARGB8888)
	dst_format = DRM_FORMAT_XRGB8888;
	if (fb_format == DRM_FORMAT_ARGB2101010)
	fb_format = DRM_FORMAT_XRGB2101010;
	if (dst_format == DRM_FORMAT_ARGB2101010)
	dst_format = DRM_FORMAT_XRGB2101010;

	if (dst_format == fb_format) {
	drm_fb_memcpy_toio(dst, dst_pitch, vmap, fb, clip);
	return 0;

	} else if (dst_format == DRM_FORMAT_RGB565) {
	if (fb_format == DRM_FORMAT_XRGB8888) {
	drm_fb_xrgb8888_to_rgb565_toio(dst, dst_pitch, vmap, fb, clip, false);
	return 0;
	}
	} else if (dst_format == DRM_FORMAT_RGB888) {
	if (fb_format == DRM_FORMAT_XRGB8888) {
	drm_fb_xrgb8888_to_rgb888_toio(dst, dst_pitch, vmap, fb, clip);
	return 0;
	}
	} else if (dst_format == DRM_FORMAT_XRGB8888) {
	if (fb_format == DRM_FORMAT_RGB888) {
	drm_fb_rgb888_to_xrgb8888_toio(dst, dst_pitch, vmap, fb, clip);
	return 0;
	} else if (fb_format == DRM_FORMAT_RGB565) {
	drm_fb_rgb565_to_xrgb8888_toio(dst, dst_pitch, vmap, fb, clip);
	return 0;
	}
	} else if (dst_format == DRM_FORMAT_XRGB2101010) {
	if (fb_format == DRM_FORMAT_XRGB8888) {
	drm_fb_xrgb8888_to_xrgb2101010_toio(dst, dst_pitch, vmap, fb, clip);
	return 0;
	}
	}

	drm_warn_once(fb->dev, "No conversion helper from %p4cc to %p4cc found.\n",
	&fb_format, &dst_format);

	return -EINVAL;
	}
	EXPORT_SYMBOL(drm_fb_blit_toio);


	static void drm_fb_gray8_to_mono_line(void dbuf, const void sbuf, unsigned int pixels)
	{
	u8 *dbuf8 = dbuf;
	const u8 *sbuf8 = sbuf;

	while (pixels) {
	unsigned int i, bits = min(pixels, 8U);
	u8 byte = 0;

	for (i = 0; i < bits; i++, pixels--) {
	if (*sbuf8++ >= 128)
	byte \|= BIT(i);
	}
	*dbuf8++ = byte;
	}
	}

	/**
	* drm_fb_xrgb8888_to_mono - Convert XRGB8888 to monochrome
	* @dst: monochrome destination buffer (0=black, 1=white)
	* @dst_pitch: Number of bytes between two consecutive scanlines within dst
	* @vaddr: 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 monochrome.
	*
	* The first pixel (upper left corner of the clip rectangle) will be converted
	* and copied to the first bit (LSB) in the first byte of the monochrome
	* destination buffer.
	* If the caller requires that the first pixel in a byte must be located at an
	* x-coordinate that is a multiple of 8, then the caller must take care itself
	* of supplying a suitable clip rectangle.
	*/
	void drm_fb_xrgb8888_to_mono(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 = drm_rect_height(clip);
	unsigned int cpp = fb->format->cpp[0];
	unsigned int len_src32 = linepixels * cpp;
	struct drm_device *dev = fb->dev;
	unsigned int y;
	u8 mono = dst, gray8;
	u32 *src32;

	if (drm_WARN_ON(dev, fb->format->format != DRM_FORMAT_XRGB8888))
	return;

	/*
	* The mono destination buffer contains 1 bit per pixel
	*/
	if (!dst_pitch)
	dst_pitch = DIV_ROUND_UP(linepixels, 8);

	/*
	* 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 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;

	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_line(mono, gray8, linepixels);
	vaddr += fb->pitches[0];
	mono += dst_pitch;
	}

	kfree(src32);
	}
	EXPORT_SYMBOL(drm_fb_xrgb8888_to_mono);