Unverified Commit 8bde81ec authored by Marcus Folkesson's avatar Marcus Folkesson Committed by Javier Martinez Canillas
Browse files

drm/format-helper: introduce drm_fb_xrgb8888_to_gray2() 



Convert XRGB8888 to 2bit grayscale.

It uses drm_fb_xrgb8888_to_gray8() to convert the pixels to gray8 as an
intermediate step before converting to gray2.

Signed-off-by: default avatarMarcus Folkesson <marcus.folkesson@gmail.com>
Reviewed-by: default avatarJavier Martinez Canillas <javierm@redhat.com>
Acked-by: default avatarThomas Zimmermann <tzimmermann@suse.de>
Link: https://lore.kernel.org/r/20250721-st7571-format-v2-5-159f4134098c@gmail.com


Signed-off-by: default avatarJavier Martinez Canillas <javierm@redhat.com>
parent e61c3515

drivers/gpu/drm/drm_format_helper.c

+108 −0
Original line number Diff line number Diff line
@@ -1256,6 +1256,25 @@ int drm_fb_blit(struct iosys_map *dst, const unsigned int *dst_pitch, uint32_t d 
}

EXPORT_SYMBOL(drm_fb_blit);



static void drm_fb_gray8_to_gray2_line(void *dbuf, const void *sbuf, unsigned int pixels)

{

	u8 *dbuf8 = dbuf;

	const u8 *sbuf8 = sbuf;

	u8 px;



	while (pixels) {

		unsigned int i, bits = min(pixels, 4U);

		u8 byte = 0;



		for (i = 0; i < bits; i++, pixels--) {

			byte >>= 2;

			px = (*sbuf8++ * 3 + 127) / 255;

			byte |= (px &= 0x03) << 6;

		}

		*dbuf8++ = byte;

	}

}



static void drm_fb_gray8_to_mono_line(void *dbuf, const void *sbuf, unsigned int pixels)

{

	u8 *dbuf8 = dbuf;
@@ -1362,3 +1381,92 @@ void drm_fb_xrgb8888_to_mono(struct iosys_map *dst, const unsigned int *dst_pitc 
	}

}

EXPORT_SYMBOL(drm_fb_xrgb8888_to_mono);



/**

 * drm_fb_xrgb8888_to_gray2 - Convert XRGB8888 to gray2

 * @dst: Array of gray2 destination buffer

 * @dst_pitch: Array of numbers of bytes between the start of two consecutive scanlines

 *             within @dst; can be NULL if scanlines are stored next to each other.

 * @src: Array of XRGB8888 source buffers

 * @fb: DRM framebuffer

 * @clip: Clip rectangle area to copy

 * @state: Transform and conversion state

 *

 * This function copies parts of a framebuffer to display memory and converts the

 * color format during the process. Destination and framebuffer formats must match. The

 * parameters @dst, @dst_pitch and @src refer to arrays. Each array must have at

 * least as many entries as there are planes in @fb's format. Each entry stores the

 * value for the format's respective color plane at the same index.

 *

 * This function does not apply clipping on @dst (i.e. the destination is at the

 * top-left corner). The first pixel (upper left corner of the clip rectangle) will

 * be converted and copied to the two first bits (LSB) in the first byte of the gray2

 * 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.

 *

 * DRM doesn't have native gray2 support. Drivers can use this function for

 * gray2 devices that don't support XRGB8888 natively. Such drivers can

 * announce the commonly supported XR24 format to userspace and use this function

 * to convert to the native format.

 *

 */

void drm_fb_xrgb8888_to_gray2(struct iosys_map *dst, const unsigned int *dst_pitch,

			      const struct iosys_map *src, const struct drm_framebuffer *fb,

			      const struct drm_rect *clip, struct drm_format_conv_state *state)

{

	static const unsigned int default_dst_pitch[DRM_FORMAT_MAX_PLANES] = {

		0, 0, 0, 0

	};

	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;

	void *vaddr = src[0].vaddr;

	unsigned int dst_pitch_0;

	unsigned int y;

	u8 *gray2 = dst[0].vaddr, *gray8;

	u32 *src32;



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

		return;



	if (!dst_pitch)

		dst_pitch = default_dst_pitch;

	dst_pitch_0 = dst_pitch[0];



	/*

	 * The gray2 destination buffer contains 2 bit per pixel

	 */

	if (!dst_pitch_0)

		dst_pitch_0 = DIV_ROUND_UP(linepixels, 4);



	/*

	 * The dma memory is write-combined so reads are uncached.

	 * Speed up by fetching one line at a time.

	 *

	 * Also, format conversion from XR24 to gray2 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 = drm_format_conv_state_reserve(state, 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_gray2_line(gray2, gray8, linepixels);

		vaddr += fb->pitches[0];

		gray2 += dst_pitch_0;

	}

}

EXPORT_SYMBOL(drm_fb_xrgb8888_to_gray2);

include/drm/drm_format_helper.h

+4 −0
Original line number Diff line number Diff line
@@ -136,4 +136,8 @@ void drm_fb_xrgb8888_to_mono(struct iosys_map *dst, const unsigned int *dst_pitc 
			     const struct iosys_map *src, const struct drm_framebuffer *fb,

			     const struct drm_rect *clip, struct drm_format_conv_state *state);



void drm_fb_xrgb8888_to_gray2(struct iosys_map *dst, const unsigned int *dst_pitch,

			      const struct iosys_map *src, const struct drm_framebuffer *fb,

			      const struct drm_rect *clip, struct drm_format_conv_state *state);



#endif /* __LINUX_DRM_FORMAT_HELPER_H */