// SPDX-License-Identifier: GPL-2.0+

#include <linux/crc32.h>

#include <drm/drm_atomic.h>
#include <drm/drm_atomic_helper.h>
#include <drm/drm_blend.h>
#include <drm/drm_colorop.h>
#include <drm/drm_fourcc.h>
#include <drm/drm_fixed.h>
#include <drm/drm_gem_framebuffer_helper.h>
#include <drm/drm_print.h>
#include <drm/drm_vblank.h>
#include <linux/minmax.h>
#include <kunit/visibility.h>

#include "vkms_composer.h"
#include "vkms_luts.h"

static u16 pre_mul_blend_channel(u16 src, u16 dst, u16 alpha)
{
        u32 new_color;

        new_color = (src * 0xffff + dst * (0xffff - alpha));

        return DIV_ROUND_CLOSEST(new_color, 0xffff);
}

/**
 * pre_mul_alpha_blend - alpha blending equation
 * @stage_buffer: The line with the pixels from src_plane
 * @output_buffer: A line buffer that receives all the blends output
 * @x_start: The start offset
 * @pixel_count: The number of pixels to blend
 *
 * The pixels [@x_start;@x_start+@pixel_count) in stage_buffer are blended at
 * [@x_start;@x_start+@pixel_count) in output_buffer.
 *
 * The current DRM assumption is that pixel color values have been already
 * pre-multiplied with the alpha channel values. See more
 * drm_plane_create_blend_mode_property(). Also, this formula assumes a
 * completely opaque background.
 */
static void pre_mul_alpha_blend(const struct line_buffer *stage_buffer,
                                struct line_buffer *output_buffer, int x_start, int pixel_count)
{
        struct pixel_argb_u16 *out = &output_buffer->pixels[x_start];
        const struct pixel_argb_u16 *in = &stage_buffer->pixels[x_start];

        for (int i = 0; i < pixel_count; i++) {
                out[i].a = (u16)0xffff;
                out[i].r = pre_mul_blend_channel(in[i].r, out[i].r, in[i].a);
                out[i].g = pre_mul_blend_channel(in[i].g, out[i].g, in[i].a);
                out[i].b = pre_mul_blend_channel(in[i].b, out[i].b, in[i].a);
        }
}


static void fill_background(const struct pixel_argb_u16 *background_color,
                            struct line_buffer *output_buffer)
{
        for (size_t i = 0; i < output_buffer->n_pixels; i++)
                output_buffer->pixels[i] = *background_color;
}

// lerp(a, b, t) = a + (b - a) * t
VISIBLE_IF_KUNIT u16 lerp_u16(u16 a, u16 b, s64 t)
{
        s64 a_fp = drm_int2fixp(a);
        s64 b_fp = drm_int2fixp(b);

        s64 delta = drm_fixp_mul(b_fp - a_fp, t);

        return drm_fixp2int_round(a_fp + delta);
}
EXPORT_SYMBOL_IF_KUNIT(lerp_u16);

VISIBLE_IF_KUNIT s64 get_lut_index(const struct vkms_color_lut *lut, u16 channel_value)
{
        s64 color_channel_fp = drm_int2fixp(channel_value);

        return drm_fixp_mul(color_channel_fp, lut->channel_value2index_ratio);
}
EXPORT_SYMBOL_IF_KUNIT(get_lut_index);

VISIBLE_IF_KUNIT u16 apply_lut_to_channel_value(const struct vkms_color_lut *lut, u16 channel_value,
                                                enum lut_channel channel)
{
        s64 lut_index = get_lut_index(lut, channel_value);
        u16 *floor_lut_value, *ceil_lut_value;
        u16 floor_channel_value, ceil_channel_value;

        /*
         * This checks if `struct drm_color_lut` has any gap added by the compiler
         * between the struct fields.
         */
        static_assert(sizeof(struct drm_color_lut) == sizeof(__u16) * 4);

        floor_lut_value = (__u16 *)&lut->base[drm_fixp2int(lut_index)];
        if (drm_fixp2int(lut_index) == (lut->lut_length - 1))
                /* We're at the end of the LUT array, use same value for ceil and floor */
                ceil_lut_value = floor_lut_value;
        else
                ceil_lut_value = (__u16 *)&lut->base[drm_fixp2int_ceil(lut_index)];

        floor_channel_value = floor_lut_value[channel];
        ceil_channel_value = ceil_lut_value[channel];

        return lerp_u16(floor_channel_value, ceil_channel_value,
                        lut_index & DRM_FIXED_DECIMAL_MASK);
}
EXPORT_SYMBOL_IF_KUNIT(apply_lut_to_channel_value);


static void apply_lut(const struct vkms_crtc_state *crtc_state, struct line_buffer *output_buffer)
{
        if (!crtc_state->gamma_lut.base)
                return;

        if (!crtc_state->gamma_lut.lut_length)
                return;

        for (size_t x = 0; x < output_buffer->n_pixels; x++) {
                struct pixel_argb_u16 *pixel = &output_buffer->pixels[x];

                pixel->r = apply_lut_to_channel_value(&crtc_state->gamma_lut, pixel->r, LUT_RED);
                pixel->g = apply_lut_to_channel_value(&crtc_state->gamma_lut, pixel->g, LUT_GREEN);
                pixel->b = apply_lut_to_channel_value(&crtc_state->gamma_lut, pixel->b, LUT_BLUE);
        }
}

VISIBLE_IF_KUNIT void apply_3x4_matrix(struct pixel_argb_s32 *pixel,
                                       const struct drm_color_ctm_3x4 *matrix)
{
        s64 rf, gf, bf;
        s64 r, g, b;

        r = drm_int2fixp(pixel->r);
        g = drm_int2fixp(pixel->g);
        b = drm_int2fixp(pixel->b);

        rf = drm_fixp_mul(drm_sm2fixp(matrix->matrix[0]), r) +
             drm_fixp_mul(drm_sm2fixp(matrix->matrix[1]), g) +
             drm_fixp_mul(drm_sm2fixp(matrix->matrix[2]), b) +
             drm_sm2fixp(matrix->matrix[3]);

        gf = drm_fixp_mul(drm_sm2fixp(matrix->matrix[4]), r) +
             drm_fixp_mul(drm_sm2fixp(matrix->matrix[5]), g) +
             drm_fixp_mul(drm_sm2fixp(matrix->matrix[6]), b) +
             drm_sm2fixp(matrix->matrix[7]);

        bf = drm_fixp_mul(drm_sm2fixp(matrix->matrix[8]), r) +
             drm_fixp_mul(drm_sm2fixp(matrix->matrix[9]), g) +
             drm_fixp_mul(drm_sm2fixp(matrix->matrix[10]), b) +
             drm_sm2fixp(matrix->matrix[11]);

        pixel->r = drm_fixp2int_round(rf);
        pixel->g = drm_fixp2int_round(gf);
        pixel->b = drm_fixp2int_round(bf);
}
EXPORT_SYMBOL_IF_KUNIT(apply_3x4_matrix);

static void apply_colorop(struct pixel_argb_s32 *pixel, struct drm_colorop *colorop)
{
        struct drm_colorop_state *colorop_state = colorop->state;
        struct drm_device *dev = colorop->dev;

        if (colorop->type == DRM_COLOROP_1D_CURVE) {
                switch (colorop_state->curve_1d_type) {
                case DRM_COLOROP_1D_CURVE_SRGB_INV_EOTF:
                        pixel->r = apply_lut_to_channel_value(&srgb_inv_eotf, pixel->r, LUT_RED);
                        pixel->g = apply_lut_to_channel_value(&srgb_inv_eotf, pixel->g, LUT_GREEN);
                        pixel->b = apply_lut_to_channel_value(&srgb_inv_eotf, pixel->b, LUT_BLUE);
                        break;
                case DRM_COLOROP_1D_CURVE_SRGB_EOTF:
                        pixel->r = apply_lut_to_channel_value(&srgb_eotf, pixel->r, LUT_RED);
                        pixel->g = apply_lut_to_channel_value(&srgb_eotf, pixel->g, LUT_GREEN);
                        pixel->b = apply_lut_to_channel_value(&srgb_eotf, pixel->b, LUT_BLUE);
                        break;
                default:
                        drm_WARN_ONCE(dev, true,
                                      "unknown colorop 1D curve type %d\n",
                                      colorop_state->curve_1d_type);
                        break;
                }
        } else if (colorop->type == DRM_COLOROP_CTM_3X4) {
                if (colorop_state->data)
                        apply_3x4_matrix(pixel,
                                         (struct drm_color_ctm_3x4 *)colorop_state->data->data);
        }
}

static void pre_blend_color_transform(const struct vkms_plane_state *plane_state,
                                      struct line_buffer *output_buffer)
{
        struct pixel_argb_s32 pixel;

        for (size_t x = 0; x < output_buffer->n_pixels; x++) {
                struct drm_colorop *colorop = plane_state->base.base.color_pipeline;

                /*
                 * Some operations, such as applying a BT709 encoding matrix,
                 * followed by a decoding matrix, require that we preserve
                 * values above 1.0 and below 0.0 until the end of the pipeline.
                 *
                 * Pack the 16-bit UNORM values into s32 to give us head-room to
                 * avoid clipping until we're at the end of the pipeline. Clip
                 * intentionally at the end of the pipeline before packing
                 * UNORM values back into u16.
                 */
                pixel.a = output_buffer->pixels[x].a;
                pixel.r = output_buffer->pixels[x].r;
                pixel.g = output_buffer->pixels[x].g;
                pixel.b = output_buffer->pixels[x].b;

                while (colorop) {
                        struct drm_colorop_state *colorop_state;

                        colorop_state = colorop->state;

                        if (!colorop_state)
                                return;

                        if (!colorop_state->bypass)
                                apply_colorop(&pixel, colorop);

                        colorop = colorop->next;
                }

                /* clamp values */
                output_buffer->pixels[x].a = clamp_val(pixel.a, 0, 0xffff);
                output_buffer->pixels[x].r = clamp_val(pixel.r, 0, 0xffff);
                output_buffer->pixels[x].g = clamp_val(pixel.g, 0, 0xffff);
                output_buffer->pixels[x].b = clamp_val(pixel.b, 0, 0xffff);
        }
}

/**
 * direction_for_rotation() - Get the correct reading direction for a given rotation
 *
 * @rotation: Rotation to analyze. It correspond the field @frame_info.rotation.
 *
 * This function will use the @rotation setting of a source plane to compute the reading
 * direction in this plane which correspond to a "left to right writing" in the CRTC.
 * For example, if the buffer is reflected on X axis, the pixel must be read from right to left
 * to be written from left to right on the CRTC.
 */
static enum pixel_read_direction direction_for_rotation(unsigned int rotation)
{
        struct drm_rect tmp_a, tmp_b;
        int x, y;

        /*
         * Points A and B are depicted as zero-size rectangles on the CRTC.
         * The CRTC writing direction is from A to B. The plane reading direction
         * is discovered by inverse-transforming A and B.
         * The reading direction is computed by rotating the vector AB (top-left to top-right) in a
         * 1x1 square.
         */

        tmp_a = DRM_RECT_INIT(0, 0, 0, 0);
        tmp_b = DRM_RECT_INIT(1, 0, 0, 0);
        drm_rect_rotate_inv(&tmp_a, 1, 1, rotation);
        drm_rect_rotate_inv(&tmp_b, 1, 1, rotation);

        x = tmp_b.x1 - tmp_a.x1;
        y = tmp_b.y1 - tmp_a.y1;

        if (x == 1 && y == 0)
                return READ_LEFT_TO_RIGHT;
        else if (x == -1 && y == 0)
                return READ_RIGHT_TO_LEFT;
        else if (y == 1 && x == 0)
                return READ_TOP_TO_BOTTOM;
        else if (y == -1 && x == 0)
                return READ_BOTTOM_TO_TOP;

        WARN_ONCE(true, "The inverse of the rotation gives an incorrect direction.");
        return READ_LEFT_TO_RIGHT;
}

/**
 * clamp_line_coordinates() - Compute and clamp the coordinate to read and write during the blend
 * process.
 *
 * @direction: direction of the reading
 * @current_plane: current plane blended
 * @src_line: source line of the reading. Only the top-left coordinate is used. This rectangle
 * must be rotated and have a shape of 1*pixel_count if @direction is vertical and a shape of
 * pixel_count*1 if @direction is horizontal.
 * @src_x_start: x start coordinate for the line reading
 * @src_y_start: y start coordinate for the line reading
 * @dst_x_start: x coordinate to blend the read line
 * @pixel_count: number of pixels to blend
 *
 * This function is mainly a safety net to avoid reading outside the source buffer. As the
 * userspace should never ask to read outside the source plane, all the cases covered here should
 * be dead code.
 */
static void clamp_line_coordinates(enum pixel_read_direction direction,
                                   const struct vkms_plane_state *current_plane,
                                   const struct drm_rect *src_line, int *src_x_start,
                                   int *src_y_start, int *dst_x_start, int *pixel_count)
{
        /* By default the start points are correct */
        *src_x_start = src_line->x1;
        *src_y_start = src_line->y1;
        *dst_x_start = current_plane->frame_info->dst.x1;

        /* Get the correct number of pixel to blend, it depends of the direction */
        switch (direction) {
        case READ_LEFT_TO_RIGHT:
        case READ_RIGHT_TO_LEFT:
                *pixel_count = drm_rect_width(src_line);
                break;
        case READ_BOTTOM_TO_TOP:
        case READ_TOP_TO_BOTTOM:
                *pixel_count = drm_rect_height(src_line);
                break;
        }

        /*
         * Clamp the coordinates to avoid reading outside the buffer
         *
         * This is mainly a security check to avoid reading outside the buffer, the userspace
         * should never request to read outside the source buffer.
         */
        switch (direction) {
        case READ_LEFT_TO_RIGHT:
        case READ_RIGHT_TO_LEFT:
                if (*src_x_start < 0) {
                        *pixel_count += *src_x_start;
                        *dst_x_start -= *src_x_start;
                        *src_x_start = 0;
                }
                if (*src_x_start + *pixel_count > current_plane->frame_info->fb->width)
                        *pixel_count = max(0, (int)current_plane->frame_info->fb->width -
                                *src_x_start);
                break;
        case READ_BOTTOM_TO_TOP:
        case READ_TOP_TO_BOTTOM:
                if (*src_y_start < 0) {
                        *pixel_count += *src_y_start;
                        *dst_x_start -= *src_y_start;
                        *src_y_start = 0;
                }
                if (*src_y_start + *pixel_count > current_plane->frame_info->fb->height)
                        *pixel_count = max(0, (int)current_plane->frame_info->fb->height -
                                *src_y_start);
                break;
        }
}

/**
 * blend_line() - Blend a line from a plane to the output buffer
 *
 * @current_plane: current plane to work on
 * @y: line to write in the output buffer
 * @crtc_x_limit: width of the output buffer
 * @stage_buffer: temporary buffer to convert the pixel line from the source buffer
 * @output_buffer: buffer to blend the read line into.
 */
static void blend_line(struct vkms_plane_state *current_plane, int y,
                       int crtc_x_limit, struct line_buffer *stage_buffer,
                       struct line_buffer *output_buffer)
{
        int src_x_start, src_y_start, dst_x_start, pixel_count;
        struct drm_rect dst_line, tmp_src, src_line;

        /* Avoid rendering useless lines */
        if (y < current_plane->frame_info->dst.y1 ||
            y >= current_plane->frame_info->dst.y2)
                return;

        /*
         * dst_line is the line to copy. The initial coordinates are inside the
         * destination framebuffer, and then drm_rect_* helpers are used to
         * compute the correct position into the source framebuffer.
         */
        dst_line = DRM_RECT_INIT(current_plane->frame_info->dst.x1, y,
                                 drm_rect_width(&current_plane->frame_info->dst),
                                 1);

        drm_rect_fp_to_int(&tmp_src, &current_plane->frame_info->src);

        /*
         * [1]: Clamping src_line to the crtc_x_limit to avoid writing outside of
         * the destination buffer
         */
        dst_line.x1 = max_t(int, dst_line.x1, 0);
        dst_line.x2 = min_t(int, dst_line.x2, crtc_x_limit);
        /* The destination is completely outside of the crtc. */
        if (dst_line.x2 <= dst_line.x1)
                return;

        src_line = dst_line;

        /*
         * Transform the coordinate x/y from the crtc to coordinates into
         * coordinates for the src buffer.
         *
         * - Cancel the offset of the dst buffer.
         * - Invert the rotation. This assumes that
         *   dst = drm_rect_rotate(src, rotation) (dst and src have the
         *   same size, but can be rotated).
         * - Apply the offset of the source rectangle to the coordinate.
         */
        drm_rect_translate(&src_line, -current_plane->frame_info->dst.x1,
                           -current_plane->frame_info->dst.y1);
        drm_rect_rotate_inv(&src_line, drm_rect_width(&tmp_src),
                            drm_rect_height(&tmp_src),
                            current_plane->frame_info->rotation);
        drm_rect_translate(&src_line, tmp_src.x1, tmp_src.y1);

        /* Get the correct reading direction in the source buffer. */

        enum pixel_read_direction direction =
                direction_for_rotation(current_plane->frame_info->rotation);

        /* [2]: Compute and clamp the number of pixel to read */
        clamp_line_coordinates(direction, current_plane, &src_line, &src_x_start, &src_y_start,
                               &dst_x_start, &pixel_count);

        if (pixel_count <= 0) {
                /* Nothing to read, so avoid multiple function calls */
                return;
        }

        /*
         * Modify the starting point to take in account the rotation
         *
         * src_line is the top-left corner, so when reading READ_RIGHT_TO_LEFT or
         * READ_BOTTOM_TO_TOP, it must be changed to the top-right/bottom-left
         * corner.
         */
        if (direction == READ_RIGHT_TO_LEFT) {
                // src_x_start is now the right point
                src_x_start += pixel_count - 1;
        } else if (direction == READ_BOTTOM_TO_TOP) {
                // src_y_start is now the bottom point
                src_y_start += pixel_count - 1;
        }

        /*
         * Perform the conversion and the blending
         *
         * Here we know that the read line (x_start, y_start, pixel_count) is
         * inside the source buffer [2] and we don't write outside the stage
         * buffer [1].
         */
        current_plane->pixel_read_line(current_plane, src_x_start, src_y_start, direction,
                                       pixel_count, &stage_buffer->pixels[dst_x_start]);
        pre_blend_color_transform(current_plane, stage_buffer);
        pre_mul_alpha_blend(stage_buffer, output_buffer,
                            dst_x_start, pixel_count);
}

/**
 * blend - blend the pixels from all planes and compute crc
 * @wb: The writeback frame buffer metadata
 * @crtc_state: The crtc state
 * @crc32: The crc output of the final frame
 * @output_buffer: A buffer of a row that will receive the result of the blend(s)
 * @stage_buffer: The line with the pixels from plane being blend to the output
 * @row_size: The size, in bytes, of a single row
 *
 * This function blends the pixels (Using the `pre_mul_alpha_blend`)
 * from all planes, calculates the crc32 of the output from the former step,
 * and, if necessary, convert and store the output to the writeback buffer.
 */
static void blend(struct vkms_writeback_job *wb,
                  struct vkms_crtc_state *crtc_state,
                  u32 *crc32, struct line_buffer *stage_buffer,
                  struct line_buffer *output_buffer, size_t row_size)
{
        struct vkms_plane_state **plane = crtc_state->active_planes;
        u32 n_active_planes = crtc_state->num_active_planes;

        const struct pixel_argb_u16 background_color = { .a = 0xffff };

        int crtc_y_limit = crtc_state->base.mode.vdisplay;
        int crtc_x_limit = crtc_state->base.mode.hdisplay;

        /*
         * The planes are composed line-by-line to avoid heavy memory usage. It is a necessary
         * complexity to avoid poor blending performance.
         *
         * The function pixel_read_line callback is used to read a line, using an efficient
         * algorithm for a specific format, into the staging buffer.
         */
        for (int y = 0; y < crtc_y_limit; y++) {
                fill_background(&background_color, output_buffer);

                /* The active planes are composed associatively in z-order. */
                for (size_t i = 0; i < n_active_planes; i++) {
                        blend_line(plane[i], y, crtc_x_limit, stage_buffer, output_buffer);
                }

                apply_lut(crtc_state, output_buffer);

                *crc32 = crc32_le(*crc32, (void *)output_buffer->pixels, row_size);

                if (wb)
                        vkms_writeback_row(wb, output_buffer, y);
        }
}

static int check_format_funcs(struct vkms_crtc_state *crtc_state,
                              struct vkms_writeback_job *active_wb)
{
        struct vkms_plane_state **planes = crtc_state->active_planes;
        u32 n_active_planes = crtc_state->num_active_planes;

        for (size_t i = 0; i < n_active_planes; i++)
                if (!planes[i]->pixel_read_line)
                        return -1;

        if (active_wb && !active_wb->pixel_write)
                return -1;

        return 0;
}

static int check_iosys_map(struct vkms_crtc_state *crtc_state)
{
        struct vkms_plane_state **plane_state = crtc_state->active_planes;
        u32 n_active_planes = crtc_state->num_active_planes;

        for (size_t i = 0; i < n_active_planes; i++)
                if (iosys_map_is_null(&plane_state[i]->frame_info->map[0]))
                        return -1;

        return 0;
}

static int compose_active_planes(struct vkms_writeback_job *active_wb,
                                 struct vkms_crtc_state *crtc_state,
                                 u32 *crc32)
{
        size_t line_width, pixel_size = sizeof(struct pixel_argb_u16);
        struct line_buffer output_buffer, stage_buffer;
        int ret = 0;

        /*
         * This check exists so we can call `crc32_le` for the entire line
         * instead doing it for each channel of each pixel in case
         * `struct `pixel_argb_u16` had any gap added by the compiler
         * between the struct fields.
         */
        static_assert(sizeof(struct pixel_argb_u16) == 8);

        if (WARN_ON(check_iosys_map(crtc_state)))
                return -EINVAL;

        if (WARN_ON(check_format_funcs(crtc_state, active_wb)))
                return -EINVAL;

        line_width = crtc_state->base.mode.hdisplay;
        stage_buffer.n_pixels = line_width;
        output_buffer.n_pixels = line_width;

        stage_buffer.pixels = kvmalloc(line_width * pixel_size, GFP_KERNEL);
        if (!stage_buffer.pixels) {
                DRM_ERROR("Cannot allocate memory for the output line buffer");
                return -ENOMEM;
        }

        output_buffer.pixels = kvmalloc(line_width * pixel_size, GFP_KERNEL);
        if (!output_buffer.pixels) {
                DRM_ERROR("Cannot allocate memory for intermediate line buffer");
                ret = -ENOMEM;
                goto free_stage_buffer;
        }

        blend(active_wb, crtc_state, crc32, &stage_buffer,
              &output_buffer, line_width * pixel_size);

        kvfree(output_buffer.pixels);
free_stage_buffer:
        kvfree(stage_buffer.pixels);

        return ret;
}

/**
 * vkms_composer_worker - ordered work_struct to compute CRC
 *
 * @work: work_struct
 *
 * Work handler for composing and computing CRCs. work_struct scheduled in
 * an ordered workqueue that's periodically scheduled to run by
 * vkms_vblank_simulate() and flushed at vkms_atomic_commit_tail().
 */
void vkms_composer_worker(struct work_struct *work)
{
        struct vkms_crtc_state *crtc_state = container_of(work,
                                                          struct vkms_crtc_state,
                                                          composer_work);
        struct drm_crtc *crtc = crtc_state->base.crtc;
        struct vkms_writeback_job *active_wb = crtc_state->active_writeback;
        struct vkms_output *out = drm_crtc_to_vkms_output(crtc);
        bool crc_pending, wb_pending;
        u64 frame_start, frame_end;
        u32 crc32 = 0;
        int ret;

        spin_lock_irq(&out->composer_lock);
        frame_start = crtc_state->frame_start;
        frame_end = crtc_state->frame_end;
        crc_pending = crtc_state->crc_pending;
        wb_pending = crtc_state->wb_pending;
        crtc_state->frame_start = 0;
        crtc_state->frame_end = 0;
        crtc_state->crc_pending = false;

        if (crtc->state->gamma_lut) {
                s64 max_lut_index_fp;
                s64 u16_max_fp = drm_int2fixp(0xffff);

                crtc_state->gamma_lut.base = (struct drm_color_lut *)crtc->state->gamma_lut->data;
                crtc_state->gamma_lut.lut_length =
                        crtc->state->gamma_lut->length / sizeof(struct drm_color_lut);
                max_lut_index_fp = drm_int2fixp(crtc_state->gamma_lut.lut_length - 1);
                crtc_state->gamma_lut.channel_value2index_ratio = drm_fixp_div(max_lut_index_fp,
                                                                               u16_max_fp);

        } else {
                crtc_state->gamma_lut.base = NULL;
        }

        spin_unlock_irq(&out->composer_lock);

        /*
         * We raced with the vblank hrtimer and previous work already computed
         * the crc, nothing to do.
         */
        if (!crc_pending)
                return;

        if (wb_pending)
                ret = compose_active_planes(active_wb, crtc_state, &crc32);
        else
                ret = compose_active_planes(NULL, crtc_state, &crc32);

        if (ret)
                return;

        if (wb_pending) {
                drm_writeback_signal_completion(&out->wb_connector, 0);
                spin_lock_irq(&out->composer_lock);
                crtc_state->wb_pending = false;
                spin_unlock_irq(&out->composer_lock);
        }

        /*
         * The worker can fall behind the vblank hrtimer, make sure we catch up.
         */
        while (frame_start <= frame_end)
                drm_crtc_add_crc_entry(crtc, true, frame_start++, &crc32);
}

static const char *const pipe_crc_sources[] = { "auto" };

const char *const *vkms_get_crc_sources(struct drm_crtc *crtc,
                                        size_t *count)
{
        *count = ARRAY_SIZE(pipe_crc_sources);
        return pipe_crc_sources;
}

static int vkms_crc_parse_source(const char *src_name, bool *enabled)
{
        int ret = 0;

        if (!src_name) {
                *enabled = false;
        } else if (strcmp(src_name, "auto") == 0) {
                *enabled = true;
        } else {
                *enabled = false;
                ret = -EINVAL;
        }

        return ret;
}

int vkms_verify_crc_source(struct drm_crtc *crtc, const char *src_name,
                           size_t *values_cnt)
{
        bool enabled;

        if (vkms_crc_parse_source(src_name, &enabled) < 0) {
                DRM_DEBUG_DRIVER("unknown source %s\n", src_name);
                return -EINVAL;
        }

        *values_cnt = 1;

        return 0;
}

void vkms_set_composer(struct vkms_output *out, bool enabled)
{
        bool old_enabled;

        if (enabled)
                drm_crtc_vblank_get(&out->crtc);

        spin_lock_irq(&out->lock);
        old_enabled = out->composer_enabled;
        out->composer_enabled = enabled;
        spin_unlock_irq(&out->lock);

        if (old_enabled)
                drm_crtc_vblank_put(&out->crtc);
}

int vkms_set_crc_source(struct drm_crtc *crtc, const char *src_name)
{
        struct vkms_output *out = drm_crtc_to_vkms_output(crtc);
        bool enabled = false;
        int ret = 0;

        ret = vkms_crc_parse_source(src_name, &enabled);

        vkms_set_composer(out, enabled);

        return ret;
}