drivers/gpu/drm/vkms/vkms_composer.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2
   3 #include <linux/crc32.h>
   4
   5 #include <drm/drm_atomic.h>
   6 #include <drm/drm_atomic_helper.h>
   7 #include <drm/drm_blend.h>
   8 #include <drm/drm_fourcc.h>
   9 #include <drm/drm_fixed.h>
  10 #include <drm/drm_gem_framebuffer_helper.h>
  11 #include <drm/drm_vblank.h>
  12 #include <linux/minmax.h>
  13
  14 #include "vkms_drv.h"
  15
  16 static u16 pre_mul_blend_channel(u16 src, u16 dst, u16 alpha)
  17 {
  18         u32 new_color;
  19
  20         new_color = (src * 0xffff + dst * (0xffff - alpha));
  21
  22         return DIV_ROUND_CLOSEST(new_color, 0xffff);
  23 }
  24
  25 /**
  26  * pre_mul_alpha_blend - alpha blending equation
  27  * @stage_buffer: The line with the pixels from src_plane
  28  * @output_buffer: A line buffer that receives all the blends output
  29  * @x_start: The start offset
  30  * @pixel_count: The number of pixels to blend
  31  *
  32  * The pixels [@x_start;@x_start+@pixel_count) in stage_buffer are blended at
  33  * [@x_start;@x_start+@pixel_count) in output_buffer.
  34  *
  35  * The current DRM assumption is that pixel color values have been already
  36  * pre-multiplied with the alpha channel values. See more
  37  * drm_plane_create_blend_mode_property(). Also, this formula assumes a
  38  * completely opaque background.
  39  */
  40 static void pre_mul_alpha_blend(const struct line_buffer *stage_buffer,
  41                                 struct line_buffer *output_buffer, int x_start, int pixel_count)
  42 {
  43         struct pixel_argb_u16 *out = &output_buffer->pixels[x_start];
  44         const struct pixel_argb_u16 *in = &stage_buffer->pixels[x_start];
  45
  46         for (int i = 0; i < pixel_count; i++) {
  47                 out[i].a = (u16)0xffff;
  48                 out[i].r = pre_mul_blend_channel(in[i].r, out[i].r, in[i].a);
  49                 out[i].g = pre_mul_blend_channel(in[i].g, out[i].g, in[i].a);
  50                 out[i].b = pre_mul_blend_channel(in[i].b, out[i].b, in[i].a);
  51         }
  52 }
  53
  54
  55 static void fill_background(const struct pixel_argb_u16 *background_color,
  56                             struct line_buffer *output_buffer)
  57 {
  58         for (size_t i = 0; i < output_buffer->n_pixels; i++)
  59                 output_buffer->pixels[i] = *background_color;
  60 }
  61
  62 // lerp(a, b, t) = a + (b - a) * t
  63 static u16 lerp_u16(u16 a, u16 b, s64 t)
  64 {
  65         s64 a_fp = drm_int2fixp(a);
  66         s64 b_fp = drm_int2fixp(b);
  67
  68         s64 delta = drm_fixp_mul(b_fp - a_fp, t);
  69
  70         return drm_fixp2int(a_fp + delta);
  71 }
  72
  73 static s64 get_lut_index(const struct vkms_color_lut *lut, u16 channel_value)
  74 {
  75         s64 color_channel_fp = drm_int2fixp(channel_value);
  76
  77         return drm_fixp_mul(color_channel_fp, lut->channel_value2index_ratio);
  78 }
  79
  80 /*
  81  * This enum is related to the positions of the variables inside
  82  * `struct drm_color_lut`, so the order of both needs to be the same.
  83  */
  84 enum lut_channel {
  85         LUT_RED = 0,
  86         LUT_GREEN,
  87         LUT_BLUE,
  88         LUT_RESERVED
  89 };
  90
  91 static u16 apply_lut_to_channel_value(const struct vkms_color_lut *lut, u16 channel_value,
  92                                       enum lut_channel channel)
  93 {
  94         s64 lut_index = get_lut_index(lut, channel_value);
  95         u16 *floor_lut_value, *ceil_lut_value;
  96         u16 floor_channel_value, ceil_channel_value;
  97
  98         /*
  99          * This checks if `struct drm_color_lut` has any gap added by the compiler
 100          * between the struct fields.
 101          */
 102         static_assert(sizeof(struct drm_color_lut) == sizeof(__u16) * 4);
 103
 104         floor_lut_value = (__u16 *)&lut->base[drm_fixp2int(lut_index)];
 105         if (drm_fixp2int(lut_index) == (lut->lut_length - 1))
 106                 /* We're at the end of the LUT array, use same value for ceil and floor */
 107                 ceil_lut_value = floor_lut_value;
 108         else
 109                 ceil_lut_value = (__u16 *)&lut->base[drm_fixp2int_ceil(lut_index)];
 110
 111         floor_channel_value = floor_lut_value[channel];
 112         ceil_channel_value = ceil_lut_value[channel];
 113
 114         return lerp_u16(floor_channel_value, ceil_channel_value,
 115                         lut_index & DRM_FIXED_DECIMAL_MASK);
 116 }
 117
 118 static void apply_lut(const struct vkms_crtc_state *crtc_state, struct line_buffer *output_buffer)
 119 {
 120         if (!crtc_state->gamma_lut.base)
 121                 return;
 122
 123         if (!crtc_state->gamma_lut.lut_length)
 124                 return;
 125
 126         for (size_t x = 0; x < output_buffer->n_pixels; x++) {
 127                 struct pixel_argb_u16 *pixel = &output_buffer->pixels[x];
 128
 129                 pixel->r = apply_lut_to_channel_value(&crtc_state->gamma_lut, pixel->r, LUT_RED);
 130                 pixel->g = apply_lut_to_channel_value(&crtc_state->gamma_lut, pixel->g, LUT_GREEN);
 131                 pixel->b = apply_lut_to_channel_value(&crtc_state->gamma_lut, pixel->b, LUT_BLUE);
 132         }
 133 }
 134
 135 /**
 136  * direction_for_rotation() - Get the correct reading direction for a given rotation
 137  *
 138  * @rotation: Rotation to analyze. It correspond the field @frame_info.rotation.
 139  *
 140  * This function will use the @rotation setting of a source plane to compute the reading
 141  * direction in this plane which correspond to a "left to right writing" in the CRTC.
 142  * For example, if the buffer is reflected on X axis, the pixel must be read from right to left
 143  * to be written from left to right on the CRTC.
 144  */
 145 static enum pixel_read_direction direction_for_rotation(unsigned int rotation)
 146 {
 147         struct drm_rect tmp_a, tmp_b;
 148         int x, y;
 149
 150         /*
 151          * Points A and B are depicted as zero-size rectangles on the CRTC.
 152          * The CRTC writing direction is from A to B. The plane reading direction
 153          * is discovered by inverse-transforming A and B.
 154          * The reading direction is computed by rotating the vector AB (top-left to top-right) in a
 155          * 1x1 square.
 156          */
 157
 158         tmp_a = DRM_RECT_INIT(0, 0, 0, 0);
 159         tmp_b = DRM_RECT_INIT(1, 0, 0, 0);
 160         drm_rect_rotate_inv(&tmp_a, 1, 1, rotation);
 161         drm_rect_rotate_inv(&tmp_b, 1, 1, rotation);
 162
 163         x = tmp_b.x1 - tmp_a.x1;
 164         y = tmp_b.y1 - tmp_a.y1;
 165
 166         if (x == 1 && y == 0)
 167                 return READ_LEFT_TO_RIGHT;
 168         else if (x == -1 && y == 0)
 169                 return READ_RIGHT_TO_LEFT;
 170         else if (y == 1 && x == 0)
 171                 return READ_TOP_TO_BOTTOM;
 172         else if (y == -1 && x == 0)
 173                 return READ_BOTTOM_TO_TOP;
 174
 175         WARN_ONCE(true, "The inverse of the rotation gives an incorrect direction.");
 176         return READ_LEFT_TO_RIGHT;
 177 }
 178
 179 /**
 180  * clamp_line_coordinates() - Compute and clamp the coordinate to read and write during the blend
 181  * process.
 182  *
 183  * @direction: direction of the reading
 184  * @current_plane: current plane blended
 185  * @src_line: source line of the reading. Only the top-left coordinate is used. This rectangle
 186  * must be rotated and have a shape of 1*pixel_count if @direction is vertical and a shape of
 187  * pixel_count*1 if @direction is horizontal.
 188  * @src_x_start: x start coordinate for the line reading
 189  * @src_y_start: y start coordinate for the line reading
 190  * @dst_x_start: x coordinate to blend the read line
 191  * @pixel_count: number of pixels to blend
 192  *
 193  * This function is mainly a safety net to avoid reading outside the source buffer. As the
 194  * userspace should never ask to read outside the source plane, all the cases covered here should
 195  * be dead code.
 196  */
 197 static void clamp_line_coordinates(enum pixel_read_direction direction,
 198                                    const struct vkms_plane_state *current_plane,
 199                                    const struct drm_rect *src_line, int *src_x_start,
 200                                    int *src_y_start, int *dst_x_start, int *pixel_count)
 201 {
 202         /* By default the start points are correct */
 203         *src_x_start = src_line->x1;
 204         *src_y_start = src_line->y1;
 205         *dst_x_start = current_plane->frame_info->dst.x1;
 206
 207         /* Get the correct number of pixel to blend, it depends of the direction */
 208         switch (direction) {
 209         case READ_LEFT_TO_RIGHT:
 210         case READ_RIGHT_TO_LEFT:
 211                 *pixel_count = drm_rect_width(src_line);
 212                 break;
 213         case READ_BOTTOM_TO_TOP:
 214         case READ_TOP_TO_BOTTOM:
 215                 *pixel_count = drm_rect_height(src_line);
 216                 break;
 217         }
 218
 219         /*
 220          * Clamp the coordinates to avoid reading outside the buffer
 221          *
 222          * This is mainly a security check to avoid reading outside the buffer, the userspace
 223          * should never request to read outside the source buffer.
 224          */
 225         switch (direction) {
 226         case READ_LEFT_TO_RIGHT:
 227         case READ_RIGHT_TO_LEFT:
 228                 if (*src_x_start < 0) {
 229                         *pixel_count += *src_x_start;
 230                         *dst_x_start -= *src_x_start;
 231                         *src_x_start = 0;
 232                 }
 233                 if (*src_x_start + *pixel_count > current_plane->frame_info->fb->width)
 234                         *pixel_count = max(0, (int)current_plane->frame_info->fb->width -
 235                                 *src_x_start);
 236                 break;
 237         case READ_BOTTOM_TO_TOP:
 238         case READ_TOP_TO_BOTTOM:
 239                 if (*src_y_start < 0) {
 240                         *pixel_count += *src_y_start;
 241                         *dst_x_start -= *src_y_start;
 242                         *src_y_start = 0;
 243                 }
 244                 if (*src_y_start + *pixel_count > current_plane->frame_info->fb->height)
 245                         *pixel_count = max(0, (int)current_plane->frame_info->fb->height -
 246                                 *src_y_start);
 247                 break;
 248         }
 249 }
 250
 251 /**
 252  * blend_line() - Blend a line from a plane to the output buffer
 253  *
 254  * @current_plane: current plane to work on
 255  * @y: line to write in the output buffer
 256  * @crtc_x_limit: width of the output buffer
 257  * @stage_buffer: temporary buffer to convert the pixel line from the source buffer
 258  * @output_buffer: buffer to blend the read line into.
 259  */
 260 static void blend_line(struct vkms_plane_state *current_plane, int y,
 261                        int crtc_x_limit, struct line_buffer *stage_buffer,
 262                        struct line_buffer *output_buffer)
 263 {
 264         int src_x_start, src_y_start, dst_x_start, pixel_count;
 265         struct drm_rect dst_line, tmp_src, src_line;
 266
 267         /* Avoid rendering useless lines */
 268         if (y < current_plane->frame_info->dst.y1 ||
 269             y >= current_plane->frame_info->dst.y2)
 270                 return;
 271
 272         /*
 273          * dst_line is the line to copy. The initial coordinates are inside the
 274          * destination framebuffer, and then drm_rect_* helpers are used to
 275          * compute the correct position into the source framebuffer.
 276          */
 277         dst_line = DRM_RECT_INIT(current_plane->frame_info->dst.x1, y,
 278                                  drm_rect_width(&current_plane->frame_info->dst),
 279                                  1);
 280
 281         drm_rect_fp_to_int(&tmp_src, &current_plane->frame_info->src);
 282
 283         /*
 284          * [1]: Clamping src_line to the crtc_x_limit to avoid writing outside of
 285          * the destination buffer
 286          */
 287         dst_line.x1 = max_t(int, dst_line.x1, 0);
 288         dst_line.x2 = min_t(int, dst_line.x2, crtc_x_limit);
 289         /* The destination is completely outside of the crtc. */
 290         if (dst_line.x2 <= dst_line.x1)
 291                 return;
 292
 293         src_line = dst_line;
 294
 295         /*
 296          * Transform the coordinate x/y from the crtc to coordinates into
 297          * coordinates for the src buffer.
 298          *
 299          * - Cancel the offset of the dst buffer.
 300          * - Invert the rotation. This assumes that
 301          *   dst = drm_rect_rotate(src, rotation) (dst and src have the
 302          *   same size, but can be rotated).
 303          * - Apply the offset of the source rectangle to the coordinate.
 304          */
 305         drm_rect_translate(&src_line, -current_plane->frame_info->dst.x1,
 306                            -current_plane->frame_info->dst.y1);
 307         drm_rect_rotate_inv(&src_line, drm_rect_width(&tmp_src),
 308                             drm_rect_height(&tmp_src),
 309                             current_plane->frame_info->rotation);
 310         drm_rect_translate(&src_line, tmp_src.x1, tmp_src.y1);
 311
 312         /* Get the correct reading direction in the source buffer. */
 313
 314         enum pixel_read_direction direction =
 315                 direction_for_rotation(current_plane->frame_info->rotation);
 316
 317         /* [2]: Compute and clamp the number of pixel to read */
 318         clamp_line_coordinates(direction, current_plane, &src_line, &src_x_start, &src_y_start,
 319                                &dst_x_start, &pixel_count);
 320
 321         if (pixel_count <= 0) {
 322                 /* Nothing to read, so avoid multiple function calls */
 323                 return;
 324         }
 325
 326         /*
 327          * Modify the starting point to take in account the rotation
 328          *
 329          * src_line is the top-left corner, so when reading READ_RIGHT_TO_LEFT or
 330          * READ_BOTTOM_TO_TOP, it must be changed to the top-right/bottom-left
 331          * corner.
 332          */
 333         if (direction == READ_RIGHT_TO_LEFT) {
 334                 // src_x_start is now the right point
 335                 src_x_start += pixel_count - 1;
 336         } else if (direction == READ_BOTTOM_TO_TOP) {
 337                 // src_y_start is now the bottom point
 338                 src_y_start += pixel_count - 1;
 339         }
 340
 341         /*
 342          * Perform the conversion and the blending
 343          *
 344          * Here we know that the read line (x_start, y_start, pixel_count) is
 345          * inside the source buffer [2] and we don't write outside the stage
 346          * buffer [1].
 347          */
 348         current_plane->pixel_read_line(current_plane, src_x_start, src_y_start, direction,
 349                                        pixel_count, &stage_buffer->pixels[dst_x_start]);
 350
 351         pre_mul_alpha_blend(stage_buffer, output_buffer,
 352                             dst_x_start, pixel_count);
 353 }
 354
 355 /**
 356  * blend - blend the pixels from all planes and compute crc
 357  * @wb: The writeback frame buffer metadata
 358  * @crtc_state: The crtc state
 359  * @crc32: The crc output of the final frame
 360  * @output_buffer: A buffer of a row that will receive the result of the blend(s)
 361  * @stage_buffer: The line with the pixels from plane being blend to the output
 362  * @row_size: The size, in bytes, of a single row
 363  *
 364  * This function blends the pixels (Using the `pre_mul_alpha_blend`)
 365  * from all planes, calculates the crc32 of the output from the former step,
 366  * and, if necessary, convert and store the output to the writeback buffer.
 367  */
 368 static void blend(struct vkms_writeback_job *wb,
 369                   struct vkms_crtc_state *crtc_state,
 370                   u32 *crc32, struct line_buffer *stage_buffer,
 371                   struct line_buffer *output_buffer, size_t row_size)
 372 {
 373         struct vkms_plane_state **plane = crtc_state->active_planes;
 374         u32 n_active_planes = crtc_state->num_active_planes;
 375
 376         const struct pixel_argb_u16 background_color = { .a = 0xffff };
 377
 378         int crtc_y_limit = crtc_state->base.mode.vdisplay;
 379         int crtc_x_limit = crtc_state->base.mode.hdisplay;
 380
 381         /*
 382          * The planes are composed line-by-line to avoid heavy memory usage. It is a necessary
 383          * complexity to avoid poor blending performance.
 384          *
 385          * The function pixel_read_line callback is used to read a line, using an efficient
 386          * algorithm for a specific format, into the staging buffer.
 387          */
 388         for (int y = 0; y < crtc_y_limit; y++) {
 389                 fill_background(&background_color, output_buffer);
 390
 391                 /* The active planes are composed associatively in z-order. */
 392                 for (size_t i = 0; i < n_active_planes; i++) {
 393                         blend_line(plane[i], y, crtc_x_limit, stage_buffer, output_buffer);
 394                 }
 395
 396                 apply_lut(crtc_state, output_buffer);
 397
 398                 *crc32 = crc32_le(*crc32, (void *)output_buffer->pixels, row_size);
 399
 400                 if (wb)
 401                         vkms_writeback_row(wb, output_buffer, y);
 402         }
 403 }
 404
 405 static int check_format_funcs(struct vkms_crtc_state *crtc_state,
 406                               struct vkms_writeback_job *active_wb)
 407 {
 408         struct vkms_plane_state **planes = crtc_state->active_planes;
 409         u32 n_active_planes = crtc_state->num_active_planes;
 410
 411         for (size_t i = 0; i < n_active_planes; i++)
 412                 if (!planes[i]->pixel_read_line)
 413                         return -1;
 414
 415         if (active_wb && !active_wb->pixel_write)
 416                 return -1;
 417
 418         return 0;
 419 }
 420
 421 static int check_iosys_map(struct vkms_crtc_state *crtc_state)
 422 {
 423         struct vkms_plane_state **plane_state = crtc_state->active_planes;
 424         u32 n_active_planes = crtc_state->num_active_planes;
 425
 426         for (size_t i = 0; i < n_active_planes; i++)
 427                 if (iosys_map_is_null(&plane_state[i]->frame_info->map[0]))
 428                         return -1;
 429
 430         return 0;
 431 }
 432
 433 static int compose_active_planes(struct vkms_writeback_job *active_wb,
 434                                  struct vkms_crtc_state *crtc_state,
 435                                  u32 *crc32)
 436 {
 437         size_t line_width, pixel_size = sizeof(struct pixel_argb_u16);
 438         struct line_buffer output_buffer, stage_buffer;
 439         int ret = 0;
 440
 441         /*
 442          * This check exists so we can call `crc32_le` for the entire line
 443          * instead doing it for each channel of each pixel in case
 444          * `struct `pixel_argb_u16` had any gap added by the compiler
 445          * between the struct fields.
 446          */
 447         static_assert(sizeof(struct pixel_argb_u16) == 8);
 448
 449         if (WARN_ON(check_iosys_map(crtc_state)))
 450                 return -EINVAL;
 451
 452         if (WARN_ON(check_format_funcs(crtc_state, active_wb)))
 453                 return -EINVAL;
 454
 455         line_width = crtc_state->base.mode.hdisplay;
 456         stage_buffer.n_pixels = line_width;
 457         output_buffer.n_pixels = line_width;
 458
 459         stage_buffer.pixels = kvmalloc(line_width * pixel_size, GFP_KERNEL);
 460         if (!stage_buffer.pixels) {
 461                 DRM_ERROR("Cannot allocate memory for the output line buffer");
 462                 return -ENOMEM;
 463         }
 464
 465         output_buffer.pixels = kvmalloc(line_width * pixel_size, GFP_KERNEL);
 466         if (!output_buffer.pixels) {
 467                 DRM_ERROR("Cannot allocate memory for intermediate line buffer");
 468                 ret = -ENOMEM;
 469                 goto free_stage_buffer;
 470         }
 471
 472         blend(active_wb, crtc_state, crc32, &stage_buffer,
 473               &output_buffer, line_width * pixel_size);
 474
 475         kvfree(output_buffer.pixels);
 476 free_stage_buffer:
 477         kvfree(stage_buffer.pixels);
 478
 479         return ret;
 480 }
 481
 482 /**
 483  * vkms_composer_worker - ordered work_struct to compute CRC
 484  *
 485  * @work: work_struct
 486  *
 487  * Work handler for composing and computing CRCs. work_struct scheduled in
 488  * an ordered workqueue that's periodically scheduled to run by
 489  * vkms_vblank_simulate() and flushed at vkms_atomic_commit_tail().
 490  */
 491 void vkms_composer_worker(struct work_struct *work)
 492 {
 493         struct vkms_crtc_state *crtc_state = container_of(work,
 494                                                           struct vkms_crtc_state,
 495                                                           composer_work);
 496         struct drm_crtc *crtc = crtc_state->base.crtc;
 497         struct vkms_writeback_job *active_wb = crtc_state->active_writeback;
 498         struct vkms_output *out = drm_crtc_to_vkms_output(crtc);
 499         bool crc_pending, wb_pending;
 500         u64 frame_start, frame_end;
 501         u32 crc32 = 0;
 502         int ret;
 503
 504         spin_lock_irq(&out->composer_lock);
 505         frame_start = crtc_state->frame_start;
 506         frame_end = crtc_state->frame_end;
 507         crc_pending = crtc_state->crc_pending;
 508         wb_pending = crtc_state->wb_pending;
 509         crtc_state->frame_start = 0;
 510         crtc_state->frame_end = 0;
 511         crtc_state->crc_pending = false;
 512
 513         if (crtc->state->gamma_lut) {
 514                 s64 max_lut_index_fp;
 515                 s64 u16_max_fp = drm_int2fixp(0xffff);
 516
 517                 crtc_state->gamma_lut.base = (struct drm_color_lut *)crtc->state->gamma_lut->data;
 518                 crtc_state->gamma_lut.lut_length =
 519                         crtc->state->gamma_lut->length / sizeof(struct drm_color_lut);
 520                 max_lut_index_fp = drm_int2fixp(crtc_state->gamma_lut.lut_length - 1);
 521                 crtc_state->gamma_lut.channel_value2index_ratio = drm_fixp_div(max_lut_index_fp,
 522                                                                                u16_max_fp);
 523
 524         } else {
 525                 crtc_state->gamma_lut.base = NULL;
 526         }
 527
 528         spin_unlock_irq(&out->composer_lock);
 529
 530         /*
 531          * We raced with the vblank hrtimer and previous work already computed
 532          * the crc, nothing to do.
 533          */
 534         if (!crc_pending)
 535                 return;
 536
 537         if (wb_pending)
 538                 ret = compose_active_planes(active_wb, crtc_state, &crc32);
 539         else
 540                 ret = compose_active_planes(NULL, crtc_state, &crc32);
 541
 542         if (ret)
 543                 return;
 544
 545         if (wb_pending) {
 546                 drm_writeback_signal_completion(&out->wb_connector, 0);
 547                 spin_lock_irq(&out->composer_lock);
 548                 crtc_state->wb_pending = false;
 549                 spin_unlock_irq(&out->composer_lock);
 550         }
 551
 552         /*
 553          * The worker can fall behind the vblank hrtimer, make sure we catch up.
 554          */
 555         while (frame_start <= frame_end)
 556                 drm_crtc_add_crc_entry(crtc, true, frame_start++, &crc32);
 557 }
 558
 559 static const char *const pipe_crc_sources[] = { "auto" };
 560
 561 const char *const *vkms_get_crc_sources(struct drm_crtc *crtc,
 562                                         size_t *count)
 563 {
 564         *count = ARRAY_SIZE(pipe_crc_sources);
 565         return pipe_crc_sources;
 566 }
 567
 568 static int vkms_crc_parse_source(const char *src_name, bool *enabled)
 569 {
 570         int ret = 0;
 571
 572         if (!src_name) {
 573                 *enabled = false;
 574         } else if (strcmp(src_name, "auto") == 0) {
 575                 *enabled = true;
 576         } else {
 577                 *enabled = false;
 578                 ret = -EINVAL;
 579         }
 580
 581         return ret;
 582 }
 583
 584 int vkms_verify_crc_source(struct drm_crtc *crtc, const char *src_name,
 585                            size_t *values_cnt)
 586 {
 587         bool enabled;
 588
 589         if (vkms_crc_parse_source(src_name, &enabled) < 0) {
 590                 DRM_DEBUG_DRIVER("unknown source %s\n", src_name);
 591                 return -EINVAL;
 592         }
 593
 594         *values_cnt = 1;
 595
 596         return 0;
 597 }
 598
 599 void vkms_set_composer(struct vkms_output *out, bool enabled)
 600 {
 601         bool old_enabled;
 602
 603         if (enabled)
 604                 drm_crtc_vblank_get(&out->crtc);
 605
 606         spin_lock_irq(&out->lock);
 607         old_enabled = out->composer_enabled;
 608         out->composer_enabled = enabled;
 609         spin_unlock_irq(&out->lock);
 610
 611         if (old_enabled)
 612                 drm_crtc_vblank_put(&out->crtc);
 613 }
 614
 615 int vkms_set_crc_source(struct drm_crtc *crtc, const char *src_name)
 616 {
 617         struct vkms_output *out = drm_crtc_to_vkms_output(crtc);
 618         bool enabled = false;
 619         int ret = 0;
 620
 621         ret = vkms_crc_parse_source(src_name, &enabled);
 622
 623         vkms_set_composer(out, enabled);
 624
 625         return ret;
 626 }