xref: /haiku/src/add-ons/accelerants/matrox/Overlay.c (revision 93a78ecaa45114d68952d08c4778f073515102f2)
1 /* Written by Rudolf Cornelissen 05-2002/4-2006 */
2 
3 /* Note on 'missing features' in BeOS 5.0.3 and DANO:
4  * BeOS needs to define more colorspaces! It would be nice if BeOS would support the FourCC 'definitions'
5  * of colorspaces. These colorspaces are 32bit words, so it could be simply done (or is it already so?)
6  */
7 
8 #define MODULE_BIT 0x00000400
9 
10 #include "acc_std.h"
11 
12 /* define the supported overlay input colorspaces */
13 /* Note:
14  * G200-G550 can all do YUV4:2:0 2-plane colorspace as well,
15  * G200 does not support RGB modes while > G200 do (but with limited scaling and without filtering),
16  * G200 does not support YUV4:2:0 3-plane mode while > G200 do.
17  * It would be nice to have the YUV4:2:0 2-plane mode implemented also later on, but the Be colorspace
18  * definitions (in GraphicsDefs.h, R5.0.3 and DANO5.1d0) do not include this one... */
19 static uint32 overlay_colorspaces [] = { (uint32)B_YCbCr422, (uint32)B_NO_COLOR_SPACE };
20 
21 uint32 OVERLAY_COUNT(const display_mode *dm)
22 // This method is never used AFAIK though it *is* exported on R5.0.3 and DANO.
23 // Does someone know howto invoke it?
24 {
25 	LOG(4,("Overlay: count called\n"));
26 
27 	/* check for NULL pointer */
28 	if (dm == NULL)
29 	{
30 		LOG(4,("Overlay: No display mode specified!\n"));
31 	}
32 	/* apparantly overlay count should report the number of 'overlay units' on the card */
33 	return 1;
34 }
35 
36 const uint32 *OVERLAY_SUPPORTED_SPACES(const display_mode *dm)
37 // This method is never used AFAIK though it *is* exported on R5.0.3 and DANO.
38 // Does someone know howto invoke it?
39 {
40 	LOG(4,("Overlay: supported_spaces called.\n"));
41 
42 	/* check for NULL pointer */
43 	if (dm == NULL)
44 	{
45 		LOG(4,("Overlay: No display mode specified!\n"));
46 		return NULL;
47 	}
48 
49 	/* interlaced VGA is not supported by G200-G550 BES */
50 	if (dm->timing.flags & B_TIMING_INTERLACED)
51 	{
52 		return NULL;
53 	}
54 	/* return a B_NO_COLOR_SPACE terminated list */
55 	return &overlay_colorspaces[0];
56 }
57 
58 uint32 OVERLAY_SUPPORTED_FEATURES(uint32 a_color_space)
59 // This method is never used AFAIK. On R5.0.3 and DANO it is not even exported!
60 {
61 	LOG(4,("Overlay: supported_features: color_space $%08x\n",a_color_space));
62 
63 	/* check what features (like the keying method) are supported on the current
64 	 * Desktop colorspace */
65 	//fixme? Or are we talking about the overlay input bitmap's colorspace?
66 	switch (a_color_space)
67 	{
68 	default:
69 			/* fixme: for now 'direct 32bit' desktop colorspace assumed */
70 			return
71 				( B_OVERLAY_KEYING_USES_ALPHA 	 |
72 				  B_OVERLAY_COLOR_KEY 			 |
73 				  B_OVERLAY_HORIZONTAL_FILTERING |
74 				  B_OVERLAY_VERTICAL_FILTERING );
75 	}
76 }
77 
78 const overlay_buffer *ALLOCATE_OVERLAY_BUFFER(color_space cs, uint16 width, uint16 height)
79 {
80 	int offset = 0;					/* used to determine next buffer to create */
81 	uint32 adress, adress2, temp32;	/* used to calculate buffer adresses */
82 	uint32 oldsize = 0;				/* used to 'squeeze' new buffers between already existing ones */
83 	int cnt;						/* loopcounter */
84 
85 	/* acquire the shared benaphore */
86 	AQUIRE_BEN(si->overlay.lock)
87 
88 	LOG(4,("Overlay: cardRAM_start = $%08x\n",(uint32)((uint8*)si->framebuffer)));
89 	LOG(4,("Overlay: cardRAM_start_DMA = $%08x\n",(uint32)((uint8*)si->framebuffer_pci)));
90 	LOG(4,("Overlay: cardRAM_size = %dMb\n",si->ps.memory_size));
91 
92 	/* find first empty slot (room for another buffer?) */
93 	for (offset = 0; offset < MAXBUFFERS; offset++)
94 	{
95 		if (si->overlay.myBuffer[offset].buffer == NULL) break;
96 	}
97 
98 	LOG(4,("Overlay: Allocate_buffer offset = %d\n",offset));
99 
100 	if (offset < MAXBUFFERS)
101 	/* setup new scaler input buffer */
102 	{
103 		switch (cs)
104 		{
105 			case B_YCbCr422:
106 					/* check if slopspace is needed: compatible settings choosen for now:
107 					 * G200 can do with ~0x0003 while > G200 need ~x0007.
108 					 * Optimized settings for G200 could reduce CPU load a tiny little bit there... */
109 					/* fixme: update needed for DVDmax support to adhere to CRTC2 constraints:
110 					 * case display_mode == B_RGB16: multiple = 32
111 					 * case display_mode == B_RGB32: multiple = 16 */
112 					if (width == (width & ~0x0007))
113 					{
114 						si->overlay.myBuffer[offset].width = width;
115 					}
116 					else
117 					{
118 						si->overlay.myBuffer[offset].width = (width & ~0x0007) + 8;
119 					}
120 					si->overlay.myBuffer[offset].bytes_per_row = 2 * si->overlay.myBuffer[offset].width;
121 
122 					/* check if the requested horizontal pitch is supported:
123 					 * G200 max. pitch is 4092 pixels, > G200 max pitch is 4088 pixels for this colorspace.
124 					 * Compatible check done, has no downside consequences here. */
125 					if (si->overlay.myBuffer[offset].width > 4088)
126 					{
127 						LOG(4,("Overlay: Sorry, requested buffer pitch not supported, aborted\n"));
128 
129 						/* release the shared benaphore */
130 						RELEASE_BEN(si->overlay.lock)
131 
132 						return NULL;
133 					}
134 					break;
135 
136 //			case 0xffff://fixme: which one(s)?
137 					//fixme: 4:2:0 2-plane supported format, should be selected only if detected
138 					/* check if slopspace is needed: compatible settings choosen for now:
139 					 * G200 can do with ~0x0007 while > G200 need ~x001f.
140 					 * Optimized settings for G200 could reduce CPU load a tiny little bit there... */
141 /*					if (width == (width & ~0x001f))
142 					{
143 						si->overlay.myBuffer[offset].width = width;
144 					}
145 					else
146 					{
147 						si->overlay.myBuffer[offset].width = (width & ~0x001f) + 32;
148 					}
149 */					/* assuming Y-plane only bytes_per_row are requested here */
150 /*					si->overlay.myBuffer[offset].bytes_per_row = si->overlay.myBuffer[offset].width;
151 */
152 					/* check if the requested horizontal pitch is supported:
153 					 * G200 max. pitch is 4088 pixels, > G200 max pitch is 4064 pixels for this colorspace.
154 					 * Compatible check done, has no real downside consequences here. */
155 /*					if (si->overlay.myBuffer[offset].width > 4064)
156 					{
157 						LOG(4,("Overlay: Sorry, requested buffer pitch not supported, aborted\n");
158 */
159 						/* release the shared benaphore */
160 /*						RELEASE_BEN(si->overlay.lock)
161 
162 						return NULL;
163 					}
164 					break;
165 */
166 			default:
167 					/* unsupported colorspace! */
168 					LOG(4,("Overlay: Sorry, colorspace $%08x not supported, aborted\n",cs));
169 
170 					/* release the shared benaphore */
171 					RELEASE_BEN(si->overlay.lock)
172 
173 					return NULL;
174 					break;
175 		}
176 
177 		/* check if the requested buffer width is supported */
178 		if (si->overlay.myBuffer[offset].width > 1024)
179 		{
180 			LOG(4,("Overlay: Sorry, requested buffer width not supported, aborted\n"));
181 
182 			/* release the shared benaphore */
183 			RELEASE_BEN(si->overlay.lock)
184 
185 			return NULL;
186 		}
187 		/* check if the requested buffer height is supported */
188 		if (height > 1024)
189 		{
190 			LOG(4,("Overlay: Sorry, requested buffer height not supported, aborted\n"));
191 
192 			/* release the shared benaphore */
193 			RELEASE_BEN(si->overlay.lock)
194 
195 			return NULL;
196 		}
197 
198 		/* store slopspace (in pixels) for each bitmap for use by 'overlay unit' (BES) */
199 		si->overlay.myBufInfo[offset].slopspace = si->overlay.myBuffer[offset].width - width;
200 
201 		si->overlay.myBuffer[offset].space = cs;
202 		si->overlay.myBuffer[offset].height = height;
203 
204 		/* we define the overlay buffers to reside 'in the back' of the cards RAM */
205 		/* NOTE to app programmers:
206 		 * Beware that an app using overlay needs to track workspace switches and screenprefs
207 		 * changes. If such an action is detected, the app needs to reset it's pointers to the
208 		 * newly created overlay bitmaps, which will be assigned by BeOS automatically after such
209 		 * an event. (Also the app needs to respect the new overlay_constraints that will be applicable!)
210 		 *
211 		 * It is entirely possible that new bitmaps may *not* be re-setup at all, or less of them
212 		 * than previously setup by the app might be re-setup. This is due to cardRAM restraints then.
213 		 * This means that the app should also check for NULL pointers returned by the bitmaps,
214 		 * and if this happens, it needs to fallback to single buffered overlay or even fallback to
215 		 * bitmap output for the new situation. */
216 
217 		/* Another NOTE for app programmers:
218 		 * A *positive* side-effect of assigning the first overlay buffer exactly at the end of the
219 		 * cardRAM is that apps that try to write beyond the buffer's space get a segfault immediately.
220 		 * This *greatly* simplifies tracking such errors!
221 		 * Of course such errors may lead to strange effects in the app or driver behaviour if they are
222 		 * not hunted down and removed.. */
223 
224 		/* calculate first free RAM adress in card:
225 		 * Driver setup is as follows:
226 		 * card base: 		- hardware cursor bitmap (if used),
227 		 * directly above	- screen memory for both heads */
228 		adress2 = (((uint32)((uint8*)si->fbc.frame_buffer)) +	/* cursor already included here */
229 			(si->fbc.bytes_per_row * si->dm.virtual_height));	/* size in bytes of screen(s) */
230 		LOG(4,("Overlay: first free cardRAM virtual adress $%08x\n", adress2));
231 
232 		/* calculate 'preliminary' buffer size including slopspace */
233 		oldsize = si->overlay.myBufInfo[offset].size;
234 		si->overlay.myBufInfo[offset].size =
235 			si->overlay.myBuffer[offset].bytes_per_row * si->overlay.myBuffer[offset].height;
236 
237 		/* calculate virtual memory adress that would be needed for a new bitmap */
238 		/* NOTE to app programmers:
239 		 * For testing app behaviour regarding workspace switches or screen prefs changes to settings
240 		 * that do not have enough cardRAM left for allocation of overlay bitmaps, you need a card with
241 		 * a low amount of RAM. Or you can set in the file matrox.settings for example:
242 		 * memory 8 #8Mb RAM on card
243 		 * and reboot (this simulates 8Mb RAM on the card).
244 		 *
245 		 * If you switch now to settings: 1600x1200x32bit (single head) the app needs to fallback to
246 		 * bitmap output or maybe single buffered overlay output if small bitmaps are used. */
247 
248 		adress = (((uint32)((uint8*)si->framebuffer)) + (si->ps.memory_size * 1024 * 1024));
249 		for (cnt = 0; cnt <= offset; cnt++)
250 		{
251 			adress -= si->overlay.myBufInfo[cnt].size;
252 		}
253 
254 		/* the > G200 scalers require buffers to be aligned to 16 byte pages cardRAM offset, G200 can do with
255 		 * 8 byte pages cardRAM offset. Compatible settings used, has no real downside consequences here */
256 
257 		/* Check if we need to modify the buffers starting adress and thus the size */
258 		/* calculate 'would be' cardRAM offset */
259 		temp32 = (adress - ((uint32)((vuint32 *)si->framebuffer)));
260 		/* check if it is aligned */
261 		if (temp32 != (temp32 & 0xfffffff0))
262 		{
263 			/* update the (already calculated) buffersize to get it aligned */
264 			si->overlay.myBufInfo[offset].size += (temp32 - (temp32 & 0xfffffff0));
265 			/* update the (already calculated) adress to get it aligned */
266 			adress -= (temp32 - (temp32 & 0xfffffff0));
267 		}
268 		LOG(4,("Overlay: new buffer needs virtual adress $%08x\n", adress));
269 
270 		/* First check now if buffer to be defined is 'last one' in memory (speaking backwards):
271 		 * this is done to prevent a large buffer getting created in the space a small buffer
272 		 * occupied earlier, if not all buffers created were deleted.
273 		 * Note also that the app can delete the buffers in any order desired. */
274 
275 		/* NOTE to app programmers:
276 		 * If you are going to delete a overlay buffer you created, you should delete them *all* and
277 		 * then re-create only the new ones needed. This way you are sure not to get unused memory-
278 		 * space in between your overlay buffers for instance, so cardRAM is used 'to the max'.
279 		 * If you don't, you might not get a buffer at all if you are trying to set up a larger one
280 		 * than before.
281 		 * (Indeed: not all buffers *have* to be of the same type and size...) */
282 
283 		for (cnt = offset; cnt < MAXBUFFERS; cnt++)
284 		{
285 			if (si->overlay.myBuffer[cnt].buffer != NULL)
286 			{
287 				/* Check if the new buffer would fit into the space the single old one used here */
288 				if (si->overlay.myBufInfo[offset].size <= oldsize)
289 				{
290 					/* It does, so we reset to the old size and adresses to prevent the space from shrinking
291 					 * if we get here again... */
292 					adress -= (oldsize - si->overlay.myBufInfo[offset].size);
293 					si->overlay.myBufInfo[offset].size = oldsize;
294 					LOG(4,("Overlay: 'squeezing' in buffer:\n"
295 						   "Overlay: resetting it to virtual adress $%08x and size $%08x\n", adress,oldsize));
296 					/* force exiting the FOR loop */
297 					cnt = MAXBUFFERS;
298 				}
299 				else
300 				{
301 					/* nogo, sorry */
302 					LOG(4,("Overlay: Other buffer(s) exist after this one:\n"
303 						   "Overlay: not enough space to 'squeeze' this one in, aborted\n"));
304 
305 					/* Reset to the old size to prevent the space from 'growing' if we get here again... */
306 					si->overlay.myBufInfo[offset].size = oldsize;
307 
308 					/* release the shared benaphore */
309 					RELEASE_BEN(si->overlay.lock)
310 
311 					return NULL;
312 				}
313 			}
314 		}
315 
316 		/* check if we have enough space to setup this new bitmap
317 		 * (preventing overlap of desktop RAMspace & overlay bitmap RAMspace here) */
318 		if (adress < adress2)
319 		/* nope, sorry */
320 		{
321 			LOG(4,("Overlay: Sorry, no more space for buffers: aborted\n"));
322 
323 			/* release the shared benaphore */
324 			RELEASE_BEN(si->overlay.lock)
325 
326 			return NULL;
327 		}
328 		/* continue buffer setup */
329 		si->overlay.myBuffer[offset].buffer = (void *) adress;
330 
331 		/* calculate physical memory adress (for dma use) */
332 		/* NOTE to app programmers:
333 		 * For testing app behaviour regarding workspace switches or screen prefs changes to settings
334 		 * that do not have enough cardRAM left for allocation of overlay bitmaps, you need a card with
335 		 * a low amount of RAM. Or you can set in the file matrox.settings for example:
336 		 * memory 8 #8Mb RAM on card
337 		 * and reboot (this simulates 8Mb RAM on the card).
338 		 *
339 		 * If you switch now to settings: 1600x1200x32bit (single head) the app needs to fallback to
340 		 * bitmap output or maybe single buffered overlay output if small bitmaps are used. */
341 
342 		adress = (((uint32)((uint8*)si->framebuffer_pci)) + (si->ps.memory_size * 1024 * 1024));
343 		for (cnt = 0; cnt <= offset; cnt++)
344 		{
345 			adress -= si->overlay.myBufInfo[cnt].size;
346 		}
347 		/* this adress is already aligned to the scaler's requirements (via the already modified sizes) */
348 		si->overlay.myBuffer[offset].buffer_dma = (void *) adress;
349 
350 		LOG(4,("Overlay: New buffer: addr $%08x, dma_addr $%08x, color space $%08x\n",
351 			(uint32)((uint8*)si->overlay.myBuffer[offset].buffer),
352 			(uint32)((uint8*)si->overlay.myBuffer[offset].buffer_dma), cs));
353 		LOG(4,("Overlay: New buffer's size is $%08x\n", si->overlay.myBufInfo[offset].size));
354 
355 		/* release the shared benaphore */
356 		RELEASE_BEN(si->overlay.lock)
357 
358 		return &si->overlay.myBuffer[offset];
359 	}
360 	else
361 	/* sorry, no more room for buffers */
362 	{
363 		LOG(4,("Overlay: Sorry, no more space for buffers: aborted\n"));
364 
365 		/* release the shared benaphore */
366 		RELEASE_BEN(si->overlay.lock)
367 
368 		return NULL;
369 	}
370 }
371 
372 status_t RELEASE_OVERLAY_BUFFER(const overlay_buffer *ob)
373 /* Note that the user can delete the buffers in any order desired! */
374 {
375 	int offset = 0;
376 
377 	if (ob != NULL)
378 	{
379 		/* find the buffer */
380 		for (offset = 0; offset < MAXBUFFERS; offset++)
381 		{
382 			if (si->overlay.myBuffer[offset].buffer == ob->buffer) break;
383 		}
384 
385 		if (offset < MAXBUFFERS)
386 		/* delete current buffer */
387 		{
388 			si->overlay.myBuffer[offset].buffer = NULL;
389 			si->overlay.myBuffer[offset].buffer_dma = NULL;
390 
391 			LOG(4,("Overlay: Release_buffer offset = %d, buffer released\n",offset));
392 
393 			return B_OK;
394 		}
395 		else
396 		{
397 			/* this is no buffer of ours! */
398 			LOG(4,("Overlay: Release_overlay_buffer: not ours, aborted!\n"));
399 
400 			return B_ERROR;
401 		}
402 	}
403 	else
404 	/* no buffer specified! */
405 	{
406 		LOG(4,("Overlay: Release_overlay_buffer: no buffer specified, aborted!\n"));
407 
408 		return B_ERROR;
409 	}
410 }
411 
412 status_t GET_OVERLAY_CONSTRAINTS
413 	(const display_mode *dm, const overlay_buffer *ob, overlay_constraints *oc)
414 {
415 	int offset = 0;
416 
417 	LOG(4,("Overlay: Get_overlay_constraints called\n"));
418 
419 	/* check for NULL pointers */
420 	if ((dm == NULL) || (ob == NULL) || (oc == NULL))
421 	{
422 		LOG(4,("Overlay: Get_overlay_constraints: Null pointer(s) detected!\n"));
423 		return B_ERROR;
424 	}
425 
426 	/* find the buffer */
427 	for (offset = 0; offset < MAXBUFFERS; offset++)
428 	{
429 		if (si->overlay.myBuffer[offset].buffer == ob->buffer) break;
430 	}
431 
432 	if (offset < MAXBUFFERS)
433 	{
434 		/* scaler input (values are in pixels) */
435 		oc->view.h_alignment = 0;
436 		oc->view.v_alignment = 0;
437 
438 		switch (ob->space)
439 		{
440 			case B_YCbCr422:
441 					/* G200 can work with 3, > G200 need 7. Compatible setting returned for now.
442 					 * Note: this has to be in sync with the slopspace setup during buffer allocation.. */
443 					oc->view.width_alignment = 7;
444 					break;
445 
446 //			case 0xffff://fixme: which one(s)? (4:2:0 supported formats. Not yet used...)
447 					/* G200 can work with 7, > G200 need 31. Compatible setting returned for now.
448 					 * Note: this has to be in sync with the slopspace setup during buffer allocation.. */
449 /*					oc->view.width_alignment = 31;
450 					break;
451 */
452 			default:
453 					/* we should not be here, but set the worst-case value just to be safe anyway */
454 					oc->view.width_alignment = 31;
455 					break;
456 		}
457 
458 		oc->view.height_alignment = 0;
459 		oc->view.width.min = 1;
460 		oc->view.height.min = 2; /* two fields */
461 		oc->view.width.max = ob->width;
462 		oc->view.height.max = ob->height;
463 
464 		/* scaler output restrictions */
465 		oc->window.h_alignment = 0;
466 		oc->window.v_alignment = 0;
467 		oc->window.width_alignment = 0;
468 		oc->window.height_alignment = 0;
469 		oc->window.width.min = 2;
470 		/* G200-G550 can output upto and including 2048 pixels in width */
471 		if (dm->virtual_width > 2048)
472 		{
473 			oc->window.width.max = 2048;
474 		}
475 		else
476 		{
477 			oc->window.width.max = dm->virtual_width;
478 		}
479 		oc->window.height.min = 2;
480 		/* G200-G550 can output upto and including 2048 pixels in height */
481 		if (dm->virtual_height > 2048)
482 		{
483 			oc->window.height.max = 2048;
484 		}
485 		else
486 		{
487 			oc->window.height.max = dm->virtual_height;
488 		}
489 
490 		/* G200-G550 scaling restrictions */
491 		/* Adjust horizontal restrictions if pixelclock is above BES max. speed! */
492 		/* Note: If RGB32 is implemented no scaling is supported! */
493 		if (si->dm.timing.pixel_clock > BESMAXSPEED)
494 		{
495 			oc->h_scale.min = (1 * 2) / (32 - (1 / (float)16384));
496 			oc->h_scale.max = (16384 * 2)/(float)(ob->width - si->overlay.myBufInfo[offset].slopspace);
497 		}
498 		else
499 		{
500 			oc->h_scale.min = 1 / (32 - (1 / (float)16384));
501 			oc->h_scale.max = 16384/(float)(ob->width - si->overlay.myBufInfo[offset].slopspace);
502 		}
503 		oc->v_scale.min = 1 / (32 - (1 / (float)16384));
504 		oc->v_scale.max = 16384/(float)ob->height;
505 
506 		return B_OK;
507 	}
508 	else
509 	{
510 		/* this is no buffer of ours! */
511 		LOG(4,("Overlay: Get_overlay_constraints: buffer is not ours, aborted!\n"));
512 
513 		return B_ERROR;
514 	}
515 }
516 
517 overlay_token ALLOCATE_OVERLAY(void)
518 {
519 	uint32 tmpToken;
520 	LOG(4,("Overlay: Allocate_overlay called: "));
521 
522 	/* come up with a token */
523 	tmpToken = 0x12345678;
524 
525 	/* acquire the shared benaphore */
526 	AQUIRE_BEN(si->overlay.lock)
527 
528 	/* overlay unit already in use? */
529 	if (si->overlay.myToken == NULL)
530 	/* overlay unit is available */
531 	{
532 		LOG(4,("succesfull\n"));
533 
534 		si->overlay.myToken = &tmpToken;
535 
536 		/* release the shared benaphore */
537 		RELEASE_BEN(si->overlay.lock)
538 
539 		return si->overlay.myToken;
540 	}
541 	else
542 	/* sorry, overlay unit is occupied */
543 	{
544 		LOG(4,("failed: already in use!\n"));
545 
546 		/* release the shared benaphore */
547 		RELEASE_BEN(si->overlay.lock)
548 
549 		return NULL;
550 	}
551 }
552 
553 status_t RELEASE_OVERLAY(overlay_token ot)
554 {
555 	LOG(4,("Overlay: Release_overlay called: "));
556 
557 	/* is this call for real? */
558 	if ((ot == NULL) || (si->overlay.myToken == NULL) || (ot != si->overlay.myToken))
559 	/* nope, abort */
560 	{
561 		LOG(4,("failed, not in use!\n"));
562 
563 		return B_ERROR;
564 	}
565 	else
566 	/* call is for real */
567 	{
568 
569 		gx00_release_bes();
570 
571 		LOG(4,("succesfull\n"));
572 
573 		si->overlay.myToken = NULL;
574 		return B_OK;
575 	}
576 }
577 
578 status_t CONFIGURE_OVERLAY
579 	(overlay_token ot, const overlay_buffer *ob, const overlay_window *ow, const overlay_view *ov)
580 {
581 	int offset = 0; /* used for buffer index */
582 
583 	LOG(4,("Overlay: Configure_overlay called: "));
584 
585 	/* Note:
586 	 * When a Workspace switch, screen prefs change, or overlay app shutdown occurs, BeOS will
587 	 * release all overlay buffers. The buffer currently displayed at that moment, may need some
588 	 * 'hardware releasing' in the CONFIGURE_OVERLAY routine. This is why CONFIGURE_OVERLAY gets
589 	 * called one more time then, with a null pointer for overlay_window and overlay_view, while
590 	 * the currently displayed overlay_buffer is given.
591 	 * The G200-G550 do not need to do anything on such an occasion, so we simply return if we
592 	 * get called then. */
593 	if ((ow == NULL) || (ov == NULL))
594 	{
595 		LOG(4,("output properties changed\n"));
596 
597 		return B_OK;
598 	}
599 
600 	/* Note:
601 	 * If during overlay use the screen prefs are changed, or the workspace has changed, it
602 	 * may be that we were not able to re-allocate the requested overlay buffers (or only partly)
603 	 * due to lack of cardRAM. If the app does not respond properly to this, we might end up
604 	 * with a NULL pointer instead of a overlay_buffer to work with here.
605 	 * Of course, we need to abort then to prevent the system from 'going down'.
606 	 * The app will probably crash because it will want to write into this non-existant buffer
607 	 * at some point. */
608 	if (ob == NULL)
609 	{
610 		LOG(4,("no overlay buffer specified\n"));
611 
612 		return B_ERROR;
613 	}
614 
615 	/* is this call done by the app that owns us? */
616 	if ((ot == NULL) || (si->overlay.myToken == NULL) || (ot != si->overlay.myToken))
617 	/* nope, abort */
618 	{
619 		LOG(4,("failed\n"));
620 
621 		return B_ERROR;
622 	}
623 	else
624 	/* call is for real */
625 	{
626 		/* find the buffer's offset */
627 		for (offset = 0; offset < MAXBUFFERS; offset++)
628 		{
629 			if (si->overlay.myBuffer[offset].buffer == ob->buffer) break;
630 		}
631 
632 		if (offset < MAXBUFFERS)
633 		{
634 			LOG(4,("succesfull, switching to buffer %d\n", offset));
635 
636 			gx00_configure_bes(ob, ow, ov, offset);
637 
638 			return B_OK;
639 		}
640 		else
641 		{
642 			/* this is no buffer of ours! */
643 			LOG(4,("buffer is not ours, aborted!\n"));
644 
645 			return B_ERROR;
646 		}
647 	}
648 }
649