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      1 /*
      2  * Copyright  2011 Intel Corporation
      3  *
      4  * Permission is hereby granted, free of charge, to any person obtaining a
      5  * copy of this software and associated documentation files (the "Software"),
      6  * to deal in the Software without restriction, including without limitation
      7  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
      8  * and/or sell copies of the Software, and to permit persons to whom the
      9  * Software is furnished to do so, subject to the following conditions:
     10  *
     11  * The above copyright notice and this permission notice (including the next
     12  * paragraph) shall be included in all copies or substantial portions of the
     13  * Software.
     14  *
     15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
     16  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
     17  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
     18  * NONINFRINGEMENT.  IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
     19  * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
     20  * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
     21  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
     22  * DEALINGS IN THE SOFTWARE.
     23  *
     24  * Authors:
     25  *    Benjamin Franzke <benjaminfranzke (at) googlemail.com>
     26  */
     27 
     28 #include <stddef.h>
     29 #include <stdio.h>
     30 #include <stdlib.h>
     31 #include <string.h>
     32 #include <stdint.h>
     33 
     34 #ifdef MAJOR_IN_MKDEV
     35 #include <sys/mkdev.h>
     36 #endif
     37 #ifdef MAJOR_IN_SYSMACROS
     38 #include <sys/sysmacros.h>
     39 #endif
     40 #include <sys/stat.h>
     41 #include <unistd.h>
     42 #include <errno.h>
     43 
     44 #include "gbm.h"
     45 #include "gbmint.h"
     46 #include "backend.h"
     47 
     48 /** Returns the file description for the gbm device
     49  *
     50  * \return The fd that the struct gbm_device was created with
     51  */
     52 GBM_EXPORT int
     53 gbm_device_get_fd(struct gbm_device *gbm)
     54 {
     55    return gbm->fd;
     56 }
     57 
     58 /** Get the backend name for the given gbm device
     59  *
     60  * \return The backend name string - this belongs to the device and must not
     61  * be freed
     62  */
     63 GBM_EXPORT const char *
     64 gbm_device_get_backend_name(struct gbm_device *gbm)
     65 {
     66    return gbm->name;
     67 }
     68 
     69 /** Test if a format is supported for a given set of usage flags.
     70  *
     71  * \param gbm The created buffer manager
     72  * \param format The format to test
     73  * \param usage A bitmask of the usages to test the format against
     74  * \return 1 if the format is supported otherwise 0
     75  *
     76  * \sa enum gbm_bo_flags for the list of flags that the format can be
     77  * tested against
     78  *
     79  * \sa enum gbm_bo_format for the list of formats
     80  */
     81 GBM_EXPORT int
     82 gbm_device_is_format_supported(struct gbm_device *gbm,
     83                                uint32_t format, uint32_t usage)
     84 {
     85    return gbm->is_format_supported(gbm, format, usage);
     86 }
     87 
     88 /** Get the number of planes that are required for a given format+modifier
     89  *
     90  * \param gbm The gbm device returned from gbm_create_device()
     91  * \param format The format to query
     92  * \param modifier The modifier to query
     93  */
     94 GBM_EXPORT int
     95 gbm_device_get_format_modifier_plane_count(struct gbm_device *gbm,
     96                                            uint32_t format,
     97                                            uint64_t modifier)
     98 {
     99    return gbm->get_format_modifier_plane_count(gbm, format, modifier);
    100 }
    101 
    102 /** Destroy the gbm device and free all resources associated with it.
    103  *
    104  * \param gbm The device created using gbm_create_device()
    105  */
    106 GBM_EXPORT void
    107 gbm_device_destroy(struct gbm_device *gbm)
    108 {
    109    gbm->refcount--;
    110    if (gbm->refcount == 0)
    111       gbm->destroy(gbm);
    112 }
    113 
    114 /** Create a gbm device for allocating buffers
    115  *
    116  * The file descriptor passed in is used by the backend to communicate with
    117  * platform for allocating the memory. For allocations using DRI this would be
    118  * the file descriptor returned when opening a device such as \c
    119  * /dev/dri/card0
    120  *
    121  * \param fd The file descriptor for a backend specific device
    122  * \return The newly created struct gbm_device. The resources associated with
    123  * the device should be freed with gbm_device_destroy() when it is no longer
    124  * needed. If the creation of the device failed NULL will be returned.
    125  */
    126 GBM_EXPORT struct gbm_device *
    127 gbm_create_device(int fd)
    128 {
    129    struct gbm_device *gbm = NULL;
    130    struct stat buf;
    131 
    132    if (fd < 0 || fstat(fd, &buf) < 0 || !S_ISCHR(buf.st_mode)) {
    133       errno = EINVAL;
    134       return NULL;
    135    }
    136 
    137    gbm = _gbm_create_device(fd);
    138    if (gbm == NULL)
    139       return NULL;
    140 
    141    gbm->dummy = gbm_create_device;
    142    gbm->stat = buf;
    143    gbm->refcount = 1;
    144 
    145    return gbm;
    146 }
    147 
    148 /** Get the width of the buffer object
    149  *
    150  * \param bo The buffer object
    151  * \return The width of the allocated buffer object
    152  *
    153  */
    154 GBM_EXPORT uint32_t
    155 gbm_bo_get_width(struct gbm_bo *bo)
    156 {
    157    return bo->width;
    158 }
    159 
    160 /** Get the height of the buffer object
    161  *
    162  * \param bo The buffer object
    163  * \return The height of the allocated buffer object
    164  */
    165 GBM_EXPORT uint32_t
    166 gbm_bo_get_height(struct gbm_bo *bo)
    167 {
    168    return bo->height;
    169 }
    170 
    171 /** Get the stride of the buffer object
    172  *
    173  * This is calculated by the backend when it does the allocation in
    174  * gbm_bo_create()
    175  *
    176  * \param bo The buffer object
    177  * \return The stride of the allocated buffer object in bytes
    178  */
    179 GBM_EXPORT uint32_t
    180 gbm_bo_get_stride(struct gbm_bo *bo)
    181 {
    182    return gbm_bo_get_stride_for_plane(bo, 0);
    183 }
    184 
    185 /** Get the stride for the given plane
    186  *
    187  * \param bo The buffer object
    188  * \param plane for which you want the stride
    189  *
    190  * \sa gbm_bo_get_stride()
    191  */
    192 GBM_EXPORT uint32_t
    193 gbm_bo_get_stride_for_plane(struct gbm_bo *bo, int plane)
    194 {
    195    return bo->gbm->bo_get_stride(bo, plane);
    196 }
    197 
    198 /** Get the format of the buffer object
    199  *
    200  * The format of the pixels in the buffer.
    201  *
    202  * \param bo The buffer object
    203  * \return The format of buffer object, one of the GBM_FORMAT_* codes
    204  */
    205 GBM_EXPORT uint32_t
    206 gbm_bo_get_format(struct gbm_bo *bo)
    207 {
    208    return bo->format;
    209 }
    210 
    211 /** Get the bit-per-pixel of the buffer object's format
    212  *
    213  * The bits-per-pixel of the buffer object's format.
    214  *
    215  * Note; The 'in-memory pixel' concept makes no sense for YUV formats
    216  * (pixels are the result of the combination of multiple memory sources:
    217  * Y, Cb & Cr; usually these are even in separate buffers), so YUV
    218  * formats are not supported by this function.
    219  *
    220  * \param bo The buffer object
    221  * \return The number of bits0per-pixel of the buffer object's format.
    222  */
    223 GBM_EXPORT uint32_t
    224 gbm_bo_get_bpp(struct gbm_bo *bo)
    225 {
    226    switch (bo->format) {
    227       default:
    228          return 0;
    229       case GBM_FORMAT_C8:
    230       case GBM_FORMAT_R8:
    231       case GBM_FORMAT_RGB332:
    232       case GBM_FORMAT_BGR233:
    233          return 8;
    234       case GBM_FORMAT_GR88:
    235       case GBM_FORMAT_XRGB4444:
    236       case GBM_FORMAT_XBGR4444:
    237       case GBM_FORMAT_RGBX4444:
    238       case GBM_FORMAT_BGRX4444:
    239       case GBM_FORMAT_ARGB4444:
    240       case GBM_FORMAT_ABGR4444:
    241       case GBM_FORMAT_RGBA4444:
    242       case GBM_FORMAT_BGRA4444:
    243       case GBM_FORMAT_XRGB1555:
    244       case GBM_FORMAT_XBGR1555:
    245       case GBM_FORMAT_RGBX5551:
    246       case GBM_FORMAT_BGRX5551:
    247       case GBM_FORMAT_ARGB1555:
    248       case GBM_FORMAT_ABGR1555:
    249       case GBM_FORMAT_RGBA5551:
    250       case GBM_FORMAT_BGRA5551:
    251       case GBM_FORMAT_RGB565:
    252       case GBM_FORMAT_BGR565:
    253          return 16;
    254       case GBM_FORMAT_RGB888:
    255       case GBM_FORMAT_BGR888:
    256          return 24;
    257       case GBM_FORMAT_XRGB8888:
    258       case GBM_FORMAT_XBGR8888:
    259       case GBM_FORMAT_RGBX8888:
    260       case GBM_FORMAT_BGRX8888:
    261       case GBM_FORMAT_ARGB8888:
    262       case GBM_FORMAT_ABGR8888:
    263       case GBM_FORMAT_RGBA8888:
    264       case GBM_FORMAT_BGRA8888:
    265       case GBM_FORMAT_XRGB2101010:
    266       case GBM_FORMAT_XBGR2101010:
    267       case GBM_FORMAT_RGBX1010102:
    268       case GBM_FORMAT_BGRX1010102:
    269       case GBM_FORMAT_ARGB2101010:
    270       case GBM_FORMAT_ABGR2101010:
    271       case GBM_FORMAT_RGBA1010102:
    272       case GBM_FORMAT_BGRA1010102:
    273          return 32;
    274    }
    275 }
    276 
    277 /** Get the offset for the data of the specified plane
    278  *
    279  * Extra planes, and even the first plane, may have an offset from the start of
    280  * the buffer object. This function will provide the offset for the given plane
    281  * to be used in various KMS APIs.
    282  *
    283  * \param bo The buffer object
    284  * \return The offset
    285  */
    286 GBM_EXPORT uint32_t
    287 gbm_bo_get_offset(struct gbm_bo *bo, int plane)
    288 {
    289    return bo->gbm->bo_get_offset(bo, plane);
    290 }
    291 
    292 /** Get the gbm device used to create the buffer object
    293  *
    294  * \param bo The buffer object
    295  * \return Returns the gbm device with which the buffer object was created
    296  */
    297 GBM_EXPORT struct gbm_device *
    298 gbm_bo_get_device(struct gbm_bo *bo)
    299 {
    300 	return bo->gbm;
    301 }
    302 
    303 /** Get the handle of the buffer object
    304  *
    305  * This is stored in the platform generic union gbm_bo_handle type. However
    306  * the format of this handle is platform specific.
    307  *
    308  * \param bo The buffer object
    309  * \return Returns the handle of the allocated buffer object
    310  */
    311 GBM_EXPORT union gbm_bo_handle
    312 gbm_bo_get_handle(struct gbm_bo *bo)
    313 {
    314    return bo->handle;
    315 }
    316 
    317 /** Get a DMA-BUF file descriptor for the buffer object
    318  *
    319  * This function creates a DMA-BUF (also known as PRIME) file descriptor
    320  * handle for the buffer object.  Each call to gbm_bo_get_fd() returns a new
    321  * file descriptor and the caller is responsible for closing the file
    322  * descriptor.
    323 
    324  * \param bo The buffer object
    325  * \return Returns a file descriptor referring to the underlying buffer or -1
    326  * if an error occurs.
    327  */
    328 GBM_EXPORT int
    329 gbm_bo_get_fd(struct gbm_bo *bo)
    330 {
    331    return bo->gbm->bo_get_fd(bo);
    332 }
    333 
    334 /** Get the number of planes for the given bo.
    335  *
    336  * \param bo The buffer object
    337  * \return The number of planes
    338  */
    339 GBM_EXPORT int
    340 gbm_bo_get_plane_count(struct gbm_bo *bo)
    341 {
    342    return bo->gbm->bo_get_planes(bo);
    343 }
    344 
    345 /** Get the handle for the specified plane of the buffer object
    346  *
    347  * This function gets the handle for any plane associated with the BO. When
    348  * dealing with multi-planar formats, or formats which might have implicit
    349  * planes based on different underlying hardware it is necessary for the client
    350  * to be able to get this information to pass to the DRM.
    351  *
    352  * \param bo The buffer object
    353  * \param plane the plane to get a handle for
    354  *
    355  * \sa gbm_bo_get_handle()
    356  */
    357 GBM_EXPORT union gbm_bo_handle
    358 gbm_bo_get_handle_for_plane(struct gbm_bo *bo, int plane)
    359 {
    360    return bo->gbm->bo_get_handle(bo, plane);
    361 }
    362 
    363 /**
    364  * Get the chosen modifier for the buffer object
    365  *
    366  * This function returns the modifier that was chosen for the object. These
    367  * properties may be generic, or platform/implementation dependent.
    368  *
    369  * \param bo The buffer object
    370  * \return Returns the selected modifier (chosen by the implementation) for the
    371  * BO.
    372  * \sa gbm_bo_create_with_modifiers() where possible modifiers are set
    373  * \sa gbm_surface_create_with_modifiers() where possible modifiers are set
    374  * \sa define DRM_FORMAT_MOD_* in drm_fourcc.h for possible modifiers
    375  */
    376 GBM_EXPORT uint64_t
    377 gbm_bo_get_modifier(struct gbm_bo *bo)
    378 {
    379    return bo->gbm->bo_get_modifier(bo);
    380 }
    381 
    382 /** Write data into the buffer object
    383  *
    384  * If the buffer object was created with the GBM_BO_USE_WRITE flag,
    385  * this function can be used to write data into the buffer object.  The
    386  * data is copied directly into the object and it's the responsibility
    387  * of the caller to make sure the data represents valid pixel data,
    388  * according to the width, height, stride and format of the buffer object.
    389  *
    390  * \param bo The buffer object
    391  * \param buf The data to write
    392  * \param count The number of bytes to write
    393  * \return Returns 0 on success, otherwise -1 is returned an errno set
    394  */
    395 GBM_EXPORT int
    396 gbm_bo_write(struct gbm_bo *bo, const void *buf, size_t count)
    397 {
    398    return bo->gbm->bo_write(bo, buf, count);
    399 }
    400 
    401 /** Set the user data associated with a buffer object
    402  *
    403  * \param bo The buffer object
    404  * \param data The data to associate to the buffer object
    405  * \param destroy_user_data A callback (which may be %NULL) that will be
    406  * called prior to the buffer destruction
    407  */
    408 GBM_EXPORT void
    409 gbm_bo_set_user_data(struct gbm_bo *bo, void *data,
    410 		     void (*destroy_user_data)(struct gbm_bo *, void *))
    411 {
    412    bo->user_data = data;
    413    bo->destroy_user_data = destroy_user_data;
    414 }
    415 
    416 /** Get the user data associated with a buffer object
    417  *
    418  * \param bo The buffer object
    419  * \return Returns the user data associated with the buffer object or %NULL
    420  * if no data was associated with it
    421  *
    422  * \sa gbm_bo_set_user_data()
    423  */
    424 GBM_EXPORT void *
    425 gbm_bo_get_user_data(struct gbm_bo *bo)
    426 {
    427    return bo->user_data;
    428 }
    429 
    430 /**
    431  * Destroys the given buffer object and frees all resources associated with
    432  * it.
    433  *
    434  * \param bo The buffer object
    435  */
    436 GBM_EXPORT void
    437 gbm_bo_destroy(struct gbm_bo *bo)
    438 {
    439    if (bo->destroy_user_data)
    440       bo->destroy_user_data(bo, bo->user_data);
    441 
    442    bo->gbm->bo_destroy(bo);
    443 }
    444 
    445 /**
    446  * Allocate a buffer object for the given dimensions
    447  *
    448  * \param gbm The gbm device returned from gbm_create_device()
    449  * \param width The width for the buffer
    450  * \param height The height for the buffer
    451  * \param format The format to use for the buffer
    452  * \param usage The union of the usage flags for this buffer
    453  *
    454  * \return A newly allocated buffer that should be freed with gbm_bo_destroy()
    455  * when no longer needed. If an error occurs during allocation %NULL will be
    456  * returned and errno set.
    457  *
    458  * \sa enum gbm_bo_format for the list of formats
    459  * \sa enum gbm_bo_flags for the list of usage flags
    460  */
    461 GBM_EXPORT struct gbm_bo *
    462 gbm_bo_create(struct gbm_device *gbm,
    463               uint32_t width, uint32_t height,
    464               uint32_t format, uint32_t usage)
    465 {
    466    if (width == 0 || height == 0) {
    467       errno = EINVAL;
    468       return NULL;
    469    }
    470 
    471    return gbm->bo_create(gbm, width, height, format, usage, NULL, 0);
    472 }
    473 
    474 GBM_EXPORT struct gbm_bo *
    475 gbm_bo_create_with_modifiers(struct gbm_device *gbm,
    476                              uint32_t width, uint32_t height,
    477                              uint32_t format,
    478                              const uint64_t *modifiers,
    479                              const unsigned int count)
    480 {
    481    if (width == 0 || height == 0) {
    482       errno = EINVAL;
    483       return NULL;
    484    }
    485 
    486    if ((count && !modifiers) || (modifiers && !count)) {
    487       errno = EINVAL;
    488       return NULL;
    489    }
    490 
    491    return gbm->bo_create(gbm, width, height, format, 0, modifiers, count);
    492 }
    493 /**
    494  * Create a gbm buffer object from an foreign object
    495  *
    496  * This function imports a foreign object and creates a new gbm bo for it.
    497  * This enabled using the foreign object with a display API such as KMS.
    498  * Currently three types of foreign objects are supported, indicated by the type
    499  * argument:
    500  *
    501  *   GBM_BO_IMPORT_WL_BUFFER
    502  *   GBM_BO_IMPORT_EGL_IMAGE
    503  *   GBM_BO_IMPORT_FD
    504  *
    505  * The gbm bo shares the underlying pixels but its life-time is
    506  * independent of the foreign object.
    507  *
    508  * \param gbm The gbm device returned from gbm_create_device()
    509  * \param type The type of object we're importing
    510  * \param buffer Pointer to the external object
    511  * \param usage The union of the usage flags for this buffer
    512  *
    513  * \return A newly allocated buffer object that should be freed with
    514  * gbm_bo_destroy() when no longer needed. On error, %NULL is returned
    515  * and errno is set.
    516  *
    517  * \sa enum gbm_bo_flags for the list of usage flags
    518  */
    519 GBM_EXPORT struct gbm_bo *
    520 gbm_bo_import(struct gbm_device *gbm,
    521               uint32_t type, void *buffer, uint32_t usage)
    522 {
    523    return gbm->bo_import(gbm, type, buffer, usage);
    524 }
    525 
    526 /**
    527  * Map a region of a gbm buffer object for cpu access
    528  *
    529  * This function maps a region of a gbm bo for cpu read and/or write
    530  * access.
    531  *
    532  * \param bo The buffer object
    533  * \param x The X (top left origin) starting position of the mapped region for
    534  * the buffer
    535  * \param y The Y (top left origin) starting position of the mapped region for
    536  * the buffer
    537  * \param width The width of the mapped region for the buffer
    538  * \param height The height of the mapped region for the buffer
    539  * \param flags The union of the GBM_BO_TRANSFER_* flags for this buffer
    540  * \param stride Ptr for returned stride in bytes of the mapped region
    541  * \param map_data Returned opaque ptr for the mapped region
    542  *
    543  * \return Address of the mapped buffer that should be unmapped with
    544  * gbm_bo_unmap() when no longer needed. On error, %NULL is returned
    545  * and errno is set.
    546  *
    547  * \sa enum gbm_bo_transfer_flags for the list of flags
    548  */
    549 GBM_EXPORT void *
    550 gbm_bo_map(struct gbm_bo *bo,
    551               uint32_t x, uint32_t y,
    552               uint32_t width, uint32_t height,
    553               uint32_t flags, uint32_t *stride, void **map_data)
    554 {
    555    if (!bo || width == 0 || height == 0 || !stride || !map_data) {
    556       errno = EINVAL;
    557       return NULL;
    558    }
    559 
    560    return bo->gbm->bo_map(bo, x, y, width, height,
    561                           flags, stride, map_data);
    562 }
    563 
    564 /**
    565  * Unmap a previously mapped region of a gbm buffer object
    566  *
    567  * This function unmaps a region of a gbm bo for cpu read and/or write
    568  * access.
    569  *
    570  * \param bo The buffer object
    571  * \param map_data opaque ptr returned from prior gbm_bo_map
    572  */
    573 GBM_EXPORT void
    574 gbm_bo_unmap(struct gbm_bo *bo, void *map_data)
    575 {
    576    bo->gbm->bo_unmap(bo, map_data);
    577 }
    578 
    579 /**
    580  * Allocate a surface object
    581  *
    582  * \param gbm The gbm device returned from gbm_create_device()
    583  * \param width The width for the surface
    584  * \param height The height for the surface
    585  * \param format The format to use for the surface
    586  *
    587  * \return A newly allocated surface that should be freed with
    588  * gbm_surface_destroy() when no longer needed. If an error occurs
    589  * during allocation %NULL will be returned.
    590  *
    591  * \sa enum gbm_bo_format for the list of formats
    592  */
    593 GBM_EXPORT struct gbm_surface *
    594 gbm_surface_create(struct gbm_device *gbm,
    595                    uint32_t width, uint32_t height,
    596 		   uint32_t format, uint32_t flags)
    597 {
    598    return gbm->surface_create(gbm, width, height, format, flags, NULL, 0);
    599 }
    600 
    601 GBM_EXPORT struct gbm_surface *
    602 gbm_surface_create_with_modifiers(struct gbm_device *gbm,
    603                                   uint32_t width, uint32_t height,
    604                                   uint32_t format,
    605                                   const uint64_t *modifiers,
    606                                   const unsigned int count)
    607 {
    608    if ((count && !modifiers) || (modifiers && !count)) {
    609       errno = EINVAL;
    610       return NULL;
    611    }
    612 
    613    return gbm->surface_create(gbm, width, height, format, 0,
    614                               modifiers, count);
    615 }
    616 
    617 /**
    618  * Destroys the given surface and frees all resources associated with
    619  * it.
    620  *
    621  * All buffers locked with gbm_surface_lock_front_buffer() should be
    622  * released prior to calling this function.
    623  *
    624  * \param surf The surface
    625  */
    626 GBM_EXPORT void
    627 gbm_surface_destroy(struct gbm_surface *surf)
    628 {
    629    surf->gbm->surface_destroy(surf);
    630 }
    631 
    632 /**
    633  * Lock the surface's current front buffer
    634  *
    635  * Lock rendering to the surface's current front buffer until it is
    636  * released with gbm_surface_release_buffer().
    637  *
    638  * This function must be called exactly once after calling
    639  * eglSwapBuffers.  Calling it before any eglSwapBuffer has happened
    640  * on the surface or two or more times after eglSwapBuffers is an
    641  * error.  A new bo representing the new front buffer is returned.  On
    642  * multiple invocations, all the returned bos must be released in
    643  * order to release the actual surface buffer.
    644  *
    645  * \param surf The surface
    646  *
    647  * \return A buffer object that should be released with
    648  * gbm_surface_release_buffer() when no longer needed.  The implementation
    649  * is free to reuse buffers released with gbm_surface_release_buffer() so
    650  * this bo should not be destroyed using gbm_bo_destroy().  If an error
    651  * occurs this function returns %NULL.
    652  */
    653 GBM_EXPORT struct gbm_bo *
    654 gbm_surface_lock_front_buffer(struct gbm_surface *surf)
    655 {
    656    return surf->gbm->surface_lock_front_buffer(surf);
    657 }
    658 
    659 /**
    660  * Release a locked buffer obtained with gbm_surface_lock_front_buffer()
    661  *
    662  * Returns the underlying buffer to the gbm surface.  Releasing a bo
    663  * will typically make gbm_surface_has_free_buffer() return 1 and thus
    664  * allow rendering the next frame, but not always. The implementation
    665  * may choose to destroy the bo immediately or reuse it, in which case
    666  * the user data associated with it is unchanged.
    667  *
    668  * \param surf The surface
    669  * \param bo The buffer object
    670  */
    671 GBM_EXPORT void
    672 gbm_surface_release_buffer(struct gbm_surface *surf, struct gbm_bo *bo)
    673 {
    674    surf->gbm->surface_release_buffer(surf, bo);
    675 }
    676 
    677 /**
    678  * Return whether or not a surface has free (non-locked) buffers
    679  *
    680  * Before starting a new frame, the surface must have a buffer
    681  * available for rendering.  Initially, a gbm surface will have a free
    682  * buffer, but after one or more buffers have been locked (\sa
    683  * gbm_surface_lock_front_buffer()), the application must check for a
    684  * free buffer before rendering.
    685  *
    686  * If a surface doesn't have a free buffer, the application must
    687  * return a buffer to the surface using gbm_surface_release_buffer()
    688  * and after that, the application can query for free buffers again.
    689  *
    690  * \param surf The surface
    691  * \return 1 if the surface has free buffers, 0 otherwise
    692  */
    693 GBM_EXPORT int
    694 gbm_surface_has_free_buffers(struct gbm_surface *surf)
    695 {
    696    return surf->gbm->surface_has_free_buffers(surf);
    697 }
    698