gbm: Add documentation for the public facing API

3 files changed, 162 insertions, 2 deletions

diff --git a/src/gbm/main/gbm.c b/src/gbm/main/gbm.c
index 8440b2c6ae3..3e24c4af011 100644
--- a/src/gbm/main/gbm.c
+++ b/src/gbm/main/gbm.c
@@ -48,6 +48,10 @@ struct gbm_device *devices[16];
 
 static int device_num = 0;
 
+/** Returns the file description for the gbm device
+ *
+ * \return The fd that the struct gbm_device was created with
+ */
 GBM_EXPORT int
 gbm_device_get_fd(struct gbm_device *gbm)
 {
@@ -55,12 +59,29 @@ gbm_device_get_fd(struct gbm_device *gbm)
 }
 
 /* FIXME: maybe superfluous, use udev subclass from the fd? */
+/** Get the backend name for the given gbm device
+ *
+ * \return The backend name string - this belongs to the device and must not
+ * be freed
+ */
 GBM_EXPORT const char *
 gbm_device_get_backend_name(struct gbm_device *gbm)
 {
    return gbm->name;
 }
 
+/** Test if a format is supported for a given set of usage flags.
+ *
+ * \param gbm The created buffer manager
+ * \param format The format to test
+ * \param usage A bitmask of the usages to test the format against
+ * \return 1 if the format is supported otherwise 0
+ *
+ * \sa enum gbm_bo_flags for the list of flags that the format can be
+ * tested against
+ *
+ * \sa enum gbm_bo_format for the list of formats
+ */
 int
 gbm_device_is_format_supported(struct gbm_device *gbm,
                                enum gbm_bo_format format,
@@ -69,6 +90,10 @@ gbm_device_is_format_supported(struct gbm_device *gbm,
    return gbm->is_format_supported(gbm, format, usage);
 }
 
+/** Destroy the gbm device and free all resources associated with it.
+ *
+ * \param gbm The device created using gbm_create_device()
+ */
 GBM_EXPORT void
 gbm_device_destroy(struct gbm_device *gbm)
 {
@@ -103,6 +128,18 @@ _gbm_mesa_get_device(int fd)
    return gbm;
 }
 
+/** Create a gbm device for allocating buffers
+ *
+ * The file descriptor passed in is used by the backend to communicate with
+ * platform for allocating the memory. For allocations using DRI this would be
+ * the file descriptor returned when opening a device such as \c
+ * /dev/dri/card0
+ *
+ * \param fd The file descriptor for an backend specific device
+ * \return The newly created struct gbm_device. The resources associated with
+ * the device should be freed with gbm_device_destroy() when it is no longer
+ * needed. If the creation of the device failed NULL will be returned.
+ */
 GBM_EXPORT struct gbm_device *
 gbm_create_device(int fd)
 {
@@ -131,36 +168,85 @@ gbm_create_device(int fd)
    return gbm;
 }
 
+/** Get the width of the buffer object
+ *
+ * \param bo The buffer object
+ * \return The width of the allocated buffer object
+ *
+ */
 GBM_EXPORT unsigned int
 gbm_bo_get_width(struct gbm_bo *bo)
 {
    return bo->width;
 }
 
+/** Get the height of the buffer object
+ *
+ * \param bo The buffer object
+ * \return The height of the allocated buffer object
+ */
 GBM_EXPORT unsigned int
 gbm_bo_get_height(struct gbm_bo *bo)
 {
    return bo->height;
 }
 
+/** Get the stride of the buffer object
+ *
+ * This is calculated by the backend when it does the allocation in
+ * gbm_bo_create()
+ *
+ * \param bo The buffer object
+ * \return The stride of the allocated buffer object
+ */
 GBM_EXPORT uint32_t
 gbm_bo_get_pitch(struct gbm_bo *bo)
 {
    return bo->pitch;
 }
 
+/** Get the handle of the buffer object
+ *
+ * This is stored in the platform generic union gbm_bo_handle type. However
+ * the format of this handle is platform specific.
+ *
+ * \param bo The buffer object
+ * \return Returns the stride of the allocated buffer object
+ */
 GBM_EXPORT union gbm_bo_handle
 gbm_bo_get_handle(struct gbm_bo *bo)
 {
    return bo->handle;
 }
 
+/**
+ * Destroys the given buffer object and frees all resources associated with
+ * it.
+ *
+ * \param bo The buffer object
+ */
 GBM_EXPORT void
 gbm_bo_destroy(struct gbm_bo *bo)
 {
    bo->gbm->bo_destroy(bo);
 }
 
+/**
+ * Allocate a buffer object for the given dimensions
+ *
+ * \param gbm The gbm device returned from gbm_create_device()
+ * \param width The width for the buffer
+ * \param height The height for the buffer
+ * \param format The format to use for the buffer
+ * \param usage The union of the usage flags for this buffer
+ *
+ * \return A newly allocated buffer that should be freed with gbm_bo_destroy()
+ * when no longer needed. If an error occurs during allocation %NULL will be
+ * returned.
+ *
+ * \sa enum gbm_bo_format for the list of formats
+ * \sa enum gbm_bo_flags for the list of usage flags
+ */
 GBM_EXPORT struct gbm_bo *
 gbm_bo_create(struct gbm_device *gbm,
               uint32_t width, uint32_t height,
@@ -176,6 +262,24 @@ gbm_bo_create(struct gbm_device *gbm,
    return gbm->bo_create(gbm, width, height, format, usage);
 }
 
+/**
+ * Create a buffer object representing the contents of an EGLImage
+ *
+ * \param gbm The gbm device returned from gbm_create_device()
+ * \param egl_dpy The EGLDisplay on which the EGLImage was created
+ * \param egl_image The EGLImage to create the buffer from
+ * \param width The width to use in the creation of the buffer object
+ * \param height The height to use in the creation of the buffer object
+ * \param usage The union of the usage flags for this buffer
+ *
+ * \return A newly allocated buffer object that should be freed with
+ * gbm_bo_destroy() when no longer needed.
+ *
+ * \sa enum gbm_bo_flags for the list of usage flags
+ *
+ * \note The expectation is that this function will use an efficient method
+ * for making the contents of the EGLImage available as a buffer object.
+ */
 GBM_EXPORT struct gbm_bo *
 gbm_bo_create_from_egl_image(struct gbm_device *gbm,
                              void *egl_dpy, void *egl_image,
diff --git a/src/gbm/main/gbm.h b/src/gbm/main/gbm.h
index 05d2292dc75..c4ae51db022 100644
--- a/src/gbm/main/gbm.h
+++ b/src/gbm/main/gbm.h
@@ -37,9 +37,28 @@ extern "C" {
 
 #include <stdint.h>
 
+/**
+ * \file gbm.h
+ * \brief Generic Buffer Manager
+ */
+
 struct gbm_device;
 struct gbm_bo;
 
+/**
+ * \mainpage The Generic Buffer Manager
+ *
+ * This module provides an abstraction that the caller can use to request a
+ * buffer from the underlying memory management system for the platform.
+ *
+ * This allows the creation of portable code whilst still allowing access to
+ * the underlying memory manager.
+ */
+
+/**
+ * Abstraction representing the handle to a buffer allocated by the
+ * manager
+ */
 union gbm_bo_handle {
    void *ptr;
    int32_t s32;
@@ -48,14 +67,36 @@ union gbm_bo_handle {
    uint64_t u64;
 };
 
+/** Format of the allocated buffer */
 enum gbm_bo_format {
-   GBM_BO_FORMAT_XRGB8888,
-   GBM_BO_FORMAT_ARGB8888,
+   /** RGB with 8 bits per channel in a 32 bit value */
+   GBM_BO_FORMAT_XRGB8888, 
+   /** ARGB with 8 bits per channel in a 32 bit value */
+   GBM_BO_FORMAT_ARGB8888
 };
 
+/**
+ * Flags to indicate the intended use for the buffer - these are passed into
+ * gbm_bo_create(). The caller must set the union of all the flags that are
+ * appropriate
+ *
+ * \sa Use gbm_device_is_format_supported() to check if the combination of format
+ * and use flags are supported
+ */
 enum gbm_bo_flags {
+   /**
+    * Buffer is going to be presented to the screen using an API such as KMS
+    */
    GBM_BO_USE_SCANOUT      = (1 << 0),
+   /**
+    * Buffer is going to be used as cursor - the dimensions for the buffer
+    * must be 64x64 if this flag is passed.
+    */
    GBM_BO_USE_CURSOR_64X64 = (1 << 1),
+   /**
+    * Buffer is to be used for rendering - for example it is going to be used
+    * as the storage for a color buffer
+    */
    GBM_BO_USE_RENDERING    = (1 << 2),
 };
 
diff --git a/src/gbm/main/gbmint.h b/src/gbm/main/gbmint.h
index fb8db804c1b..9e4072ef6ea 100644
--- a/src/gbm/main/gbmint.h
+++ b/src/gbm/main/gbmint.h
@@ -38,6 +38,16 @@
 #define GBM_EXPORT
 #endif
 
+/**
+ * \file gbmint.h
+ * \brief Internal implementation details of gbm
+ */
+
+/**
+ * The device used for the memory allocation.
+ *
+ * The members of this structure should be not accessed directly
+ */
 struct gbm_device {
    /* Hack to make a gbm_device detectable by its first element. */
    struct gbm_device *(*dummy)(int);
@@ -63,6 +73,11 @@ struct gbm_device {
    void (*bo_destroy)(struct gbm_bo *bo);
 };
 
+/**
+ * The allocated buffer object.
+ *
+ * The members in this structure should not be accessed directly.
+ */
 struct gbm_bo {
    struct gbm_device *gbm;
    uint32_t width;