Command Buffer¶

API reference for the GNM command buffer, the core object used to record GPU commands for submission to the graphics queue.

Header: gnm_commandbuffer.h

Types¶

GnmCommandCallbackFunc¶

Function pointer type for a command buffer callback. Invoked when the command buffer needs to emit or process a command.

typedef bool (*GnmCommandCallbackFunc)(
    GnmCommandBuffer* cb, uint32_t sizedwords, void* userdata
);

Parameter	Type	Description
`cb`	`GnmCommandBuffer*`	The command buffer being processed
`sizedwords`	`uint32_t`	Size of the command in DWORDs
`userdata`	`void*`	User-supplied opaque pointer

Returns: bool — true if the callback handled the command successfully.

GnmCommandCallback¶

Pairs a callback function with its user data pointer.

typedef struct {
    GnmCommandCallbackFunc func;
    void* userdata;
} GnmCommandCallback;

Field	Type	Description
`func`	`GnmCommandCallbackFunc`	The callback function to invoke
`userdata`	`void*`	Opaque pointer passed to `func` on each call

GnmCommandBufferFlags¶

Bitfield flags controlling command buffer behavior.

typedef struct {
    uint64_t predication_enabled : 1;
    uint64_t shadertype : 1;
    uint64_t _unused : 62;
} GnmCommandBufferFlags;

Field	Type (bits)	Description
`predation_enabled`	`uint64_t : 1`	Whether predation is enabled for this buffer
`shadertype`	`uint64_t : 1`	Shader type flag
`_unused`	`uint64_t : 62`	Reserved / unused bits

GnmCommandBuffer¶

The command buffer structure. Occupies exactly 0x40 (64) bytes.

struct GnmCommandBuffer {
    uint32_t* beginptr;
    uint32_t* endptr;
    uint32_t* cmdptr;

    GnmCommandCallback callback;
    GnmCommandBufferFlags flags;

    uint64_t _unused;
    uint32_t sizedwords;
    uint32_t _unused2;
};

Field	Type	Offset	Description
`beginptr`	`uint32_t*`	`0x00`	Pointer to the start of the command buffer memory
`endptr`	`uint32_t*`	`0x08`	Pointer to the end (one past the last usable DWORD) of the buffer
`cmdptr`	`uint32_t*`	`0x10`	Current write cursor — next command will be written here
`callback`	`GnmCommandCallback`	`0x18`	Callback function and user data for command emission
`flags`	`GnmCommandBufferFlags`	`0x28`	Bitfield flags (predation, shader type)
`_unused`	`uint64_t`	`0x30`	Reserved
`sizedwords`	`uint32_t`	`0x38`	Total size of the buffer in DWORDs
`_unused2`	`uint32_t`	`0x3C`	Reserved

Static Assert¶

_Static_assert(sizeof(GnmCommandBuffer) == 0x40, "");

The structure is guaranteed to be exactly 64 bytes.

Functions¶

sceGnmCmdInit¶

Initializes a GnmCommandBuffer from a block of memory and an optional callback.

GnmCommandBuffer sceGnmCmdInit(
    void* buffer, uint32_t bytesize, GnmCommandCallbackFunc* cb, void* cbdata
);

Parameter	Type	Description
`buffer`	`void*`	Pointer to the memory backing the command buffer
`bytesize`	`uint32_t`	Size of `buffer` in bytes
`cb`	`GnmCommandCallbackFunc*`	Optional callback function (may be `NULL`)
`cbdata`	`void*`	Opaque data passed to the callback

Returns: GnmCommandBuffer — an initialized command buffer value.

sceGnmCmdReset¶

Resets the command buffer's write cursor back to the beginning, discarding all previously recorded commands. This is an inline function.

static inline void sceGnmCmdReset(GnmCommandBuffer* cmd) {
    cmd->cmdptr = cmd->beginptr;
}

Parameter	Type	Description
`cmd`	`GnmCommandBuffer*`	The command buffer to reset

sceGnmCmdAllocInside¶

Allocates space inside the command buffer with a specified size and alignment.

void* sceGnmCmdAllocInside(
    GnmCommandBuffer* cmd, uint32_t size, uint32_t alignment
);

Parameter	Type	Description
`cmd`	`GnmCommandBuffer*`	The command buffer to allocate from
`size`	`uint32_t`	Number of bytes to allocate
`alignment`	`uint32_t`	Required alignment of the returned pointer

Returns: void* — pointer to the allocated region, or NULL on failure.