1.20. V4L2 Memory to Memory functions and data structures

struct v4l2_m2m_ops

mem-to-mem device driver callbacks

Definition

struct v4l2_m2m_ops {
  void (* device_run) (void *priv);
  int (* job_ready) (void *priv);
  void (* job_abort) (void *priv);
  void (* lock) (void *priv);
  void (* unlock) (void *priv);
};

Members

void (*)(void *priv) device_run

required. Begin the actual job (transaction) inside this callback. The job does NOT have to end before this callback returns (and it will be the usual case). When the job finishes, v4l2_m2m_job_finish() has to be called.

int (*)(void *priv) job_ready

optional. Should return 0 if the driver does not have a job fully prepared to run yet (i.e. it will not be able to finish a transaction without sleeping). If not provided, it will be assumed that one source and one destination buffer are all that is required for the driver to perform one full transaction. This method may not sleep.

void (*)(void *priv) job_abort

required. Informs the driver that it has to abort the currently running transaction as soon as possible (i.e. as soon as it can stop the device safely; e.g. in the next interrupt handler), even if the transaction would not have been finished by then. After the driver performs the necessary steps, it has to call v4l2_m2m_job_finish() (as if the transaction ended normally). This function does not have to (and will usually not) wait until the device enters a state when it can be stopped.

void (*)(void *priv) lock

optional. Define a driver’s own lock callback, instead of using m2m_ctx->q_lock.

void (*)(void *priv) unlock

optional. Define a driver’s own unlock callback, instead of using m2m_ctx->q_lock.

unsigned int v4l2_m2m_num_src_bufs_ready(struct v4l2_m2m_ctx * m2m_ctx)

return the number of source buffers ready for use

Parameters

struct v4l2_m2m_ctx * m2m_ctx

pointer to struct v4l2_m2m_ctx

unsigned int v4l2_m2m_num_dst_bufs_ready(struct v4l2_m2m_ctx * m2m_ctx)

return the number of destination buffers ready for use

Parameters

struct v4l2_m2m_ctx * m2m_ctx

pointer to struct v4l2_m2m_ctx

void * v4l2_m2m_next_src_buf(struct v4l2_m2m_ctx * m2m_ctx)

return next source buffer from the list of ready buffers

Parameters

struct v4l2_m2m_ctx * m2m_ctx

pointer to struct v4l2_m2m_ctx

void * v4l2_m2m_next_dst_buf(struct v4l2_m2m_ctx * m2m_ctx)

return next destination buffer from the list of ready buffers

Parameters

struct v4l2_m2m_ctx * m2m_ctx

pointer to struct v4l2_m2m_ctx

struct vb2_queue * v4l2_m2m_get_src_vq(struct v4l2_m2m_ctx * m2m_ctx)

return vb2_queue for source buffers

Parameters

struct v4l2_m2m_ctx * m2m_ctx

pointer to struct v4l2_m2m_ctx

struct vb2_queue * v4l2_m2m_get_dst_vq(struct v4l2_m2m_ctx * m2m_ctx)

return vb2_queue for destination buffers

Parameters

struct v4l2_m2m_ctx * m2m_ctx

pointer to struct v4l2_m2m_ctx

void * v4l2_m2m_src_buf_remove(struct v4l2_m2m_ctx * m2m_ctx)

take off a source buffer from the list of ready buffers and return it

Parameters

struct v4l2_m2m_ctx * m2m_ctx

pointer to struct v4l2_m2m_ctx

void * v4l2_m2m_dst_buf_remove(struct v4l2_m2m_ctx * m2m_ctx)

take off a destination buffer from the list of ready buffers and return it

Parameters

struct v4l2_m2m_ctx * m2m_ctx

pointer to struct v4l2_m2m_ctx