Function mtp_attn_meta_batch_dev 

pub fn mtp_attn_meta_batch_dev(base: DevicePtr, n: usize) -> AttnMetadataDev

2026-09-30: The attention metadata pack_mtp_attn_meta_batch lays out at base for n rows (MtpBatchMetaLayout); max_blocks_per_seq is the step’s, set by its reader.