static int dma_buf_prepare(BMDMAState *bm, int is_write) { IDEState *s = bmdma_active_if(bm); struct { uint32_t addr; uint32_t size; } prd; int l, len; qemu_sglist_init(&s->sg, s->nsector / (TARGET_PAGE_SIZE/512) + 1); s->io_buffer_size = 0; for(;;) { if (bm->cur_prd_len == 0) { /* end of table (with a fail safe of one page) */ if (bm->cur_prd_last || (bm->cur_addr - bm->addr) >= 4096) return s->io_buffer_size != 0; cpu_physical_memory_read(bm->cur_addr, (uint8_t *)&prd, 8); bm->cur_addr += 8; prd.addr = le32_to_cpu(prd.addr); prd.size = le32_to_cpu(prd.size); len = prd.size & 0xfffe; if (len == 0) len = 0x10000; bm->cur_prd_len = len; bm->cur_prd_addr = prd.addr; bm->cur_prd_last = (prd.size & 0x80000000); } l = bm->cur_prd_len; if (l > 0) { qemu_sglist_add(&s->sg, bm->cur_prd_addr, l); bm->cur_prd_addr += l; bm->cur_prd_len -= l; s->io_buffer_size += l; } } return 1; }