/* * Sample fifo dma implementation * * Copyright (C) 2010 Stefani Seibold * * Released under the GPL version 2 only. * */ #include #include #include /* * This module shows how to handle fifo dma operations. */ /* fifo size in elements (bytes) */ #define FIFO_SIZE 32 static struct kfifo fifo; static int __init example_init(void) { int i; unsigned int ret; struct scatterlist sg[10]; printk(KERN_INFO "DMA fifo test start\n"); if (kfifo_alloc(&fifo, FIFO_SIZE, GFP_KERNEL)) { printk(KERN_ERR "error kfifo_alloc\n"); return 1; } printk(KERN_INFO "queue size: %u\n", kfifo_size(&fifo)); kfifo_in(&fifo, "test", 4); for (i = 0; i != 9; i++) kfifo_put(&fifo, &i); /* kick away first byte */ ret = kfifo_get(&fifo, &i); printk(KERN_INFO "queue len: %u\n", kfifo_len(&fifo)); sg_init_table(sg, ARRAY_SIZE(sg)); ret = kfifo_dma_in_prepare(&fifo, sg, ARRAY_SIZE(sg), FIFO_SIZE); printk(KERN_INFO "DMA sgl entries: %d\n", ret); /* if 0 was returned, fifo is full and no sgl was created */ if (ret) { printk(KERN_INFO "scatterlist for receive:\n"); for (i = 0; i < ARRAY_SIZE(sg); i++) { printk(KERN_INFO "sg[%d] -> " "page_link 0x%.8lx offset 0x%.8x length 0x%.8x\n", i, sg[i].page_link, sg[i].offset, sg[i].length); if (sg_is_last(&sg[i])) break; } /* but here your code to setup and exectute the dma operation */ /* ... */ /* example: zero bytes received */ ret = 0; /* finish the dma operation and update the received data */ kfifo_dma_in_finish(&fifo, ret); } ret = kfifo_dma_out_prepare(&fifo, sg, ARRAY_SIZE(sg), 8); printk(KERN_INFO "DMA sgl entries: %d\n", ret); /* if 0 was returned, no data was available and no sgl was created */ if (ret) { printk(KERN_INFO "scatterlist for transmit:\n"); for (i = 0; i < ARRAY_SIZE(sg); i++) { printk(KERN_INFO "sg[%d] -> " "page_link 0x%.8lx offset 0x%.8x length 0x%.8x\n", i, sg[i].page_link, sg[i].offset, sg[i].length); if (sg_is_last(&sg[i])) break; } /* but here your code to setup and exectute the dma operation */ /* ... */ /* example: 5 bytes transmitted */ ret = 5; /* finish the dma operation and update the transmitted data */ kfifo_dma_out_finish(&fifo, ret); } printk(KERN_INFO "queue len: %u\n", kfifo_len(&fifo)); return 0; } static void __exit example_exit(void) { #ifdef DYNAMIC kfifo_free(&test); #endif } module_init(example_init); module_exit(example_exit); MODULE_LICENSE("GPL"); MODULE_AUTHOR("Stefani Seibold ");