Further information here: http://www.kernel-labs.org/?q=blockdriver http://www.kernel-labs.org/?q=blockiolayer and kernel source drivers/block subdirectory, looking for all the register_blkdev() caller, all these can be your potential block devices examples. whether they used BIO or not it depends. For example: ./brd.c: if (register_blkdev(RAMDISK_MAJOR, "ramdisk")) unregister_blkdev(RAMDISK_MAJOR, "ramdisk"); And inside brd.c look at how the API blk_queue_make_request() is used for customization of special request structure, so bio is manipulated in this brd.c. But others like DAC960.c, virtio_blk.c etc does not touch the bio internals, but deals at the request and request_queue level instead. It leave the internals at the block/*.c implementation. For example, for virtio_blk.c, it uses blk_rq_map_sg(): /* * map a request to scatterlist, return number of sg entries setup. Caller * must make sure sg can hold rq->nr_phys_segments entries */ int blk_rq_map_sg(struct request_queue *q, struct request *rq, struct scatterlist *sglist) { struct bio_vec *bvec, *bvprv; struct req_iterator iter; struct scatterlist *sg; for BIO mapping. but then my generalization may be wrong? On Wed, Sep 10, 2008 at 7:37 AM, Peter Teoh <htmldeveloper@xxxxxxxxx> wrote: > On Wed, Sep 10, 2008 at 12:51 AM, Rohit Sharma <imreckless@xxxxxxxxx> wrote: >> I was going through block drivers, >> i am not able to associate request queues and bio structures. >> How are the requests processed using bio structures. >> Can anyone provide me with block driver example or tutorial. >> > > looking at block/scsi_ioctl.c:sg_io() function - does line 207 and 241 > answer your question? > > 207 rq = blk_get_request(q, writing ? WRITE : READ, GFP_KERNEL); > 208 if (!rq) > 209 return -ENOMEM; > 210 > 211 if (blk_fill_sghdr_rq(q, rq, hdr, file)) { > 212 blk_put_request(rq); > 213 return -EFAULT; > 214 } > 215 > 216 if (hdr->iovec_count) { > 217 const int size = sizeof(struct sg_iovec) * hdr->iovec_count; > 218 struct sg_iovec *iov; > 219 > 220 iov = kmalloc(size, GFP_KERNEL); > 221 if (!iov) { > 222 ret = -ENOMEM; > 223 goto out; > 224 } > 225 > 226 if (copy_from_user(iov, hdr->dxferp, size)) { > 227 kfree(iov); > 228 ret = -EFAULT; > 229 goto out; > 230 } > 231 > 232 ret = blk_rq_map_user_iov(q, rq, iov, hdr->iovec_count, > 233 hdr->dxfer_len); > 234 kfree(iov); > 235 } else if (hdr->dxfer_len) > 236 ret = blk_rq_map_user(q, rq, hdr->dxferp, hdr->dxfer_len); > 237 > 238 if (ret) > 239 goto out; > 240 > 241 bio = rq->bio; > 242 memset(sense, 0, sizeof(sense)); > 243 rq->sense = sense; > 244 rq->sense_len = 0; > 245 rq->retries = 0; > 246 > 247 start_time = jiffies; > 248 > 249 /* ignore return value. All information is passed back to caller > 250 * (if he doesn't check that is his problem). > 251 * N.B. a non-zero SCSI status is _not_ necessarily an error. > 252 */ > 253 blk_execute_rq(q, bd_disk, rq, 0); > 254 > 255 hdr->duration = jiffies_to_msecs(jiffies - start_time); > 256 > 257 return blk_complete_sghdr_rq(rq, hdr, bio); > > > > -- > Regards, > Peter Teoh > -- Regards, Peter Teoh -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
