How to setup a buffer_head in a driver

[Brian Kelly <bkelly@sulaco.com>]

Hi,
I'm writing a device driver that among other things needs to write data,
manufactured by the driver itself, to a block device.

I have this data in block sized kmalloc()'d chunks. So what I'm doing is
allocating a struct buffer_head, initialising it, fill out it's various
fields and send it to generic_make_request(). Something like the following
[inspired by looking at various drivers like loop and ram]:

	do {
		if((bh = kmem_cache_alloc(bh_cachep, SLAB_NOIO)) != NULL){
			break;
		}
		run_task_queue(&tq_disk);
		schedule_timeout(HZ);
	} while (1);

	memset(bh, 0, sizeof(*bh));

	bh->b_size = size;
	bh->b_dev = dev;
	bh->b_rdev = dev;
	bh->b_data = data;
	init_waitqueue_head(&bh->b_wait);
	bh->b_rsector = sect;
	bh->b_end_io = write_done;
	bh->b_private = NULL;
	generic_make_request(WRITE, bh);


Now this causes a panic in ll_rw_blk.c because the b_state isn't set
correctly. I experimented with this a little but decided I needed some
proper direction on this whole endeavour.

Soooo, what do I really need to do? What's the correct way to do what I want
to do or could someone point me at an existing driver that does this
sort of thing.

Thanks,

Brian
-- 
bkelly@sulaco.com