How to setup a buffer_head in a driver

From: Brian Kelly (bkelly@sulaco.com)
Date: Tue Jan 14 2003 - 17:35:45 EST

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
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This archive was generated by hypermail 2b29 : Wed Jan 15 2003 - 22:00:52 EST