Messages in this thread | | | Date | Sun, 3 Nov 2002 14:48:09 -0800 (PST) | From | Linus Torvalds <> | Subject | Re: swsusp: don't eat ide disks |
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On Sun, 3 Nov 2002, Pavel Machek wrote: > > How do I quiesce a queue? Is it ll_rw_blk stuff?
Just send a request down the request list, and make sure that
- the command is marked as being non-mergeable or re-orderable by software (as all special commands are)
- the command is not re-orderable / mergeable by hardware (and since the command in question would be something like "flush" or "spindown", hardware really would be quite broken if it re-ordered it ;)
and then just wait for its completion.
The code is not that complicated, it looks roughly something like
struct request *rq;
rq = blk_get_request(q, WRITE, __GFP_WAIT); rq->flags = REQ_BLOCK_PC; rq->data = NULL; rq->data_len = 0; rq->timeout = 5*HZ; /* Or whatever */ memset(rq->cmd, 0, sizeof(rq->cmd)); rq->cmd[0] = SYNCHRONIZE_CACHE; .. fill in whatever bytes the SYNCHRONIZE_CACHE cmd needs .. rq->cmd_len = 10; err = blk_do_rq(q, bdev, rq); blk_put_request(rq);
and you're done. The above should work pretty much on all block drivers out there, btw: the ones that don't understand SCSI commands should just ignore requests that aren't the regular REQ_CMD commands.
See drivers/block/scsi_ioctl.c for other examples of sending down commands to block devices.
Linus
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