path: root/Documentation/scsi/libsas.txt
diff options
Diffstat (limited to 'Documentation/scsi/libsas.txt')
1 files changed, 4 insertions, 78 deletions
diff --git a/Documentation/scsi/libsas.txt b/Documentation/scsi/libsas.txt
index 3cc9c7843e15..8cac6492aade 100644
--- a/Documentation/scsi/libsas.txt
+++ b/Documentation/scsi/libsas.txt
@@ -226,9 +226,6 @@ static int register_sas_ha(struct my_sas_ha *my_ha)
my_ha->sas_ha.lldd_dev_found = my_dev_found;
my_ha->sas_ha.lldd_dev_gone = my_dev_gone;
- my_ha->sas_ha.lldd_max_execute_num = lldd_max_execute_num; (1)
- my_ha->sas_ha.lldd_queue_size = ha_can_queue;
my_ha->sas_ha.lldd_execute_task = my_execute_task;
my_ha->sas_ha.lldd_abort_task = my_abort_task;
@@ -247,28 +244,6 @@ static int register_sas_ha(struct my_sas_ha *my_ha)
return sas_register_ha(&my_ha->sas_ha);
-(1) This is normally a LLDD parameter, something of the
-lines of a task collector. What it tells the SAS Layer is
-whether the SAS layer should run in Direct Mode (default:
-value 0 or 1) or Task Collector Mode (value greater than 1).
-In Direct Mode, the SAS Layer calls Execute Task as soon as
-it has a command to send to the SDS, _and_ this is a single
-command, i.e. not linked.
-Some hardware (e.g. aic94xx) has the capability to DMA more
-than one task at a time (interrupt) from host memory. Task
-Collector Mode is an optional feature for HAs which support
-this in their hardware. (Again, it is completely optional
-even if your hardware supports it.)
-In Task Collector Mode, the SAS Layer would do _natural_
-coalescing of tasks and at the appropriate moment it would
-call your driver to DMA more than one task in a single HA
-interrupt. DMBS may want to use this by insmod/modprobe
-setting the lldd_max_execute_num to something greater than
(2) SAS 1.1 does not define I_T Nexus Reset TMF.
@@ -325,71 +300,22 @@ PHYE_SPINUP_HOLD -- SATA is present, COMWAKE not sent.
The Execute Command SCSI RPC:
- int (*lldd_execute_task)(struct sas_task *, int num,
- unsigned long gfp_flags);
+ int (*lldd_execute_task)(struct sas_task *, gfp_t gfp_flags);
-Used to queue a task to the SAS LLDD. @task is the tasks to
-be executed. @num should be the number of tasks being
-queued at this function call (they are linked listed via
-task::list), @gfp_mask should be the gfp_mask defining the
-context of the caller.
+Used to queue a task to the SAS LLDD. @task is the task to be executed.
+@gfp_mask is the gfp_mask defining the context of the caller.
This function should implement the Execute Command SCSI RPC,
-or if you're sending a SCSI Task as linked commands, you
-should also use this function.
-That is, when lldd_execute_task() is called, the command(s)
+That is, when lldd_execute_task() is called, the command
go out on the transport *immediately*. There is *no*
queuing of any sort and at any level in a SAS LLDD.
-The use of task::list is two-fold, one for linked commands,
-the other discussed below.
-It is possible to queue up more than one task at a time, by
-initializing the list element of struct sas_task, and
-passing the number of tasks enlisted in this manner in num.
Returns: -SAS_QUEUE_FULL, -ENOMEM, nothing was queued;
0, the task(s) were queued.
-If you want to pass num > 1, then either
-A) you're the only caller of this function and keep track
- of what you've queued to the LLDD, or
-B) you know what you're doing and have a strategy of
- retrying.
-As opposed to queuing one task at a time (function call),
-batch queuing of tasks, by having num > 1, greatly
-simplifies LLDD code, sequencer code, and _hardware design_,
-and has some performance advantages in certain situations
-The LLDD advertises if it can take more than one command at
-a time at lldd_execute_task(), by setting the
-lldd_max_execute_num parameter (controlled by "collector"
-module parameter in aic94xx SAS LLDD).
-You should leave this to the default 1, unless you know what
-you're doing.
-This is a function of the LLDD, to which the SAS layer can
-cater to.
-int lldd_queue_size
- The host adapter's queue size. This is the maximum
-number of commands the lldd can have pending to domain
-devices on behalf of all upper layers submitting through
-You really want to set this to something (much) larger than
-This _really_ has absolutely nothing to do with queuing.
-There is no queuing in SAS LLDDs.
struct sas_task {
dev -- the device this task is destined to
- list -- must be initialized (INIT_LIST_HEAD)
task_proto -- _one_ of enum sas_proto
scatter -- pointer to scatter gather list array
num_scatter -- number of elements in scatter