diff options
Diffstat (limited to 'Documentation/scsi/libsas.txt')
| -rw-r--r-- | Documentation/scsi/libsas.txt | 82 |
1 files changed, 4 insertions, 78 deletions
diff --git a/Documentation/scsi/libsas.txt b/Documentation/scsi/libsas.txt index 3cc9c78..8cac649 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 -1. - (2) SAS 1.1 does not define I_T Nexus Reset TMF. Events @@ -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 -(DBMS). - -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 -lldd_execute_task(). - -You really want to set this to something (much) larger than -1. - -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 |
