patch-2.3.13 linux/drivers/scsi/README.st

• Lines: 112
• Date: Mon Aug 9 10:23:42 1999
• Orig file: v2.3.12/linux/drivers/scsi/README.st
• Orig date: Sat May 22 14:50:07 1999

diff -u --recursive --new-file v2.3.12/linux/drivers/scsi/README.st linux/drivers/scsi/README.st
@@ -2,7 +2,7 @@
 The driver is currently maintained by Kai M{kisara (email
 Kai.Makisara@metla.fi)
 
-Last modified: Sun Apr 18 13:24:43 1999 by makisara@home
+Last modified: Sat Aug  7 13:52:16 1999 by makisara@kai.makisara.local
 
 
 BASICS
@@ -130,22 +130,26 @@
 2^n * (page size). Because of this the actual buffer size may be
 larger than the buffer size specified with ST_BUFFER_BLOCKS.
 
-Allocation of the buffers is done at run-time when they are
-needed. Allocation of the specified number of buffers can be done at
-initialization if ST_RUNTIME_BUFFERS is defined non-zero. The
-advantage of run-time allocation is that memory is not wasted for
-buffers not being used. The disadvantage is that there may not be
-memory available at the time when a buffer is needed for the first
-time (once a buffer is allocated, it is not released).
-
-The maximum number of buffers allocated at initialization is defined by
-ST_MAX_BUFFERS. One buffer is allocated for each drive detected when
-the driver is initialized up to the maximum. The minimum number of
-allocated buffers is ST_EXTRA_DEVS (in hosts.h). This ensures some
-functionality also for the drives found after tape driver
-initialization (a SCSI adapter driver is loaded as a module). The
-default for ST_EXTRA_DEVS is two. The driver tries to allocate new
-buffers at run-time if necessary.
+A small number of buffers are allocated at driver initialisation. The
+maximum number of these buffers is defined by ST_MAX_BUFFERS. The
+maximum can be changed with kernel or module startup options. One
+buffer is allocated for each drive detected when the driver is
+initialized up to the maximum. The minimum number of allocated buffers
+is ST_EXTRA_DEVS (in hosts.h) (unless this number exceeds the defined
+maximum). This ensures some functionality also for the drives found
+after tape driver initialization (a SCSI adapter driver is loaded as a
+module). The default for ST_EXTRA_DEVS is two.
+
+The driver tries to allocate new buffers at run-time if
+necessary. These buffers are freed after use. If the maximum number of
+initial buffers is set to zero, all buffer allocation is done at
+run-time. The advantage of run-time allocation is that memory is not
+wasted for buffers not being used. The disadvantage is that there may
+not be memory available at the time when a buffer is needed for the
+first time (once a buffer is allocated, it is not released). This risk
+should not be big if the tape drive is connected to a PCI adapter that
+supports scatter/gather (the allocation is not limited to "DMA memory"
+and the buffer can be composed of several fragments).
 
 The threshold for triggering asynchronous write in fixed block mode
 is defined by ST_WRITE_THRESHOLD. This may be optimized for each
@@ -178,31 +182,43 @@
 extending the buffer will always fail.
 
 
-BOOT TIME CONFIGURATION
+MODULE PARAMETERS
 
 The buffer size, write threshold, and the maximum number of allocated buffers
-are configurable at boot time using, e.g., the LILO command line. The option
-syntax is the following:
+are configurable when the driver is loaded as a module. The keywords are:
+
+buffer_kbs=xxx             the buffer size in kilobytes is set to xxx
+write_threshold_kbs=xxx    the write threshold in kilobytes set to xxx
+max_buffers=xxx            the maximum number of tape buffer set to xxx
+max_sg_segs=xxx		   the maximum number of scatter/gather
+			   segments
+
+Note that if the buffer size is changed but the write threshold is not
+set, the write threshold is set to the new buffer size - 2 kB.
+
+
+BOOT TIME CONFIGURATION
+
+If the driver is compiled into the kernel, the same parameters can be
+also set using, e.g., the LILO command line. The preferred syntax is
+to use the same keywords as when loading the driver as module. If
+several parameters are set, the keyword-value pairs are separated with
+a comma (no spaces allowed). A colon can be used instead of the equal
+mark. The definition is prepended by the string st=. Here is an
+example:
 
-           st=aa[,bb[,cc]]
+	st=buffer_kbs:64,max_buffers:2
+
+The following syntax used by the old kernel versions is also supported:
+
+           st=aa[,bb[,cc[,dd]]]
 
 where
   aa is the buffer size in 1024 byte units
   bb is the write threshold in 1024 byte units
   cc is the maximum number of tape buffers to allocate (the number of
         buffers is bounded also by the number of drives detected)
-
-
-MODULE PARAMETERS
-
-The same parameters can be also set when the driver is loaded as a
-module. The keywords are:
-
-buffer_kbs=xxx             the buffer size in kilobytes is set to xxx
-write_threshold_kbs=xxx    the write threshold in kilobytes set to xxx
-max_buffers=xxx            the maximum number of tape buffer set to xxx
-max_sg_segs=xxx		   the maximum number of scatter/gather
-			   segments
+  dd is the maximum number of scatter/gather segments
 
 
 IOCTLS