patch-2.3.99-pre1 linux/Documentation/sound/Maestro

• Lines: 44
• Date: Sun Mar 12 19:39:47 2000
• Orig file: v2.3.51/linux/Documentation/sound/Maestro
• Orig date: Fri Mar 10 16:40:38 2000

diff -u --recursive --new-file v2.3.51/linux/Documentation/sound/Maestro linux/Documentation/sound/Maestro
@@ -24,7 +24,7 @@
 
 The various families of Maestro are mostly identical as far as this 
 driver is concerned.  It doesn't touch the DSP parts that differ (though
-it could for FM synthesis)
+it could for FM synthesis).
 
 Driver OSS Behavior
 --------------------
@@ -90,8 +90,33 @@
 ( dsps_order=2 ).  These devices act as fully distinct units and use
 separate channels in the maestro.
 
+Power Management
+----------------
+
+As of version 0.14, this driver has a minimal understanding of PCI
+Power Management.  If it finds a valid power management capability
+on the PCI device it will attempt to use the power management
+functions of the maestro.  It will only do this on Maestro 2Es and
+only on machines that are known to function well.  You can
+force the use of power management by setting the 'use_pm' module
+option to 1, or can disable it entirely by setting it to 0.
+
+When using power management, the driver does a few things
+differently.  It will keep the chip in a lower power mode
+when the module is inserted but /dev/dsp is not open.  This
+allows the mixer to function but turns off the clocks
+on other parts of the chip.  When /dev/dsp is opened the chip
+is brought into full power mode, and brought back down
+when it is closed.  It also powers down the chip entirely
+when the module is removed or the machine is shutdown.  This
+can have nonobvious consequences.  CD audio may not work
+after a power managing driver is removed.  Also, software that
+doesn't understand power management may not be able to talk
+to the powered down chip until the machine goes through a hard
+reboot to bring it back.
+
 .. more details ..
------------------
+------------------
 
 drivers/sound/maestro.c contains comments that hopefully explain
 the maestro implementation.