1What:		/sys/firmware/acpi/bgrt/
2Date:		January 2012
3Contact:	Matthew Garrett <mjg@redhat.com>
4Description:
5		The BGRT is an ACPI 5.0 feature that allows the OS
6		to obtain a copy of the firmware boot splash and
7		some associated metadata. This is intended to be used
8		by boot splash applications in order to interact with
9		the firmware boot splash in order to avoid jarring
10		transitions.
11
12		image: The image bitmap. Currently a 32-bit BMP.
13		status: 1 if the image is valid, 0 if firmware invalidated it.
14		type: 0 indicates image is in BMP format.
15		version: The version of the BGRT. Currently 1.
16		xoffset: The number of pixels between the left of the screen
17			 and the left edge of the image.
18		yoffset: The number of pixels between the top of the screen
19			 and the top edge of the image.
20
21What:		/sys/firmware/acpi/interrupts/
22Date:		February 2008
23Contact:	Len Brown <lenb@kernel.org>
24Description:
25		All ACPI interrupts are handled via a single IRQ,
26		the System Control Interrupt (SCI), which appears
27		as "acpi" in /proc/interrupts.
28
29		However, one of the main functions of ACPI is to make
30		the platform understand random hardware without
31		special driver support.  So while the SCI handles a few
32		well known (fixed feature) interrupts sources, such
33		as the power button, it can also handle a variable
34		number of a "General Purpose Events" (GPE).
35
36		A GPE vectors to a specified handler in AML, which
37		can do a anything the BIOS writer wants from
38		OS context.  GPE 0x12, for example, would vector
39		to a level or edge handler called _L12 or _E12.
40		The handler may do its business and return.
41		Or the handler may send send a Notify event
42		to a Linux device driver registered on an ACPI device,
43		such as a battery, or a processor.
44
45		To figure out where all the SCI's are coming from,
46		/sys/firmware/acpi/interrupts contains a file listing
47		every possible source, and the count of how many
48		times it has triggered.
49
50		$ cd /sys/firmware/acpi/interrupts
51		$ grep . *
52		error:	     0
53		ff_gbl_lock:	   0   enable
54		ff_pmtimer:	  0  invalid
55		ff_pwr_btn:	  0   enable
56		ff_rt_clk:	 2  disable
57		ff_slp_btn:	  0  invalid
58		gpe00:	     0	invalid
59		gpe01:	     0	 enable
60		gpe02:	   108	 enable
61		gpe03:	     0	invalid
62		gpe04:	     0	invalid
63		gpe05:	     0	invalid
64		gpe06:	     0	 enable
65		gpe07:	     0	 enable
66		gpe08:	     0	invalid
67		gpe09:	     0	invalid
68		gpe0A:	     0	invalid
69		gpe0B:	     0	invalid
70		gpe0C:	     0	invalid
71		gpe0D:	     0	invalid
72		gpe0E:	     0	invalid
73		gpe0F:	     0	invalid
74		gpe10:	     0	invalid
75		gpe11:	     0	invalid
76		gpe12:	     0	invalid
77		gpe13:	     0	invalid
78		gpe14:	     0	invalid
79		gpe15:	     0	invalid
80		gpe16:	     0	invalid
81		gpe17:	  1084	 enable
82		gpe18:	     0	 enable
83		gpe19:	     0	invalid
84		gpe1A:	     0	invalid
85		gpe1B:	     0	invalid
86		gpe1C:	     0	invalid
87		gpe1D:	     0	invalid
88		gpe1E:	     0	invalid
89		gpe1F:	     0	invalid
90		gpe_all:    1192
91		sci:	1194
92		sci_not:     0
93
94		sci - The number of times the ACPI SCI
95		has been called and claimed an interrupt.
96
97		sci_not - The number of times the ACPI SCI
98		has been called and NOT claimed an interrupt.
99
100		gpe_all - count of SCI caused by GPEs.
101
102		gpeXX - count for individual GPE source
103
104		ff_gbl_lock - Global Lock
105
106		ff_pmtimer - PM Timer
107
108		ff_pwr_btn - Power Button
109
110		ff_rt_clk - Real Time Clock
111
112		ff_slp_btn - Sleep Button
113
114		error - an interrupt that can't be accounted for above.
115
116		invalid: it's either a GPE or a Fixed Event that
117			doesn't have an event handler.
118
119		disable: the GPE/Fixed Event is valid but disabled.
120
121		enable: the GPE/Fixed Event is valid and enabled.
122
123		Root has permission to clear any of these counters.  Eg.
124		# echo 0 > gpe11
125
126		All counters can be cleared by clearing the total "sci":
127		# echo 0 > sci
128
129		None of these counters has an effect on the function
130		of the system, they are simply statistics.
131
132		Besides this, user can also write specific strings to these files
133		to enable/disable/clear ACPI interrupts in user space, which can be
134		used to debug some ACPI interrupt storm issues.
135
136		Note that only writting to VALID GPE/Fixed Event is allowed,
137		i.e. user can only change the status of runtime GPE and
138		Fixed Event with event handler installed.
139
140		Let's take power button fixed event for example, please kill acpid
141		and other user space applications so that the machine won't shutdown
142		when pressing the power button.
143		# cat ff_pwr_btn
144		0	enabled
145		# press the power button for 3 times;
146		# cat ff_pwr_btn
147		3	enabled
148		# echo disable > ff_pwr_btn
149		# cat ff_pwr_btn
150		3	disabled
151		# press the power button for 3 times;
152		# cat ff_pwr_btn
153		3	disabled
154		# echo enable > ff_pwr_btn
155		# cat ff_pwr_btn
156		4	enabled
157		/*
158		 * this is because the status bit is set even if the enable bit is cleared,
159		 * and it triggers an ACPI fixed event when the enable bit is set again
160		 */
161		# press the power button for 3 times;
162		# cat ff_pwr_btn
163		7	enabled
164		# echo disable > ff_pwr_btn
165		# press the power button for 3 times;
166		# echo clear > ff_pwr_btn	/* clear the status bit */
167		# echo disable > ff_pwr_btn
168		# cat ff_pwr_btn
169		7	enabled
170
171