aboutsummaryrefslogtreecommitdiff
path: root/Documentation
diff options
context:
space:
mode:
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/00-INDEX2
-rw-r--r--Documentation/blackfin/kgdb.txt155
-rw-r--r--Documentation/feature-removal-schedule.txt8
-rw-r--r--Documentation/filesystems/ext4.txt5
-rw-r--r--Documentation/filesystems/proc.txt7
-rw-r--r--Documentation/kernel-parameters.txt26
-rw-r--r--Documentation/sound/alsa/DocBook/writing-an-alsa-driver.tmpl3
-rw-r--r--Documentation/sparc/sbus_drivers.txt309
-rw-r--r--Documentation/timers/00-INDEX10
-rw-r--r--Documentation/timers/hpet.txt (renamed from Documentation/hpet.txt)43
10 files changed, 62 insertions, 506 deletions
diff --git a/Documentation/00-INDEX b/Documentation/00-INDEX
index 73060819ed9..43827780010 100644
--- a/Documentation/00-INDEX
+++ b/Documentation/00-INDEX
@@ -159,8 +159,6 @@ hayes-esp.txt
- info on using the Hayes ESP serial driver.
highuid.txt
- notes on the change from 16 bit to 32 bit user/group IDs.
-hpet.txt
- - High Precision Event Timer Driver for Linux.
timers/
- info on the timer related topics
hw_random.txt
diff --git a/Documentation/blackfin/kgdb.txt b/Documentation/blackfin/kgdb.txt
deleted file mode 100644
index 84f6a484ae9..00000000000
--- a/Documentation/blackfin/kgdb.txt
+++ /dev/null
@@ -1,155 +0,0 @@
- A Simple Guide to Configure KGDB
-
- Sonic Zhang <sonic.zhang@analog.com>
- Aug. 24th 2006
-
-
-This KGDB patch enables the kernel developer to do source level debugging on
-the kernel for the Blackfin architecture. The debugging works over either the
-ethernet interface or one of the uarts. Both software breakpoints and
-hardware breakpoints are supported in this version.
-http://docs.blackfin.uclinux.org/doku.php?id=kgdb
-
-
-2 known issues:
-1. This bug:
- http://blackfin.uclinux.org/tracker/index.php?func=detail&aid=544&group_id=18&atid=145
- The GDB client for Blackfin uClinux causes incorrect values of local
- variables to be displayed when the user breaks the running of kernel in GDB.
-2. Because of a hardware bug in Blackfin 533 v1.0.3:
- 05000067 - Watchpoints (Hardware Breakpoints) are not supported
- Hardware breakpoints cannot be set properly.
-
-
-Debug over Ethernet:
-
-1. Compile and install the cross platform version of gdb for blackfin, which
- can be found at $(BINROOT)/bfin-elf-gdb.
-
-2. Apply this patch to the 2.6.x kernel. Select the menuconfig option under
- "Kernel hacking" -> "Kernel debugging" -> "KGDB: kernel debug with remote gdb".
- With this selected, option "Full Symbolic/Source Debugging support" and
- "Compile the kernel with frame pointers" are also selected.
-
-3. Select option "KGDB: connect over (Ethernet)". Add "kgdboe=@target-IP/,@host-IP/" to
- the option "Compiled-in Kernel Boot Parameter" under "Kernel hacking".
-
-4. Connect minicom to the serial port and boot the kernel image.
-
-5. Configure the IP "/> ifconfig eth0 target-IP"
-
-6. Start GDB client "bfin-elf-gdb vmlinux".
-
-7. Connect to the target "(gdb) target remote udp:target-IP:6443".
-
-8. Set software breakpoint "(gdb) break sys_open".
-
-9. Continue "(gdb) c".
-
-10. Run ls in the target console "/> ls".
-
-11. Breakpoint hits. "Breakpoint 1: sys_open(..."
-
-12. Display local variables and function paramters.
- (*) This operation gives wrong results, see known issue 1.
-
-13. Single stepping "(gdb) si".
-
-14. Remove breakpoint 1. "(gdb) del 1"
-
-15. Set hardware breakpoint "(gdb) hbreak sys_open".
-
-16. Continue "(gdb) c".
-
-17. Run ls in the target console "/> ls".
-
-18. Hardware breakpoint hits. "Breakpoint 1: sys_open(...".
- (*) This hardware breakpoint will not be hit, see known issue 2.
-
-19. Continue "(gdb) c".
-
-20. Interrupt the target in GDB "Ctrl+C".
-
-21. Detach from the target "(gdb) detach".
-
-22. Exit GDB "(gdb) quit".
-
-
-Debug over the UART:
-
-1. Compile and install the cross platform version of gdb for blackfin, which
- can be found at $(BINROOT)/bfin-elf-gdb.
-
-2. Apply this patch to the 2.6.x kernel. Select the menuconfig option under
- "Kernel hacking" -> "Kernel debugging" -> "KGDB: kernel debug with remote gdb".
- With this selected, option "Full Symbolic/Source Debugging support" and
- "Compile the kernel with frame pointers" are also selected.
-
-3. Select option "KGDB: connect over (UART)". Set "KGDB: UART port number" to be
- a different one from the console. Don't forget to change the mode of
- blackfin serial driver to PIO. Otherwise kgdb works incorrectly on UART.
-
-4. If you want connect to kgdb when the kernel boots, enable
- "KGDB: Wait for gdb connection early"
-
-5. Compile kernel.
-
-6. Connect minicom to the serial port of the console and boot the kernel image.
-
-7. Start GDB client "bfin-elf-gdb vmlinux".
-
-8. Set the baud rate in GDB "(gdb) set remotebaud 57600".
-
-9. Connect to the target on the second serial port "(gdb) target remote /dev/ttyS1".
-
-10. Set software breakpoint "(gdb) break sys_open".
-
-11. Continue "(gdb) c".
-
-12. Run ls in the target console "/> ls".
-
-13. A breakpoint is hit. "Breakpoint 1: sys_open(..."
-
-14. All other operations are the same as that in KGDB over Ethernet.
-
-
-Debug over the same UART as console:
-
-1. Compile and install the cross platform version of gdb for blackfin, which
- can be found at $(BINROOT)/bfin-elf-gdb.
-
-2. Apply this patch to the 2.6.x kernel. Select the menuconfig option under
- "Kernel hacking" -> "Kernel debugging" -> "KGDB: kernel debug with remote gdb".
- With this selected, option "Full Symbolic/Source Debugging support" and
- "Compile the kernel with frame pointers" are also selected.
-
-3. Select option "KGDB: connect over UART". Set "KGDB: UART port number" to console.
- Don't forget to change the mode of blackfin serial driver to PIO.
- Otherwise kgdb works incorrectly on UART.
-
-4. If you want connect to kgdb when the kernel boots, enable
- "KGDB: Wait for gdb connection early"
-
-5. Connect minicom to the serial port and boot the kernel image.
-
-6. (Optional) Ask target to wait for gdb connection by entering Ctrl+A. In minicom, you should enter Ctrl+A+A.
-
-7. Start GDB client "bfin-elf-gdb vmlinux".
-
-8. Set the baud rate in GDB "(gdb) set remotebaud 57600".
-
-9. Connect to the target "(gdb) target remote /dev/ttyS0".
-
-10. Set software breakpoint "(gdb) break sys_open".
-
-11. Continue "(gdb) c". Then enter Ctrl+C twice to stop GDB connection.
-
-12. Run ls in the target console "/> ls". Dummy string can be seen on the console.
-
-13. Then connect the gdb to target again. "(gdb) target remote /dev/ttyS0".
- Now you will find a breakpoint is hit. "Breakpoint 1: sys_open(..."
-
-14. All other operations are the same as that in KGDB over Ethernet. The only
- difference is that after continue command in GDB, please stop GDB
- connection by 2 "Ctrl+C"s and connect again after breakpoints are hit or
- Ctrl+A is entered.
diff --git a/Documentation/feature-removal-schedule.txt b/Documentation/feature-removal-schedule.txt
index 3d2d0c29f02..cc8093c15cf 100644
--- a/Documentation/feature-removal-schedule.txt
+++ b/Documentation/feature-removal-schedule.txt
@@ -287,14 +287,6 @@ Who: Glauber Costa <gcosta@redhat.com>
---------------------------
-What: old style serial driver for ColdFire (CONFIG_SERIAL_COLDFIRE)
-When: 2.6.28
-Why: This driver still uses the old interface and has been replaced
- by CONFIG_SERIAL_MCF.
-Who: Sebastian Siewior <sebastian@breakpoint.cc>
-
----------------------------
-
What: /sys/o2cb symlink
When: January 2010
Why: /sys/fs/o2cb is the proper location for this information - /sys/o2cb
diff --git a/Documentation/filesystems/ext4.txt b/Documentation/filesystems/ext4.txt
index 74484e69640..eb154ef36c2 100644
--- a/Documentation/filesystems/ext4.txt
+++ b/Documentation/filesystems/ext4.txt
@@ -223,6 +223,11 @@ errors=remount-ro(*) Remount the filesystem read-only on an error.
errors=continue Keep going on a filesystem error.
errors=panic Panic and halt the machine if an error occurs.
+data_err=ignore(*) Just print an error message if an error occurs
+ in a file data buffer in ordered mode.
+data_err=abort Abort the journal if an error occurs in a file
+ data buffer in ordered mode.
+
grpid Give objects the same group ID as their creator.
bsdgroups
diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index d831d24d2a6..b488edad743 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -1331,13 +1331,6 @@ determine whether or not they are still functioning properly.
Because the NMI watchdog shares registers with oprofile, by disabling the NMI
watchdog, oprofile may have more registers to utilize.
-maps_protect
-------------
-
-Enables/Disables the protection of the per-process proc entries "maps" and
-"smaps". When enabled, the contents of these files are visible only to
-readers that are allowed to ptrace() the given process.
-
msgmni
------
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 25efbaf1f59..2443f5bb436 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -658,11 +658,12 @@ and is between 256 and 4096 characters. It is defined in the file
earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
earlyprintk=vga
earlyprintk=serial[,ttySn[,baudrate]]
+ earlyprintk=dbgp
Append ",keep" to not disable it when the real console
takes over.
- Only vga or serial at a time, not both.
+ Only vga or serial or usb debug port at a time.
Currently only ttyS0 and ttyS1 are supported.
@@ -1231,6 +1232,29 @@ and is between 256 and 4096 characters. It is defined in the file
or
memmap=0x10000$0x18690000
+ memory_corruption_check=0/1 [X86]
+ Some BIOSes seem to corrupt the first 64k of
+ memory when doing things like suspend/resume.
+ Setting this option will scan the memory
+ looking for corruption. Enabling this will
+ both detect corruption and prevent the kernel
+ from using the memory being corrupted.
+ However, its intended as a diagnostic tool; if
+ repeatable BIOS-originated corruption always
+ affects the same memory, you can use memmap=
+ to prevent the kernel from using that memory.
+
+ memory_corruption_check_size=size [X86]
+ By default it checks for corruption in the low
+ 64k, making this memory unavailable for normal
+ use. Use this parameter to scan for
+ corruption in more or less memory.
+
+ memory_corruption_check_period=seconds [X86]
+ By default it checks for corruption every 60
+ seconds. Use this parameter to check at some
+ other rate. 0 disables periodic checking.
+
memtest= [KNL,X86] Enable memtest
Format: <integer>
range: 0,4 : pattern number
diff --git a/Documentation/sound/alsa/DocBook/writing-an-alsa-driver.tmpl b/Documentation/sound/alsa/DocBook/writing-an-alsa-driver.tmpl
index b54cb5048df..87a7c07ab65 100644
--- a/Documentation/sound/alsa/DocBook/writing-an-alsa-driver.tmpl
+++ b/Documentation/sound/alsa/DocBook/writing-an-alsa-driver.tmpl
@@ -5073,8 +5073,7 @@ struct _snd_pcm_runtime {
with <constant>SNDRV_DMA_TYPE_CONTINUOUS</constant> type and the
<function>snd_dma_continuous_data(GFP_KERNEL)</function> device pointer,
where <constant>GFP_KERNEL</constant> is the kernel allocation flag to
- use. For the SBUS, <constant>SNDRV_DMA_TYPE_SBUS</constant> and
- <function>snd_dma_sbus_data(sbus_dev)</function> are used instead.
+ use.
For the PCI scatter-gather buffers, use
<constant>SNDRV_DMA_TYPE_DEV_SG</constant> with
<function>snd_dma_pci_data(pci)</function>
diff --git a/Documentation/sparc/sbus_drivers.txt b/Documentation/sparc/sbus_drivers.txt
deleted file mode 100644
index eb1e28ad882..00000000000
--- a/Documentation/sparc/sbus_drivers.txt
+++ /dev/null
@@ -1,309 +0,0 @@
-
- Writing SBUS Drivers
-
- David S. Miller (davem@redhat.com)
-
- The SBUS driver interfaces of the Linux kernel have been
-revamped completely for 2.4.x for several reasons. Foremost were
-performance and complexity concerns. This document details these
-new interfaces and how they are used to write an SBUS device driver.
-
- SBUS drivers need to include <asm/sbus.h> to get access
-to functions and structures described here.
-
- Probing and Detection
-
- Each SBUS device inside the machine is described by a
-structure called "struct sbus_dev". Likewise, each SBUS bus
-found in the system is described by a "struct sbus_bus". For
-each SBUS bus, the devices underneath are hung in a tree-like
-fashion off of the bus structure.
-
- The SBUS device structure contains enough information
-for you to implement your device probing algorithm and obtain
-the bits necessary to run your device. The most commonly
-used members of this structure, and their typical usage,
-will be detailed below.
-
- Here is a piece of skeleton code for performing a device
-probe in an SBUS driver under Linux:
-
- static int __devinit mydevice_probe_one(struct sbus_dev *sdev)
- {
- struct mysdevice *mp = kzalloc(sizeof(*mp), GFP_KERNEL);
-
- if (!mp)
- return -ENODEV;
-
- ...
- dev_set_drvdata(&sdev->ofdev.dev, mp);
- return 0;
- ...
- }
-
- static int __devinit mydevice_probe(struct of_device *dev,
- const struct of_device_id *match)
- {
- struct sbus_dev *sdev = to_sbus_device(&dev->dev);
-
- return mydevice_probe_one(sdev);
- }
-
- static int __devexit mydevice_remove(struct of_device *dev)
- {
- struct sbus_dev *sdev = to_sbus_device(&dev->dev);
- struct mydevice *mp = dev_get_drvdata(&dev->dev);
-
- return mydevice_remove_one(sdev, mp);
- }
-
- static struct of_device_id mydevice_match[] = {
- {
- .name = "mydevice",
- },
- {},
- };
-
- MODULE_DEVICE_TABLE(of, mydevice_match);
-
- static struct of_platform_driver mydevice_driver = {
- .match_table = mydevice_match,
- .probe = mydevice_probe,
- .remove = __devexit_p(mydevice_remove),
- .driver = {
- .name = "mydevice",
- },
- };
-
- static int __init mydevice_init(void)
- {
- return of_register_driver(&mydevice_driver, &sbus_bus_type);
- }
-
- static void __exit mydevice_exit(void)
- {
- of_unregister_driver(&mydevice_driver);
- }
-
- module_init(mydevice_init);
- module_exit(mydevice_exit);
-
- The mydevice_match table is a series of entries which
-describes what SBUS devices your driver is meant for. In the
-simplest case you specify a string for the 'name' field. Every
-SBUS device with a 'name' property matching your string will
-be passed one-by-one to your .probe method.
-
- You should store away your device private state structure
-pointer in the drvdata area so that you can retrieve it later on
-in your .remove method.
-
- Any memory allocated, registers mapped, IRQs registered,
-etc. must be undone by your .remove method so that all resources
-of your device are released by the time it returns.
-
- You should _NOT_ use the for_each_sbus(), for_each_sbusdev(),
-and for_all_sbusdev() interfaces. They are deprecated, will be
-removed, and no new driver should reference them ever.
-
- Mapping and Accessing I/O Registers
-
- Each SBUS device structure contains an array of descriptors
-which describe each register set. We abuse struct resource for that.
-They each correspond to the "reg" properties provided by the OBP firmware.
-
- Before you can access your device's registers you must map
-them. And later if you wish to shutdown your driver (for module
-unload or similar) you must unmap them. You must treat them as
-a resource, which you allocate (map) before using and free up
-(unmap) when you are done with it.
-
- The mapping information is stored in an opaque value
-typed as an "unsigned long". This is the type of the return value
-of the mapping interface, and the arguments to the unmapping
-interface. Let's say you want to map the first set of registers.
-Perhaps part of your driver software state structure looks like:
-
- struct mydevice {
- unsigned long control_regs;
- ...
- struct sbus_dev *sdev;
- ...
- };
-
- At initialization time you then use the sbus_ioremap
-interface to map in your registers, like so:
-
- static void init_one_mydevice(struct sbus_dev *sdev)
- {
- struct mydevice *mp;
- ...
-
- mp->control_regs = sbus_ioremap(&sdev->resource[0], 0,
- CONTROL_REGS_SIZE, "mydevice regs");
- if (!mp->control_regs) {
- /* Failure, cleanup and return. */
- }
- }
-
- Second argument to sbus_ioremap is an offset for
-cranky devices with broken OBP PROM. The sbus_ioremap uses only
-a start address and flags from the resource structure.
-Therefore it is possible to use the same resource to map
-several sets of registers or even to fabricate a resource
-structure if driver gets physical address from some private place.
-This practice is discouraged though. Use whatever OBP PROM
-provided to you.
-
- And here is how you might unmap these registers later at
-driver shutdown or module unload time, using the sbus_iounmap
-interface:
-
- static void mydevice_unmap_regs(struct mydevice *mp)
- {
- sbus_iounmap(mp->control_regs, CONTROL_REGS_SIZE);
- }
-
- Finally, to actually access your registers there are 6
-interface routines at your disposal. Accesses are byte (8 bit),
-word (16 bit), or longword (32 bit) sized. Here they are:
-
- u8 sbus_readb(unsigned long reg) /* read byte */
- u16 sbus_readw(unsigned long reg) /* read word */
- u32 sbus_readl(unsigned long reg) /* read longword */
- void sbus_writeb(u8 value, unsigned long reg) /* write byte */
- void sbus_writew(u16 value, unsigned long reg) /* write word */
- void sbus_writel(u32 value, unsigned long reg) /* write longword */
-
- So, let's say your device has a control register of some sort
-at offset zero. The following might implement resetting your device:
-
- #define CONTROL 0x00UL
-
- #define CONTROL_RESET 0x00000001 /* Reset hardware */
-
- static void mydevice_reset(struct mydevice *mp)
- {
- sbus_writel(CONTROL_RESET, mp->regs + CONTROL);
- }
-
- Or perhaps there is a data port register at an offset of
-16 bytes which allows you to read bytes from a fifo in the device:
-
- #define DATA 0x10UL
-
- static u8 mydevice_get_byte(struct mydevice *mp)
- {
- return sbus_readb(mp->regs + DATA);
- }
-
- It's pretty straightforward, and clueful readers may have
-noticed that these interfaces mimick the PCI interfaces of the
-Linux kernel. This was not by accident.
-
- WARNING:
-
- DO NOT try to treat these opaque register mapping
- values as a memory mapped pointer to some structure
- which you can dereference.
-
- It may be memory mapped, it may not be. In fact it
- could be a physical address, or it could be the time
- of day xor'd with 0xdeadbeef. :-)
-
- Whatever it is, it's an implementation detail. The
- interface was done this way to shield the driver
- author from such complexities.
-
- Doing DVMA
-
- SBUS devices can perform DMA transactions in a way similar
-to PCI but dissimilar to ISA, e.g. DMA masters supply address.
-In contrast to PCI, however, that address (a bus address) is
-translated by IOMMU before a memory access is performed and therefore
-it is virtual. Sun calls this procedure DVMA.
-
- Linux supports two styles of using SBUS DVMA: "consistent memory"
-and "streaming DVMA". CPU view of consistent memory chunk is, well,
-consistent with a view of a device. Think of it as an uncached memory.
-Typically this way of doing DVMA is not very fast and drivers use it
-mostly for control blocks or queues. On some CPUs we cannot flush or
-invalidate individual pages or cache lines and doing explicit flushing
-over ever little byte in every control block would be wasteful.
-
-Streaming DVMA is a preferred way to transfer large amounts of data.
-This process works in the following way:
-1. a CPU stops accessing a certain part of memory,
- flushes its caches covering that memory;
-2. a device does DVMA accesses, then posts an interrupt;
-3. CPU invalidates its caches and starts to access the memory.
-
-A single streaming DVMA operation can touch several discontiguous
-regions of a virtual bus address space. This is called a scatter-gather
-DVMA.
-
-[TBD: Why do not we neither Solaris attempt to map disjoint pages
-into a single virtual chunk with the help of IOMMU, so that non SG
-DVMA masters would do SG? It'd be very helpful for RAID.]
-
- In order to perform a consistent DVMA a driver does something
-like the following:
-
- char *mem; /* Address in the CPU space */
- u32 busa; /* Address in the SBus space */
-
- mem = (char *) sbus_alloc_consistent(sdev, MYMEMSIZE, &busa);
-
- Then mem is used when CPU accesses this memory and u32
-is fed to the device so that it can do DVMA. This is typically
-done with an sbus_writel() into some device register.
-
- Do not forget to free the DVMA resources once you are done:
-
- sbus_free_consistent(sdev, MYMEMSIZE, mem, busa);
-
- Streaming DVMA is more interesting. First you allocate some
-memory suitable for it or pin down some user pages. Then it all works
-like this:
-
- char *mem = argumen1;
- unsigned int size = argument2;
- u32 busa; /* Address in the SBus space */
-
- *mem = 1; /* CPU can access */
- busa = sbus_map_single(sdev, mem, size);
- if (busa == 0) .......
-
- /* Tell the device to use busa here */
- /* CPU cannot access the memory without sbus_dma_sync_single() */
-
- sbus_unmap_single(sdev, busa, size);
- if (*mem == 0) .... /* CPU can access again */
-
- It is possible to retain mappings and ask the device to
-access data again and again without calling sbus_unmap_single.
-However, CPU caches must be invalidated with sbus_dma_sync_single
-before such access.
-
-[TBD but what about writeback caches here... do we have any?]
-
- There is an equivalent set of functions doing the same thing
-only with several memory segments at once for devices capable of
-scatter-gather transfers. Use the Source, Luke.
-
- Examples
-
- drivers/net/sunhme.c
- This is a complicated driver which illustrates many concepts
-discussed above and plus it handles both PCI and SBUS boards.
-
- drivers/scsi/esp.c
- Check it out for scatter-gather DVMA.
-
- drivers/sbus/char/bpp.c
- A non-DVMA device.
-
- drivers/net/sunlance.c
- Lance driver abuses consistent mappings for data transfer.
-It is a nifty trick which we do not particularly recommend...
-Just check it out and know that it's legal.
diff --git a/Documentation/timers/00-INDEX b/Documentation/timers/00-INDEX
new file mode 100644
index 00000000000..397dc35e132
--- /dev/null
+++ b/Documentation/timers/00-INDEX
@@ -0,0 +1,10 @@
+00-INDEX
+ - this file
+highres.txt
+ - High resolution timers and dynamic ticks design notes
+hpet.txt
+ - High Precision Event Timer Driver for Linux
+hrtimers.txt
+ - subsystem for high-resolution kernel timers
+timer_stats.txt
+ - timer usage statistics
diff --git a/Documentation/hpet.txt b/Documentation/timers/hpet.txt
index 6ad52d9dad6..e7c09abcfab 100644
--- a/Documentation/hpet.txt
+++ b/Documentation/timers/hpet.txt
@@ -1,21 +1,32 @@
High Precision Event Timer Driver for Linux
-The High Precision Event Timer (HPET) hardware is the future replacement
-for the 8254 and Real Time Clock (RTC) periodic timer functionality.
-Each HPET can have up to 32 timers. It is possible to configure the
-first two timers as legacy replacements for 8254 and RTC periodic timers.
-A specification done by Intel and Microsoft can be found at
-<http://www.intel.com/technology/architecture/hpetspec.htm>.
+The High Precision Event Timer (HPET) hardware follows a specification
+by Intel and Microsoft which can be found at
+
+ http://www.intel.com/technology/architecture/hpetspec.htm
+
+Each HPET has one fixed-rate counter (at 10+ MHz, hence "High Precision")
+and up to 32 comparators. Normally three or more comparators are provided,
+each of which can generate oneshot interupts and at least one of which has
+additional hardware to support periodic interrupts. The comparators are
+also called "timers", which can be misleading since usually timers are
+independent of each other ... these share a counter, complicating resets.
+
+HPET devices can support two interrupt routing modes. In one mode, the
+comparators are additional interrupt sources with no particular system
+role. Many x86 BIOS writers don't route HPET interrupts at all, which
+prevents use of that mode. They support the other "legacy replacement"
+mode where the first two comparators block interrupts from 8254 timers
+and from the RTC.
The driver supports detection of HPET driver allocation and initialization
of the HPET before the driver module_init routine is called. This enables
platform code which uses timer 0 or 1 as the main timer to intercept HPET
initialization. An example of this initialization can be found in
-arch/i386/kernel/time_hpet.c.
+arch/x86/kernel/hpet.c.
-The driver provides two APIs which are very similar to the API found in
-the rtc.c driver. There is a user space API and a kernel space API.
-An example user space program is provided below.
+The driver provides a userspace API which resembles the API found in the
+RTC driver framework. An example user space program is provided below.
#include <stdio.h>
#include <stdlib.h>
@@ -286,15 +297,3 @@ out:
return;
}
-
-The kernel API has three interfaces exported from the driver:
-
- hpet_register(struct hpet_task *tp, int periodic)
- hpet_unregister(struct hpet_task *tp)
- hpet_control(struct hpet_task *tp, unsigned int cmd, unsigned long arg)
-
-The kernel module using this interface fills in the ht_func and ht_data
-members of the hpet_task structure before calling hpet_register.
-hpet_control simply vectors to the hpet_ioctl routine and has the same
-commands and respective arguments as the user API. hpet_unregister
-is used to terminate usage of the HPET timer reserved by hpet_register.