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Diffstat (limited to 'Documentation/hpet.txt')
| -rw-r--r-- | Documentation/hpet.txt | 34 |
1 files changed, 18 insertions, 16 deletions
diff --git a/Documentation/hpet.txt b/Documentation/hpet.txt index 4e7cc8d3359b..e52457581f47 100644 --- a/Documentation/hpet.txt +++ b/Documentation/hpet.txt @@ -1,18 +1,21 @@ 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 two 32 timers. It is possible -to configure the first two timers as legacy replacements for 8254 and RTC periodic. A specification -done by INTEL and Microsoft can be found at http://www.intel.com/labs/platcomp/hpet/hpetspec.htm. - -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 +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 two 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/hardwaredesign/hpetspec.htm>. + +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. -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 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. #include <stdio.h> #include <stdlib.h> @@ -290,9 +293,8 @@ The kernel API has three interfaces exported from the driver: 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 +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. - - |