hpet_example - HPET sample Application のバックアップ(No.7)

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hpet_example - HPET sample Application へ行く。

hpet_example †

HPET (High Precision Event Timer) ドライバ /drivers/char/hpet.c の動作を理解するために、実際に動かすアプリケーション・プログラム hpet_example.tar.gz を使います。このプログラムは /Documentation/timers/hpet_example.c を修正して作成してあります。/Documentation/timers/hpet.txt で hpet_example.c について概要が書かれています。情報量は多く有りません。ioctl() API の仕様詳細は書かれていません。

↑

ioctl API †

↑

HPET driver's APIs †

↑

Interrupt On - HPET_IE_ON †

SYNOPSIS
```
int ioctl(int fd, HPET_IE_ON);
```
PRECONDITION
- Set interrupt frequency by HPET_IRQFREQ.
- Enable or disable periodic interrupt by HPET_EPI or HPET_DPI.
DESCRIPTION
Enable timer interrupt assigned to file descriptor fd. When the timer interrupts processor, file descriptor fd becomes ready with event (POLLIN | POLLRDNORM) and also raise signal if set file status O_ASYNC and valid signal or process group number to fd.
RETURN VALUE
- 0 Success
- -1 Error
ERRORS
- EBADF Invalid file descriptor fd.
- EIO It occurs one of following conditions.
  - Invalid interrupt frequency.
  - Interrupt frequency has not been set.
  - Can't request IRQ handler. It may chipset or BIOS bug.
- EBUSY
  - Already enabled interrupt.

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Interrupt Off - HPET_IE_OFF †

SYNOPSIS
```
int ioctl(int fd, HPET_IE_OFF);
```
DESCRIPTION
Disable timer interrupt assigned to file descriptor fd.
RETURN VALUE
- 0 Success
- -1 Error
ERRORS
- EBADF Invalid file descriptor fd.

↑

Get Information - HPET_INFO †

SYNOPSIS

struct hpet_info {
	unsigned long  hi_ireqfreq; /* Period or time in Hz */
	unsigned long  hi_flags;    /* Information: 0x0: Not supported periodic int., 0x10: Supported periodic int. */
	unsigned short hi_hpet;     /* HPET device number, [0..TheNumberOfHPETDevicesInPlatform-1] */
	unsigned short hi_timer;    /* Timer number in HPET device, [0..31] */
};
int ioctl(int fd, HPET_INFO, /* out */ struct hpet_info *info);

DESCRIPTION
Get timer information assigned to file descriptor fd. ioctl call with HPET_INFO stores timer information to *info. This ioctl call fills hpet_info members as follows.

member	description
hi_ireqfreq	Interrupt frequency in Hz.
hi_flags	Timer capability. The value will be as follows, 0x00UL This timer doesn't have hardware implemented periodic interrupt. 0x10UL This timer has hardware implemented periodic interrupt.
hi_hpet	HPET device number on platform. It satisfies (hi_hpet >= 0) && (hi_hpet < M), where M is the number of HPET devices (circuit blocks) on platform.
hi_timer	Timer number in HPET device. It satisfies (hi_timer >= 0) && (hi_timer < N), where N is the number of timers in HPET device and N <= 32. NOTE: You may see {hi_hpet, hi_timer} == {0, 2} at first opened HPET timer, because the timer 0 and timer 1 replaces PIT(programmable Interval Timer) and RTC(Real Time Clock).

RETURN VALUE
- 0 Success
- -1 Error
ERRORS
- EBADF Invalid file descriptor fd.
- EFAULT info points an inaccessible memory area.

↑

Enable hardware periodic interrupt - HPET_EPI †

SYNOPSIS
```
int ioctl(int fd, HPET_EPI);
```
DESCRIPTION
Enable hardware implemented periodic interrupt at timer assigned to file descriptor fd, and disable software assisted periodic interrupt. Call HPET_EPI ioctl() before enable interrupt HPET_IE_ON.
RETURN VALUE
- 0 Success
- -1 Error
ERRORS
- EBADF Invalid file descriptor fd.
- ENXIO The timer's hardware assigned to file descriptor fd doesn't support periodic interrupt.

↑

Disable hardware periodic interrupt - HPET_DPI †

SYNOPSIS
```
int ioctl(int fd, HPET_DPI);
```
DESCRIPTION
Disable hardware implemented periodic interrupt at timer assigned to file descriptor fd, and enable software assisted periodic interrupt. Call HPET_DPI ioctl() before enable interrupt HPET_IE_ON.
When using HPET timer with HPET_DPI (disabling hardware periodic interrupt), HPET driver updates interrupt time in interrupt handler. So timer interrupts periodically and interrupt period includes software response time delay.
RETURN VALUE
- 0 Success
- -1 Error
ERRORS
- EBADF Invalid file descriptor fd.
- ENXIO The timer's hardware assigned to file descriptor fd doesn't support periodic interrupt.

↑

Set Interrupt Frequency in Hz - HPET_IRQFREQ †

SYNOPSIS

int ioctl(int fd, HPET_IRQFREQ, unsigned long frequency);

DESCRIPTION
RETURN
- 0 Success
- -1 Error
ERRORS
- EACCESS Process doesn't have capability CAP_SYS_RESOURCE and try to set frequency more than the value read from /proc/sys/dev/hpet/max-user-freq. The default value read from max-user-freq is 64.
- EINVAL Frequency is zero.

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File System API's †

To see more details refer to man 2 fcntl.

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F_GETOWN, F_GETOWN_EX †

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F_SETOWN, F_SETOWN_EX †

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F_GETFL †

SYNOPSIS
```
int fcntl(int fd, F_GETFL);
```
DESCRIPTION
Use this function to set or clear O_ASYNC flag to file descriptor fd. See the description of F_SETFL.

↑

F_SETFL †

SYNOPSIS
```
int fcntl(int fd, F_SETFL, int flags);
```

DESCRIPTION
To raise signal on timer event, let flags be ORed with O_ASYNC, see following pseudo code piece.

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!
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!
!

{       int     flags;
        flags = fcntl(fd, F_GETFL);
        if (flags < 0) {
                /* error handling. */
        }
        flags |= O_ASYNC;
        if (fcntl(fd, F_SETFL, flags) != 0) {
                /* error handling. */
        }
}

↑

F_GETSIG †

SYNOPSIS
```
int fcntl(int fd, F_GETSIG);
```
DESCRIPTION
Get the signal number will be raised on timer interrupt.

↑

F_SETSIG †

SYNOPSIS

int fcntl(int fd, F_SETSIG, int signal);

DESCRIPTION
Set the signal number will be raised on timer interrupt.