ata_pio_queue_task(9) [suse man page]

ATA_PIO_QUEUE_TASK(9)						  libata Library					     ATA_PIO_QUEUE_TASK(9)

NAME

       ata_pio_queue_task - Queue port_task

SYNOPSIS

       void ata_pio_queue_task(struct ata_port * ap, void * data, unsigned long delay);

ARGUMENTS

       ap
	   The ata_port to queue port_task for

       data
	   data for fn to use

       delay
	   delay time in msecs for workqueue function

DESCRIPTION

       Schedule fn(data) for execution after delay jiffies using port_task. There is one port_task per port and it's the user(low level driver)'s
       responsibility to make sure that only one task is active at any given time.

       libata core layer takes care of synchronization between port_task and EH.  ata_pio_queue_task may be ignored for EH synchronization.

LOCKING

       Inherited from caller.

AUTHOR

       Jeff Garzik
	   Author.

COPYRIGHT

Kernel Hackers Manual 2.6.					     July 2010						     ATA_PIO_QUEUE_TASK(9)

delay(9F)						   Kernel Functions for Drivers 						 delay(9F)

NAME

       delay - delay execution for a specified number of clock ticks

SYNOPSIS

       #include <sys/ddi.h>

       void delay(clock_t ticks);

INTERFACE LEVEL

       Architecture independent level 1 (DDI/DKI).

PARAMETERS

       ticks	 The number of clock cycles to delay.

DESCRIPTION

       delay() provides a mechanism for a driver to delay its execution for a given period of time. Since the speed of the clock varies among sys-
       tems, drivers should base their time values on microseconds and use drv_usectohz(9F) to convert microseconds into clock ticks.

       delay() uses timeout(9F) to schedule an internal function to be called after the specified amount of time has elapsed. delay()  then  waits
       until  the  function  is  called. Because timeout() is subject to priority inversion, drivers waiting on behalf of processes with real-time
       constraints should use cv_timedwait(9F) rather than delay().

       delay() does not busy-wait. If busy-waiting is required, use drv_usecwait(9F).

CONTEXT

       delay() can be called from user and kernel contexts.

EXAMPLES

       Example 1 delay() Example

       Before a driver I/O routine allocates buffers and stores any user data in them, it checks the status of the device (line 12). If the device
       needs  manual intervention (such as, needing to be refilled with paper), a message is displayed on the system console (line 14). The driver
       waits an allotted time (line 17) before repeating the procedure.

	  1  struct  device  {	  /* layout of physical device registers */
	  2	     int      control; /* physical device control word */
	  3	     int      status;  /* physical device status word */
	  4	     short    xmit_char;    /* transmit character to device */
	  5  };
	  6
	  7
		. . .
	  9   /* get device registers  */
	 10	 register struct device *rp = ...
	 11
	 12	 while (rp->status & NOPAPER) {  /* while printer is out of paper */
	 13	  /* display message and ring bell */
		  /* on system console */
	 14	     cmn_err(CE_WARN, "^07",
	 15			       (getminor(dev) & 0xf));
	 16	     /* wait one minute and try again */
	 17	     delay(60 * drv_usectohz(1000000));
	 18	 }

SEE ALSO

       biodone(9F), biowait(9F), cv_timedwait(9F), ddi_in_panic(9F), drv_hztousec(9F), drv_usectohz(9F),  drv_usecwait(9F),  timeout(9F),  untime-
       out(9F)

       Writing Device Drivers

SunOS 5.11							    15 Oct 2001 							 delay(9F)