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Add a dead_cdevsw which does its best to return ENXIO if at all possible.

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In devsw() return dead_cdevsw instead of NULL in case the dev_t does not
have a si_devsw.

This may improve our survival chances with devices which go away unexpectedly.
This commit is contained in:
Poul-Henning Kamp 2003-02-20 15:35:54 +00:00
parent 568ef33fa2
commit 02574b19e1
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=111179
1 changed files with 53 additions and 3 deletions
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56
sys/kern/kern_conf.c
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@ -29,6 +29,7 @@
#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/systm.h>
#include <sys/bio.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/sysctl.h>
@ -66,15 +67,64 @@ static int ready_for_devs;
static int free_devt;
SYSCTL_INT(_debug, OID_AUTO, free_devt, CTLFLAG_RW, &free_devt, 0, "");
/* Define a dead_cdevsw for use when devices leave unexpectedly. */
static int
enxio(void)
{
return (ENXIO);
}
#define dead_open (d_open_t *)enxio
#define dead_close (d_close_t *)enxio
#define dead_read (d_read_t *)enxio
#define dead_write (d_write_t *)enxio
#define dead_ioctl (d_ioctl_t *)enxio
#define dead_poll nopoll
#define dead_mmap nommap
static void
dead_strategy(struct bio *bp)
{
biofinish(bp, NULL, ENXIO);
}
#define dead_dump (d_dump_t *)enxio
static int
dead_psize(dev_t dev)
{
return (-1);
}
#define dead_kqfilter (d_kqfilter_t *)enxio
static struct cdevsw dead_cdevsw = {
/* open */ dead_open,
/* close */ dead_close,
/* read */ dead_read,
/* write */ dead_write,
/* ioctl */ dead_ioctl,
/* poll */ dead_poll,
/* mmap */ dead_mmap,
/* strategy */ dead_strategy,
/* name */ "dead",
/* maj */ 255,
/* dump */ dead_dump,
/* psize */ dead_psize,
/* flags */ 0,
/* kqfilter */ dead_kqfilter
};
struct cdevsw *
devsw(dev_t dev)
{
if (dev->si_devsw)
return (dev->si_devsw);
if (dev->si_devsw)
return (dev->si_devsw);
return (NULL);
return (&dead_cdevsw);
}
/*