mirror of
https://github.com/edk2-porting/linux-next.git
synced 2024-12-24 21:24:00 +08:00
770fe30a46
Loop devices today have a fixed pre-allocated number of usually 8.
The number can only be changed at module init time. To find a free
device to use, /dev/loop%i needs to be scanned, and all devices need
to be opened until a free one is possibly found.
This adds a new /dev/loop-control device node, that allows to
dynamically find or allocate a free device, and to add and remove loop
devices from the running system:
LOOP_CTL_ADD adds a specific device. Arg is the number
of the device. It returns the device i or a negative
error code.
LOOP_CTL_REMOVE removes a specific device, Arg is the
number the device. It returns the device i or a negative
error code.
LOOP_CTL_GET_FREE finds the next unbound device or allocates
a new one. No arg is given. It returns the device i or a
negative error code.
The loop kernel module gets automatically loaded when
/dev/loop-control is accessed the first time. The alias
specified in the module, instructs udev to create this
'dead' device node, even when the module is not loaded.
Example:
cfd = open("/dev/loop-control", O_RDWR);
# add a new specific loop device
err = ioctl(cfd, LOOP_CTL_ADD, devnr);
# remove a specific loop device
err = ioctl(cfd, LOOP_CTL_REMOVE, devnr);
# find or allocate a free loop device to use
devnr = ioctl(cfd, LOOP_CTL_GET_FREE);
sprintf(loopname, "/dev/loop%i", devnr);
ffd = open("backing-file", O_RDWR);
lfd = open(loopname, O_RDWR);
err = ioctl(lfd, LOOP_SET_FD, ffd);
Cc: Tejun Heo <tj@kernel.org>
Cc: Karel Zak <kzak@redhat.com>
Signed-off-by: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
66 lines
1.8 KiB
C
66 lines
1.8 KiB
C
#ifndef _LINUX_MISCDEVICE_H
|
|
#define _LINUX_MISCDEVICE_H
|
|
#include <linux/module.h>
|
|
#include <linux/major.h>
|
|
|
|
/*
|
|
* These allocations are managed by device@lanana.org. If you use an
|
|
* entry that is not in assigned your entry may well be moved and
|
|
* reassigned, or set dynamic if a fixed value is not justified.
|
|
*/
|
|
|
|
#define PSMOUSE_MINOR 1
|
|
#define MS_BUSMOUSE_MINOR 2
|
|
#define ATIXL_BUSMOUSE_MINOR 3
|
|
/*#define AMIGAMOUSE_MINOR 4 FIXME OBSOLETE */
|
|
#define ATARIMOUSE_MINOR 5
|
|
#define SUN_MOUSE_MINOR 6
|
|
#define APOLLO_MOUSE_MINOR 7
|
|
#define PC110PAD_MINOR 9
|
|
/*#define ADB_MOUSE_MINOR 10 FIXME OBSOLETE */
|
|
#define WATCHDOG_MINOR 130 /* Watchdog timer */
|
|
#define TEMP_MINOR 131 /* Temperature Sensor */
|
|
#define RTC_MINOR 135
|
|
#define EFI_RTC_MINOR 136 /* EFI Time services */
|
|
#define SUN_OPENPROM_MINOR 139
|
|
#define DMAPI_MINOR 140 /* DMAPI */
|
|
#define NVRAM_MINOR 144
|
|
#define SGI_MMTIMER 153
|
|
#define STORE_QUEUE_MINOR 155
|
|
#define I2O_MINOR 166
|
|
#define MICROCODE_MINOR 184
|
|
#define TUN_MINOR 200
|
|
#define MWAVE_MINOR 219 /* ACP/Mwave Modem */
|
|
#define MPT_MINOR 220
|
|
#define MPT2SAS_MINOR 221
|
|
#define UINPUT_MINOR 223
|
|
#define HPET_MINOR 228
|
|
#define FUSE_MINOR 229
|
|
#define KVM_MINOR 232
|
|
#define BTRFS_MINOR 234
|
|
#define AUTOFS_MINOR 235
|
|
#define MAPPER_CTRL_MINOR 236
|
|
#define LOOP_CTRL_MINOR 237
|
|
#define MISC_DYNAMIC_MINOR 255
|
|
|
|
struct device;
|
|
|
|
struct miscdevice {
|
|
int minor;
|
|
const char *name;
|
|
const struct file_operations *fops;
|
|
struct list_head list;
|
|
struct device *parent;
|
|
struct device *this_device;
|
|
const char *nodename;
|
|
mode_t mode;
|
|
};
|
|
|
|
extern int misc_register(struct miscdevice * misc);
|
|
extern int misc_deregister(struct miscdevice *misc);
|
|
|
|
#define MODULE_ALIAS_MISCDEV(minor) \
|
|
MODULE_ALIAS("char-major-" __stringify(MISC_MAJOR) \
|
|
"-" __stringify(minor))
|
|
#endif
|