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util/char_dev: Add open_cdev()

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/dev/vfio/devices/vfioX may not exist. In that case it is still possible
to open /dev/char/$major:$minor instead. Add helper function to abstract
the cdev open.

Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Yi Liu <yi.l.liu@intel.com>
Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Tested-by: Eric Auger <eric.auger@redhat.com>
Tested-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Cédric Le Goater <clg@redhat.com>
This commit is contained in:
Yi Liu 2023-11-21 16:44:01 +08:00 • committed by Cédric Le Goater
parent 6e6d8ac62b
commit d6b5c4c1b5
4 changed files with 100 additions and 0 deletions
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81
util/chardev_open.c Normal file
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/*
* Copyright (c) 2019, Mellanox Technologies. All rights reserved.
* Copyright (C) 2023 Intel Corporation.
*
* This software is available to you under a choice of one of two
* licenses. You may choose to be licensed under the terms of the GNU
* General Public License (GPL) Version 2, available from the file
* COPYING in the main directory of this source tree, or the
* OpenIB.org BSD license below:
*
* Redistribution and use in source and binary forms, with or
* without modification, are permitted provided that the following
* conditions are met:
*
* - Redistributions of source code must retain the above
* copyright notice, this list of conditions and the following
* disclaimer.
*
* - Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following
* disclaimer in the documentation and/or other materials
* provided with the distribution.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
* BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
* ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*
* Authors: Yi Liu <yi.l.liu@intel.com>
*
* Copied from
* https://github.com/linux-rdma/rdma-core/blob/master/util/open_cdev.c
*
*/
#include "qemu/osdep.h"
#include "qemu/chardev_open.h"
static int open_cdev_internal(const char *path, dev_t cdev)
{
struct stat st;
int fd;
fd = qemu_open_old(path, O_RDWR);
if (fd == -1) {
return -1;
}
if (fstat(fd, &st) || !S_ISCHR(st.st_mode) ||
(cdev != 0 && st.st_rdev != cdev)) {
close(fd);
return -1;
}
return fd;
}
static int open_cdev_robust(dev_t cdev)
{
g_autofree char *devpath = NULL;
/*
* This assumes that udev is being used and is creating the /dev/char/
* symlinks.
*/
devpath = g_strdup_printf("/dev/char/%u:%u", major(cdev), minor(cdev));
return open_cdev_internal(devpath, cdev);
}
int open_cdev(const char *devpath, dev_t cdev)
{
int fd;
fd = open_cdev_internal(devpath, cdev);
if (fd == -1 && cdev != 0) {
return open_cdev_robust(cdev);
}
return fd;
}