/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@xxxxxxxxxx> Signed-off-by: Yi Liu <yi.l.liu@xxxxxxxxx> --- MAINTAINERS | 6 +++++ include/qemu/char_dev.h | 16 ++++++++++++ util/chardev_open.c | 58 +++++++++++++++++++++++++++++++++++++++++ util/meson.build | 1 + 4 files changed, 81 insertions(+) create mode 100644 include/qemu/char_dev.h create mode 100644 util/chardev_open.c diff --git a/MAINTAINERS b/MAINTAINERS index c6aa4e7fd0..0b3ade4170 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -3171,6 +3171,12 @@ S: Maintained F: include/qemu/iova-tree.h F: util/iova-tree.c +cdev Open +M: Yi Liu <yi.l.liu@xxxxxxxxx> +S: Maintained +F: include/qemu/char_dev.h +F: util/chardev_open.c + elf2dmp M: Viktor Prutyanov <viktor.prutyanov@xxxxxxxxxxxx> S: Maintained diff --git a/include/qemu/char_dev.h b/include/qemu/char_dev.h new file mode 100644 index 0000000000..79877fb24d --- /dev/null +++ b/include/qemu/char_dev.h @@ -0,0 +1,16 @@ +/* + * QEMU Chardev Helper + * + * Copyright (C) 2022 Intel Corporation. + * + * Authors: Yi Liu <yi.l.liu@xxxxxxxxx> + * + * This work is licensed under the terms of the GNU GPL, version 2. See + * the COPYING file in the top-level directory. + */ + +#ifndef QEMU_CHARDEV_HELPERS_H +#define QEMU_CHARDEV_HELPERS_H + +int open_cdev(const char *devpath, dev_t cdev); +#endif diff --git a/util/chardev_open.c b/util/chardev_open.c new file mode 100644 index 0000000000..133fad06ec --- /dev/null +++ b/util/chardev_open.c @@ -0,0 +1,58 @@ +/* + * Copyright (C) 2022 Intel Corporation. + * Copyright (c) 2019, Mellanox Technologies. All rights reserved. + * + * Authors: Yi Liu <yi.l.liu@xxxxxxxxx> + * + * This work is licensed under the terms of the GNU GPL, version 2. See + * the COPYING file in the top-level directory. + * + * Copied from https://github.com/linux-rdma/rdma-core/blob/master/util/open_cdev.c + * + */ +#ifndef _GNU_SOURCE +#define _GNU_SOURCE +#endif +#include "qemu/osdep.h" +#include "qemu/char_dev.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) +{ + char *devpath; + int ret; + + /* + * 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)); + ret = open_cdev_internal(devpath, cdev); + g_free(devpath); + return ret; +} + +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; +} diff --git a/util/meson.build b/util/meson.build index 8f16018cd4..eff15d3826 100644 --- a/util/meson.build +++ b/util/meson.build @@ -95,4 +95,5 @@ if have_block util_ss.add(files('filemonitor-stub.c')) endif util_ss.add(when: 'CONFIG_LINUX', if_true: files('vfio-helpers.c')) + util_ss.add(when: 'CONFIG_LINUX', if_true: files('chardev_open.c')) endif -- 2.27.0
