RE: [PATCH v3 25/37] util/char_dev: Add open_cdev()

[Duan, Zhenzhong]

>-----Original Message-----
>From: Cédric Le Goater <clg@redhat.com>
>Sent: Monday, October 30, 2023 10:54 PM
>Subject: Re: [PATCH v3 25/37] util/char_dev: Add open_cdev()
>
>On 10/26/23 12:30, Zhenzhong Duan wrote:
>> From: Yi Liu <yi.l.liu@intel.com>
>>
>> /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>
>> Signed-off-by: Cédric Le Goater <clg@redhat.com>
>> ---
>>   MAINTAINERS                 |  6 +++
>>   include/qemu/chardev_open.h | 16 ++++++++
>>   util/chardev_open.c         | 81 +++++++++++++++++++++++++++++++++++++
>>   util/meson.build            |  1 +
>>   4 files changed, 104 insertions(+)
>>   create mode 100644 include/qemu/chardev_open.h
>>   create mode 100644 util/chardev_open.c
>>
>> diff --git a/MAINTAINERS b/MAINTAINERS
>> index 7aa57ab16f..123e999bee 100644
>> --- a/MAINTAINERS
>> +++ b/MAINTAINERS
>> @@ -3447,6 +3447,12 @@ S: Maintained
>>   F: include/qemu/iova-tree.h
>>   F: util/iova-tree.c
>>
>> +cdev Open
>> +M: Yi Liu <yi.l.liu@intel.com>
>> +S: Maintained
>> +F: include/qemu/chardev_open.h
>> +F: util/chardev_open.c
>> +
>>   elf2dmp
>>   M: Viktor Prutyanov <viktor.prutyanov@phystech.edu>
>>   S: Maintained
>> diff --git a/include/qemu/chardev_open.h b/include/qemu/chardev_open.h
>> new file mode 100644
>> index 0000000000..6580d351c6
>> --- /dev/null
>> +++ b/include/qemu/chardev_open.h
>> @@ -0,0 +1,16 @@
>> +/*
>> + * QEMU Chardev Helper
>> + *
>> + * Copyright (C) 2023 Intel Corporation.
>> + *
>> + * Authors: Yi Liu <yi.l.liu@intel.com>
>> + *
>> + * 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..005d2b81bd
>> --- /dev/null
>> +++ b/util/chardev_open.c
>> @@ -0,0 +1,81 @@
>> +/*
>> + * 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;
>
>Please initialize g_autofree variables ( = NULL)

Thanks for point out, will fix.

BRs.
Zhenzhong