>-----Original Message----- >From: Daniel P. Berrangé <[email protected]> >Sent: Wednesday, September 20, 2023 8:39 PM >Subject: Re: [PATCH v1 17/22] util/char_dev: Add open_cdev() > >On Wed, Aug 30, 2023 at 06:37:49PM +0800, Zhenzhong Duan wrote: >> From: Yi Liu <[email protected]> >> >> /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 <[email protected]> >> Signed-off-by: Yi Liu <[email protected]> >> Signed-off-by: Zhenzhong Duan <[email protected]> >> --- >> MAINTAINERS | 6 ++++ >> include/qemu/char_dev.h | 16 +++++++++++ >> util/chardev_open.c | 61 +++++++++++++++++++++++++++++++++++++++++ > >Using the same naming scheme for the .c and .h is strongly desired.
Got it. > >> util/meson.build | 1 + >> 4 files changed, 84 insertions(+) >> create mode 100644 include/qemu/char_dev.h >> create mode 100644 util/chardev_open.c >> >> diff --git a/MAINTAINERS b/MAINTAINERS >> index 04663fbb6f..74d18593fe 100644 >> --- a/MAINTAINERS >> +++ b/MAINTAINERS >> @@ -3372,6 +3372,12 @@ S: Maintained >> F: include/qemu/iova-tree.h >> F: util/iova-tree.c >> >> +cdev Open >> +M: Yi Liu <[email protected]> >> +S: Maintained >> +F: include/qemu/char_dev.h >> +F: util/chardev_open.c >> + > > >> diff --git a/util/chardev_open.c b/util/chardev_open.c >> new file mode 100644 >> index 0000000000..d03e415131 >> --- /dev/null >> +++ b/util/chardev_open.c >> @@ -0,0 +1,61 @@ >> +/* >> + * Copyright (C) 2023 Intel Corporation. >> + * Copyright (c) 2019, Mellanox Technologies. All rights reserved. >> + * >> + * Authors: Yi Liu <[email protected]> >> + * >> + * 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 >> + * >> + */ > >Since this is GPL-2.0-only, IMHO it would be preferrable to keep it >out of the util/ directory, as we're aiming to not add further 2.0 >only code, except for specific subdirs. This only appears to be used >by code under hw/vfio/, whcih is one of the dirs still permitting >2.0-only code. So I think better to keep this file where it is used. I'll copy the original license header to preserve the GPL OR BSD choice. As it's not restricted by GPL-2.0-only now, I plan to keep it in util/. Let me know if you still prefer to move to hw/vifo/. > >> +#ifndef _GNU_SOURCE >> +#define _GNU_SOURCE >> +#endif > >This is set globally for building all files in QEMU Will remove it. > >> +#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; > >g_autofree for this... Will do. > >> + 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); > >...avoids the need for g_free, and also avoids the need for >the intermediate 'ret' variable. Yes. Thanks Zhenzhong
