{"version":"https:\/\/jsonfeed.org\/version\/1","title":"My Feed Title","home_page_url":"https:\/\/tm23forest.com\/contents","feed_url":"https:\/\/tm23forest.com\/contents.json","description":"TM23FOREST.COM ","author":{"name":"Tosh Morry"},"items":[{"title":"Linux\u306eSystemCall\u756a\u53f7\u4e00\u89a7","date_published":"2026-01-25T20:54:00+09:00","id":"https:\/\/tm23forest.com\/contents\/linux-systemcall-numbers","url":"https:\/\/tm23forest.com\/contents\/linux-systemcall-numbers","content_html":"

LinuxのSystem Call番号一覧をunistd.h<\/a>から抽出した。名称はwww.man7.org<\/code>へのリンクとなっている。<\/p>\n\n

System Call番号一覧<\/h2>\n
\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
Number<\/th>\nSystem call<\/th>\n<\/tr>\n<\/thead>\n
0<\/td>\nio_setup<\/a><\/td>\n<\/tr>\n
1<\/td>\nio_destroy<\/a><\/td>\n<\/tr>\n
2<\/td>\nio_submit<\/a><\/td>\n<\/tr>\n
3<\/td>\nio_cancel<\/a><\/td>\n<\/tr>\n
4<\/td>\nio_getevents<\/a><\/td>\n<\/tr>\n
5<\/td>\nsetxattr<\/a><\/td>\n<\/tr>\n
6<\/td>\nlsetxattr<\/a><\/td>\n<\/tr>\n
7<\/td>\nfsetxattr<\/a><\/td>\n<\/tr>\n
8<\/td>\ngetxattr<\/a><\/td>\n<\/tr>\n
9<\/td>\nlgetxattr<\/a><\/td>\n<\/tr>\n
10<\/td>\nfgetxattr<\/a><\/td>\n<\/tr>\n
11<\/td>\nlistxattr<\/a><\/td>\n<\/tr>\n
12<\/td>\nllistxattr<\/a><\/td>\n<\/tr>\n
13<\/td>\nflistxattr<\/a><\/td>\n<\/tr>\n
14<\/td>\nremovexattr<\/a><\/td>\n<\/tr>\n
15<\/td>\nlremovexattr<\/a><\/td>\n<\/tr>\n
16<\/td>\nfremovexattr<\/a><\/td>\n<\/tr>\n
17<\/td>\ngetcwd<\/a><\/td>\n<\/tr>\n
18<\/td>\nlookup_dcookie<\/a><\/td>\n<\/tr>\n
19<\/td>\neventfd2<\/a><\/td>\n<\/tr>\n
20<\/td>\nepoll_create1<\/a><\/td>\n<\/tr>\n
21<\/td>\nepoll_ctl<\/a><\/td>\n<\/tr>\n
22<\/td>\nepoll_pwait<\/a><\/td>\n<\/tr>\n
23<\/td>\ndup<\/a><\/td>\n<\/tr>\n
24<\/td>\ndup3<\/a><\/td>\n<\/tr>\n
26<\/td>\ninotify_init1<\/a><\/td>\n<\/tr>\n
27<\/td>\ninotify_add_watch<\/a><\/td>\n<\/tr>\n
28<\/td>\ninotify_rm_watch<\/a><\/td>\n<\/tr>\n
29<\/td>\nioctl<\/a><\/td>\n<\/tr>\n
30<\/td>\nioprio_set<\/a><\/td>\n<\/tr>\n
31<\/td>\nioprio_get<\/a><\/td>\n<\/tr>\n
32<\/td>\nflock<\/a><\/td>\n<\/tr>\n
33<\/td>\nmknodat<\/a><\/td>\n<\/tr>\n
34<\/td>\nmkdirat<\/a><\/td>\n<\/tr>\n
35<\/td>\nunlinkat<\/a><\/td>\n<\/tr>\n
36<\/td>\nsymlinkat<\/a><\/td>\n<\/tr>\n
37<\/td>\nlinkat<\/a><\/td>\n<\/tr>\n
38<\/td>\nrenameat<\/a><\/td>\n<\/tr>\n
39<\/td>\numount2<\/a><\/td>\n<\/tr>\n
40<\/td>\nmount<\/a><\/td>\n<\/tr>\n
41<\/td>\npivot_root<\/a><\/td>\n<\/tr>\n
42<\/td>\nnfsservctl<\/a><\/td>\n<\/tr>\n
47<\/td>\nfallocate<\/a><\/td>\n<\/tr>\n
48<\/td>\nfaccessat<\/a><\/td>\n<\/tr>\n
49<\/td>\nchdir<\/a><\/td>\n<\/tr>\n
50<\/td>\nfchdir<\/a><\/td>\n<\/tr>\n
51<\/td>\nchroot<\/a><\/td>\n<\/tr>\n
52<\/td>\nfchmod<\/a><\/td>\n<\/tr>\n
53<\/td>\nfchmodat<\/a><\/td>\n<\/tr>\n
54<\/td>\nfchownat<\/a><\/td>\n<\/tr>\n
55<\/td>\nfchown<\/a><\/td>\n<\/tr>\n
56<\/td>\nopenat<\/a><\/td>\n<\/tr>\n
57<\/td>\nclose<\/a><\/td>\n<\/tr>\n
58<\/td>\nvhangup<\/a><\/td>\n<\/tr>\n
59<\/td>\npipe2<\/a><\/td>\n<\/tr>\n
60<\/td>\nquotactl<\/a><\/td>\n<\/tr>\n
61<\/td>\ngetdents64<\/a><\/td>\n<\/tr>\n
63<\/td>\nread<\/a><\/td>\n<\/tr>\n
64<\/td>\nwrite<\/a><\/td>\n<\/tr>\n
65<\/td>\nreadv<\/a><\/td>\n<\/tr>\n
66<\/td>\nwritev<\/a><\/td>\n<\/tr>\n
67<\/td>\npread64<\/a><\/td>\n<\/tr>\n
68<\/td>\npwrite64<\/a><\/td>\n<\/tr>\n
69<\/td>\npreadv<\/a><\/td>\n<\/tr>\n
70<\/td>\npwritev<\/a><\/td>\n<\/tr>\n
72<\/td>\npselect6<\/a><\/td>\n<\/tr>\n
73<\/td>\nppoll<\/a><\/td>\n<\/tr>\n
74<\/td>\nsignalfd4<\/a><\/td>\n<\/tr>\n
75<\/td>\nvmsplice<\/a><\/td>\n<\/tr>\n
76<\/td>\nsplice<\/a><\/td>\n<\/tr>\n
77<\/td>\ntee<\/a><\/td>\n<\/tr>\n
78<\/td>\nreadlinkat<\/a><\/td>\n<\/tr>\n
81<\/td>\nsync<\/a><\/td>\n<\/tr>\n
82<\/td>\nfsync<\/a><\/td>\n<\/tr>\n
83<\/td>\nfdatasync<\/a><\/td>\n<\/tr>\n
84<\/td>\nsync_file_range2<\/a><\/td>\n<\/tr>\n
84<\/td>\nsync_file_range<\/a><\/td>\n<\/tr>\n
85<\/td>\ntimerfd_create<\/a><\/td>\n<\/tr>\n
86<\/td>\ntimerfd_settime<\/a><\/td>\n<\/tr>\n
87<\/td>\ntimerfd_gettime<\/a><\/td>\n<\/tr>\n
88<\/td>\nutimensat<\/a><\/td>\n<\/tr>\n
89<\/td>\nacct<\/a><\/td>\n<\/tr>\n
90<\/td>\ncapget<\/a><\/td>\n<\/tr>\n
91<\/td>\ncapset<\/a><\/td>\n<\/tr>\n
92<\/td>\npersonality<\/a><\/td>\n<\/tr>\n
93<\/td>\nexit<\/a><\/td>\n<\/tr>\n
94<\/td>\nexit_group<\/a><\/td>\n<\/tr>\n
95<\/td>\nwaitid<\/a><\/td>\n<\/tr>\n
96<\/td>\nset_tid_address<\/a><\/td>\n<\/tr>\n
97<\/td>\nunshare<\/a><\/td>\n<\/tr>\n
98<\/td>\nfutex<\/a><\/td>\n<\/tr>\n
99<\/td>\nset_robust_list<\/a><\/td>\n<\/tr>\n
100<\/td>\nget_robust_list<\/a><\/td>\n<\/tr>\n
101<\/td>\nnanosleep<\/a><\/td>\n<\/tr>\n
102...<\/td><\/tr><\/tbody><\/table><\/div>","tags":["Linux"]},{"title":"ALSA subdevice from tinyalsa utilities","date_published":"2026-01-04T22:05:00+09:00","id":"https:\/\/tm23forest.com\/contents\/alsa-subdevice-from-tinyalsa-utilities","url":"https:\/\/tm23forest.com\/contents\/alsa-subdevice-from-tinyalsa-utilities","content_html":"

As noted on my previous post<\/a>, tinyalsa code is not capable to playback\/capture stream from designated subdevice. Fortunately, tinyalsa source code is easy to extend so that implementing subdevice option is straight forward.<\/p>\n\n

Basics<\/h2>\n

In tinyalsa API, pcm_open<\/code> is used instead of snd_pcm_open<\/code>. To designate subdevice, consumer process need to call certain ioctl to \/dev\/snd\/controlC%u<\/code> before calling pcm_open<\/code>. This is minimal code snipped to demonstrate it.<\/p>\n

#include <unistd.h>   \/* close *\/\n#include <fcntl.h>      \/* open *\/\n#include <sys\/ioctl.h>  \/* ioctl *\/\n#include <sound\/asound.h>  \/* SNDRV_CTL_IOCTL_PCM_PREFER_SUBDEVICE *\/\n\nstruct pcm *pcm_open_with_subdevice(unsigned int card, unsigned int device,\n                            unsigned int subdevice, unsigned int flags, struct pcm_config *config)\n{\n    char fn[256];\n    int fd;\n\n    snprintf(fn, sizeof(fn), \"\/dev\/snd\/controlC%u\", card);\n    fd = open(fn, 0);\n    if (fd < 0) {\n        fprintf(stderr, \"failed to open %s\\n\", fn);\n        return NULL;\n    }\n\n    if (ioctl(fd, SNDRV_CTL_IOCTL_PCM_PREFER_SUBDEVICE, &subdevice) < 0) {\n        fprintf(stderr, \"failed to set subdevice %u\\n\", subdevice);\n        close(fd);\n        return NULL;\n    }\n\n    pcm = pcm_open(card, device, flags, config);\n\n    return pcm;\n}<\/code><\/pre>\n
Note that, if unexisting subdevice is passed to this implementation, this program goes into infinite loop. By default, ALSA kernel side will wait until subdevice become available: pcm_native.c:2848<\/a>. To avoid this behavior, adding PCM_NONBLOCK<\/code> to pcm_open flags argument enable...<\/p>","tags":["ALSA"]},{"title":"Virtio Sound multi-stream configuration\/testing on QEMU","date_published":"2026-01-03T23:12:00+09:00","id":"https:\/\/tm23forest.com\/contents\/virtio-sound-multi-stream-configuration-testing-on-qemu","url":"https:\/\/tm23forest.com\/contents\/virtio-sound-multi-stream-configuration-testing-on-qemu","content_html":"
Virtio Sound is a paravirtualized sound device to access sound device from virtual machine. Unlike other virtual sound device among QEMU implementations, Virtio Sound doesn't assume any physical sound device to derive the virtual device behavior. Instead, Virtio Sound relays on VIRTIO specification to define device behavior so that virtual machine can exchange sound data without any restriction coming from physical device in general. One such example is the number of streams per single sound device. This article demonstrate how the number of streams is configured on QEMU and how it is tested from virtual machie side.<\/p>\n\n
Prerequisite<\/h2>\n