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authorSam Bishop <sam@bishop.dhs.org>2006-08-28 18:52:15 -0400
committerGreg Kroah-Hartman <gregkh@suse.de>2006-09-27 14:58:48 -0400
commit06afff00bcab0e384afbef70194fd3469532abdf (patch)
tree7c1da770bfa971697ab1c1615ba4731d85890549 /Documentation
parent341323269258ab8484077a9c70db804fbae6ae93 (diff)
USB doc patch 2
A little more detail on how and when to poll() /proc/bus/usb/devices. Signed-off-by: Sam Bishop <sam@bishop.dhs.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/DocBook/usb.tmpl25
1 files changed, 18 insertions, 7 deletions
diff --git a/Documentation/DocBook/usb.tmpl b/Documentation/DocBook/usb.tmpl
index 8a28f76b9359..3608472d7b74 100644
--- a/Documentation/DocBook/usb.tmpl
+++ b/Documentation/DocBook/usb.tmpl
@@ -453,14 +453,25 @@
453 file in your Linux kernel sources. 453 file in your Linux kernel sources.
454 </para> 454 </para>
455 455
456 <para>Otherwise the main use for this file from programs 456 <para>This file, in combination with the poll() system call, can
457 is to poll() it to get notifications of usb devices 457 also be used to detect when devices are added or removed:
458 as they're plugged or unplugged. 458<programlisting>int fd;
459 To see what changed, you'd need to read the file and 459struct pollfd pfd;
460 compare "before" and "after" contents, scan the filesystem, 460
461 or see its hotplug event. 461fd = open("/proc/bus/usb/devices", O_RDONLY);
462pfd = { fd, POLLIN, 0 };
463for (;;) {
464 /* The first time through, this call will return immediately. */
465 poll(&amp;pfd, 1, -1);
466
467 /* To see what's changed, compare the file's previous and current
468 contents or scan the filesystem. (Scanning is more precise.) */
469}</programlisting>
470 Note that this behavior is intended to be used for informational
471 and debug purposes. It would be more appropriate to use programs
472 such as udev or HAL to initialize a device or start a user-mode
473 helper program, for instance.
462 </para> 474 </para>
463
464 </sect1> 475 </sect1>
465 476
466 <sect1> 477 <sect1>