Messages in this thread | | | Date | Wed, 21 Dec 2011 20:52:14 -0800 (PST) | From | david@lang ... | Subject | Re: RFC: android logger feedback request |
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On Thu, 22 Dec 2011, NeilBrown wrote:
> On Wed, 21 Dec 2011 16:36:21 -0800 Tim Bird <tim.bird@am.sony.com> wrote: > >> On 12/21/2011 03:19 PM, Greg KH wrote: >>> That all describes the current code, but you haven't described what's >>> wrong with the existing syslog interface that requires this new driver >>> to be written. And why can't the existing interface be fixed to address >>> these (potential) shortcomings? >> >> >>>> One specific question I have is where is the most appropriate >>>> place for this code to live, in the kernel source tree? >>>> Other embedded systems might want to use this system (it >>>> is simpler than syslog, and superior in some ways), so I don't >>>> think it should remain in an android-specific directory. >>> >>> What way is it superior? >> >> Here are some ways that this code is superior to syslog: > > It is certainly nice and simple. It really looks more like a filesystem than > a char device though... though they aren't really files so much as lossy > pipes. I don't think that's a problem though, lots of things in filesystems > don't behave exactly like files. > > If you created a 'logbuf' filesystem that used libfs to provide a single > directory in which privileged processes could create files then you wouldn't > need the kernel to "know" the allowed logs: radio, events, main, system. > The size could be set by ftruncate() (by privileged used again) rather than > being hardcoded. > > You would defined 'read' and 'write' much like you currently do to create a list of > datagrams in a circular buffer and replace the ioctls by more standard > interfaces: > > LOGGER_GET_LOG_BUG_SIZE would use 'stat' and the st_blocks field > LOGGER_GET_LOG_LEN would use 'stat' and the st_size field > LOGGER_GET_NEXT_ENTRY_LEN could use the FIONREAD ioctl > LOGGER_FLUSH_LOG could use ftruncate > > The result would be much the same amount of code, but an interface which has > fewer details hard-coded and is generally more versatile and accessible.
That sounds better than what has been done in android, but it is still _far_ more limited than doing something that could be replaced by a fairly standard syslog daemon.
David Lang
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