On Wed, 21 Dec 2011 16:36:21 -0800 Tim Bird <tim.bird@xxxxxxxxxxx> 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. NeilBrown
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