On 12/21/2011 04:18 PM, john stultz wrote: > On Wed, 2011-12-21 at 15:19 -0800, Greg KH wrote: >> On Wed, Dec 21, 2011 at 02:59:15PM -0800, Tim Bird wrote: >>> Hi all, >>> >>> I'm looking for feedback on the Android logger code, to see what >>> it would take to make this code acceptable for inclusion in >>> the mainline kernel. >>> >>> Information about the features of Android logging system >>> can be found at: http://elinux.org/Android_Logging_System >>> >>> This system creates a new system-wide logging service, in >>> the kernel, for user-space message. It is more comparable >>> to syslog than to the kernel log buffer, as it holds only >>> user-space messages. It is optimized for write >>> performance, since most of the time the log is written to >>> and never read. It creates multiple log channels, to prevent >>> an abundance of log messages in one channel from overwriting >>> messages in another channel. The log channels have sizes >>> fixed at kernel compile-time. >>> >>> Log messages are stored in very simple in-kernel buffers, that >>> overflow old messages upon wrapping. A fixed set of attributes >>> (pid, tid, timestamp and message), is kept for each message. >>> By convention, Android puts a message priority and context tag >>> into each message. >>> >>> In Android, this system uses a fixed set of device nodes with >>> well-known names: /dev/log/main, /dev/log/events, /dev/log/radio >>> and /dev/log/system. >>> >>> Operations on the log are done via a character device, using >>> standard file operations and some ioctls. >>> >>> The code for this is below (I've moved it from linux-next >>> drivers/staging/android for my own testing). >>> >>> Please let me know what issues you see with this code. >> >> 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? Again, why not extend syslog? Why not "fix" >> syslog if this really is a superior thing? How does this tie into Kay >> and Lennard's proposal for work in this area? > > There is also some overlap functionality wise with pstore as well, as I > believe the logger is used as a known location in memory where messages > can be fetched from after a kernel panic or crash. I don't know if that's true or not. I think you may be thinking of Android's RAM console feature. If there's a way to save application messages over a reboot using the logger buffers, I'm unfamiliar with it. -- Tim ============================= Tim Bird Architecture Group Chair, CE Workgroup of the Linux Foundation Senior Staff Engineer, Sony Network Entertainment ============================= -- To unsubscribe from this list: send the line "unsubscribe linux-embedded" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
