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SubjectRe: RFC: android logger feedback request
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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.

thanks
-john



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