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    SubjectRe: RFC: android logger feedback request
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    On Wed, 2011-12-21 at 16:42 -0800, Tim Bird wrote:
    > 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.

    I may very well be confusing things. I had thought apanic pulled the
    logger data, but maybe I'm wrong.

    thanks
    -john




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