[U-Boot] [PATCH 06/13] log: Add an implemention of logging

[Simon Glass]

Hi Bin,

On 20 September 2017 at 08:41, Bin Meng <bmeng.cn at gmail.com> wrote:
>
> Hi Simon,
>
> On Wed, Sep 20, 2017 at 9:50 PM, Simon Glass <sjg at chromium.org> wrote:
> > Hi Bin,
> >
> > On 17 September 2017 at 21:45, Bin Meng <bmeng.cn at gmail.com> wrote:
> >> Hi Simon,
> >>
> >> On Sun, Sep 17, 2017 at 5:23 AM, Simon Glass <sjg at chromium.org> wrote:
> >>> Add the logging header file and implementation with some configuration
> >>> options to control it.
> >>>
> >>> Signed-off-by: Simon Glass <sjg at chromium.org>
> >>> ---
> >>>
> >>>  MAINTAINERS                       |   9 ++
> >>>  common/Kconfig                    |  56 +++++++++
> >>>  common/Makefile                   |   1 +
> >>>  common/log.c                      | 246 +++++++++++++++++++++++++++++++++++++
> >>>  include/asm-generic/global_data.h |   5 +
> >>>  include/log.h                     | 247 ++++++++++++++++++++++++++++++++++++--
> >>>  6 files changed, 555 insertions(+), 9 deletions(-)
> >>>  create mode 100644 common/log.c
> >>>
> >>> diff --git a/MAINTAINERS b/MAINTAINERS
> >>> index 04acf2b89d..eb420afa8d 100644
> >>> --- a/MAINTAINERS
> >>> +++ b/MAINTAINERS
> >>> @@ -290,6 +290,15 @@ S: Maintained
> >>>  T:     git git://git.denx.de/u-boot-i2c.git
> >>>  F:     drivers/i2c/
> >>>
> >>> +LOGGING
> >>> +M:     Simon Glass <sjg at chromium.org>
> >>> +S:     Maintained
> >>> +T:     git git://git.denx.de/u-boot.git
> >>> +F:     common/log.c
> >>> +F:     cmd/log.c
> >>> +F:     test/log/log_test.c
> >>> +F:     test/py/tests/test_log.py
> >>
> >> test/log/log_test.c and test/py/tests/test_log.py have not been
> >> introduced at this point.
> >
> > OK I can tweak that,
> > [..]
> >
> >>> +/**
> >>> + * struct log_driver - a driver which accepts and processes log records
> >>> + *
> >>> + * @name: Name of driver
> >>> + */
> >>> +struct log_driver {
> >>> +       const char *name;
> >>> +       /**
> >>> +        * emit() - emit a log record
> >>> +        *
> >>> +        * Called by the log system to pass a log record to a particular driver
> >>> +        * for processing. The filter is checked before calling this function.
> >>> +        */
> >>> +       int (*emit)(struct log_device *ldev, struct log_rec *rec);
> >>> +};
> >>> +
> >>
> >> So we are creating a new type of non-DM driver which is log-specific?
> >> How about we add this emit to the existing uclass driver that can be
> >> used as the log driver? (eg: blk devices with file system?)
> >
> > Yes that's right. I think I can link it to DM once it starts up, but a
> > logging of DM start-up is useful.
> >
> > Re your idea are you saying add an emit() method to UCLASS_BLK?
> >
>
> Yep, something like
>
> #ifdef CONFIG_LOG
>     .log_emit = xxx_log_emit,
> #endif
>
> Probably we need a flag to find out which driver provides such log
> functionality.

So what would the block driver do in that function? I guess I don't
understand what it is for. Can you please give me more information?

Regards,
Simon