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

[Bin Meng]

Hi Simon,

On Thu, Sep 21, 2017 at 12:58 PM, Simon Glass <sjg at chromium.org> wrote:
> 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?
>

The blk driver can save the logs to a predefined block address for
permanent storage. Or file system driver can send the logs to a file.

Regards,
Bin