linux-kernel - Re: [PATCH v1 1/4] mhi_bus: core: Add support for MHI host interface

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Date:   Sat, 28 Apr 2018 07:28:17 -0700
From:   Sujeev Dias <sdias@...eaurora.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Arnd Bergmann <arnd@...db.de>, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, Tony Truong <truong@...eaurora.org>
Subject: Re: [PATCH v1 1/4] mhi_bus: core: Add support for MHI host interface

Thanks for quick feedback


On 04/27/2018 12:22 AM, Greg Kroah-Hartman wrote:
> On Thu, Apr 26, 2018 at 07:23:28PM -0700, Sujeev Dias wrote:
>> MHI Host Interface is a communication protocol to be used by the host
>> to control and communcate with modem over a high speed peripheral bus.
>> This module will allow host to communicate with external devices that
>> support MHI protocol.
>>
>> Signed-off-by: Sujeev Dias <sdias@...eaurora.org>
> No one else has ever reviewed this code before?  That's not good, please
> at the very least, have someone else at your company go over it first.
> I don't want to be the ones having to point out all of the "obvious"
> issues :)
>
This code has gone thru rigorous code review and testing, before I 
submit next patch
I will have multiple people sign off on it.
>> ---
>>   Documentation/00-INDEX                        |    2 +
>>   Documentation/devicetree/bindings/bus/mhi.txt |  141 +++
>>   Documentation/mhi.txt                         |  235 ++++
>>   drivers/bus/Kconfig                           |   17 +
>>   drivers/bus/Makefile                          |    1 +
>>   drivers/bus/mhi/Makefile                      |    8 +
>>   drivers/bus/mhi/core/Makefile                 |    1 +
>>   drivers/bus/mhi/core/mhi_boot.c               |  593 ++++++++++
>>   drivers/bus/mhi/core/mhi_dtr.c                |  177 +++
>>   drivers/bus/mhi/core/mhi_init.c               | 1290 +++++++++++++++++++++
>>   drivers/bus/mhi/core/mhi_internal.h           |  732 ++++++++++++
>>   drivers/bus/mhi/core/mhi_main.c               | 1476 +++++++++++++++++++++++++
>>   drivers/bus/mhi/core/mhi_pm.c                 | 1177 ++++++++++++++++++++
>>   include/linux/mhi.h                           |  694 ++++++++++++
>>   include/linux/mod_devicetable.h               |   11 +
>>   15 files changed, 6555 insertions(+)
> And a 6555 line patch is a bit hard to consume all at once.  Can't this
> be split up into much more reviewable chunks?  Look at how some of the
> other new bus subsystems got added to the tree recently.  They were
> submitted in longer patch series, but smaller sized patches
> individually.  That makes things much easier to review.
>
> For example, there is no reason your debugfs stuff needs to be in this
> initial patch.  That should be in a separate one, right?  Same for
> firmware download.  Please take the time to break this up into logical
> steps.
>
> Like my son's math teacher keeps telling him, "show your work, not just
> an answer at the bottom of the page".
>
> Also, it is required by the DT maintainers to split that file alone up
> into a separate patch to be even considered for merging.
>
> One thing I can tell you right now that isn't acceptable:
That is interesting because internally it's separated, and I squash them 
thinking
it was preferred. I will separate them out to functional blocks
>> +#ifdef CONFIG_MHI_DEBUG
> Don't have a separate config option for debugging.  No one will enable
> it, which makes it pointless.   Everything has to be dynamic these days.
Intention was to completely compile out MHI_VERB messages because we 
have those messages in
data path.  For release build, we wanted to reduce as much mips as 
possible. However, for
debugging these messages are extremely helpful.

I will look into tracepoints...
>> +
>> +#define MHI_VERB(fmt, ...) do { \
>> +		if (mhi_cntrl->klog_lvl <= MHI_MSG_LVL_VERBOSE) \
>> +			pr_debug("[D][%s] " fmt, __func__, ##__VA_ARGS__);\
>> +} while (0)
>> +
>> +#else
>> +
>> +#define MHI_VERB(fmt, ...)
>> +
>> +#endif
>> +
>> +#define MHI_LOG(fmt, ...) do {	\
>> +		if (mhi_cntrl->klog_lvl <= MHI_MSG_LVL_INFO) \
>> +			pr_info("[I][%s] " fmt, __func__, ##__VA_ARGS__);\
>> +} while (0)
>> +
>> +#define MHI_ERR(fmt, ...) do {	\
>> +		if (mhi_cntrl->klog_lvl <= MHI_MSG_LVL_ERROR) \
>> +			pr_err("[E][%s] " fmt, __func__, ##__VA_ARGS__); \
>> +} while (0)
>> +
>> +#define MHI_CRITICAL(fmt, ...) do { \
>> +		if (mhi_cntrl->klog_lvl <= MHI_MSG_LVL_CRITICAL) \
>> +			pr_alert("[C][%s] " fmt, __func__, ##__VA_ARGS__); \
>> +} while (0)
>> +
> And do not roll your own debugging/logging macros.  Use what is given to
> you (dev_info(), dev_err(), dev_dbg()), they are there for a reason.  By
> going around them, you circumvent the whole of the kernel logging
> infrastructure and declare that your tiny bus is somehow more "special"
> than it.
>
> And I doubt you want to make such a statement :)

well :).. I will remove them in next revision.
> thanks,
>
> greg k-h
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Thanks
Sujeev
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