linux-kernel - Re: [PATCH v2 01/11] coresight-etm4x: Adding CoreSight ETM4x driver

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Message-ID: <CANLsYkywp0o8YtjkFwfvEiAje-w2jCWbs_82SiD29xdirA_7vQ@mail.gmail.com>
Date:	Fri, 1 May 2015 08:39:05 -0600
From:	Mathieu Poirier <mathieu.poirier@...aro.org>
To:	Paul Bolle <pebolle@...cali.nl>
Cc:	Greg KH <gregkh@...uxfoundation.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>, linux-api@...r.kernel.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Kaixu Xia <kaixu.xia@...aro.org>,
	Chunyan Zhang <zhang.chunyan@...aro.org>
Subject: Re: [PATCH v2 01/11] coresight-etm4x: Adding CoreSight ETM4x driver

On 30 April 2015 at 15:29, Paul Bolle <pebolle@...cali.nl> wrote:
> On Wed, 2015-04-29 at 11:16 -0600, Mathieu Poirier wrote:
>> --- a/drivers/hwtracing/coresight/Kconfig
>> +++ b/drivers/hwtracing/coresight/Kconfig
>
>> +config CORESIGHT_SOURCE_ETM4X
>> +     bool "CoreSight Embedded Trace Macrocell 4.x driver"
>> +     depends on ARM64
>> +     select CORESIGHT_LINKS_AND_SINKS
>> +     help
>> +       This driver provides support for the ETM4.x tracer module, tracing the
>> +       instructions that a processor is executing. This is primarily useful
>> +       for instruction level tracing. Depending on the implemented version
>> +       data tracing may also be available.
>
> (Please add an empty line here.)
>
>>  endif
>
>> --- a/drivers/hwtracing/coresight/Makefile
>> +++ b/drivers/hwtracing/coresight/Makefile
>
>> +obj-$(CONFIG_CORESIGHT_SOURCE_ETM4X) += coresight-etm4x.o
>
> CORESIGHT_SOURCE_ETM4X is a bool symbol, so coresight-etm4x.o can never
> be part of a module, right?
>
> (If I'm wrong, we're done here.)
>
>> --- /dev/null
>> +++ b/drivers/hwtracing/coresight/coresight-etm4x.c
>
>> +#include <linux/module.h>
>
> Is this include needed?

It is needed for "module_param_named()".

>
>> +static struct amba_driver etm4x_driver = {
>> +     .drv = {
>> +             .name   = "coresight-etm4x",
>> +             .owner  = THIS_MODULE,
>
> For built-in code this is basically equivalent to NULL (see
> include/linux/export.h).
>
>> +     },
>> +     .probe          = etm4_probe,
>> +     .remove         = etm4_remove,
>> +     .id_table       = etm4_ids,
>> +};
>> +
>> +module_amba_driver(etm4x_driver);
>
> In a message I sent a short while ago, I suggested that for built-in
> only code this is equivalent to calling
>     amba_driver_register(&etm4x_driver);
>
> from within a function marked with some sort of *initcall(). Please
> double check.

Built-in as a module or not using "module_amba_driver()" deals with
redundant code.

>
>> +MODULE_LICENSE("GPL v2");
>> +MODULE_DESCRIPTION("CoreSight Embedded Trace Macrocell v4 driver");
>
> These macros will be effectively be preprocessed away for built-in only
> code.

I agree.

>
> (There is also a reference to module_param_named(). I don't know by
> heart how that works for built-in only code, sorry.)
>
>
> Paul Bolle
>
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