linux-kernel - Re: [PATCH v7 4/9] acpi/arm64: Add GTDT table parse driver

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Message-ID: <CADyBb7tLyABzWFEW_8A3bK9XeWiHJjh7TqWQc=vDn5O_WUJX5w@mail.gmail.com>
Date:	Sat, 16 Jul 2016 10:24:35 +0800
From:	Fu Wei <fu.wei@...aro.org>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	"Rafael J. Wysocki" <rafael@...nel.org>,
	Len Brown <lenb@...nel.org>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Marc Zyngier <marc.zyngier@....com>,
	Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
	Sudeep Holla <sudeep.holla@....com>,
	Hanjun Guo <hanjun.guo@...aro.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linaro-acpi@...ts.linaro.org" <linaro-acpi@...ts.linaro.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	rruigrok@...eaurora.org, harba@...eaurora.org,
	Christopher Covington <cov@...eaurora.org>,
	Timur Tabi <timur@...eaurora.org>,
	G Gregory <graeme.gregory@...aro.org>,
	Al Stone <al.stone@...aro.org>, Jon Masters <jcm@...hat.com>,
	wei@...hat.com, Arnd Bergmann <arnd@...db.de>,
	Wim Van Sebroeck <wim@...ana.be>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	Suravee Suthikulanit <Suravee.Suthikulpanit@....com>,
	Leo Duran <leo.duran@....com>,
	Guenter Roeck <linux@...ck-us.net>,
	"linux-watchdog@...r.kernel.org" <linux-watchdog@...r.kernel.org>,
	David Miller <davem@...emloft.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	kvalo@...eaurora.org, Jiri Slaby <jslaby@...e.cz>,
	Christoffer Dall <christoffer.dall@...aro.org>,
	Julien Grall <julien.grall@....com>
Subject: Re: [PATCH v7 4/9] acpi/arm64: Add GTDT table parse driver

Hi Rafeal,

On 16 July 2016 at 05:22, Rafael J. Wysocki <rjw@...ysocki.net> wrote:
> On Saturday, July 16, 2016 12:32:14 AM Fu Wei wrote:
>> Hi Rafael,
>>
>> On 15 July 2016 at 21:07, Rafael J. Wysocki <rjw@...ysocki.net> wrote:
>> > On Friday, July 15, 2016 02:15:27 PM Rafael J. Wysocki wrote:
>> >> On Friday, July 15, 2016 03:32:35 PM Fu Wei wrote:
>> >> > Hi Rafael,
>> >> >
>> >
>> > [cut]
>> >
>> >> > >
>> >> > >> +               return 0;
>> >> > >> +       }
>> >> > >> +
>> >> > >> +       if (!gtdt->platform_timer_count) {
>> >> > >> +               pr_info("No Platform Timer.\n");
>> >> > >> +               return 0;
>> >> > >> +       }
>> >> > >> +
>> >> > >> +       acpi_gtdt_desc.platform_timer_start = (void *)gtdt +
>> >> > >> +                                             gtdt->platform_timer_offset;
>> >> > >> +       if (acpi_gtdt_desc.platform_timer_start <
>> >> > >> +           (void *)table + sizeof(struct acpi_table_gtdt)) {
>> >> > >> +               pr_err(FW_BUG "Platform Timer pointer error.\n");
>> >> > >
>> >> > > Why pr_err()?
>> >> >
>> >> > if (true), that means the GTDT table has bugs.
>> >> >
>> >>
>> >> And that's not a very useful piece of information unless you're debugging the
>> >> platform, is it?
>> >
>> > FWIW, I'm not a big fan of printing "your firmware is buggy" type of messages
>> > (especially at the "error" log level or higher) unless they can be clearly
>> > connected to a specific type of functional failure.
>> >
>> > So if you want to pring an error-level message, something like "I cannot do X
>> > because of the firmware bug Y" would be better IMO.
>>
>> So can I do this:
>> pr_err(FW_BUG "Can NOT init platform_timer pointer, because of the
>> GTDT table bug\n");
>>
>> or pr_debug(FW_BUG "Can NOT init platform_timer_start, because of
>> platform_timer_offset bug in GTDT\n");
>>
>> or just delete it?
>>
>> which one do you prefer?  I think maybe should provide some clue for
>> users to fix the problem  :-)
>
> And how exactly would they fix it then?
>
>>
>> any thought ?
>
> If you print variable or function names and the like, the message should be
> a debug one, because that's information that can only be understood by
> developers (some developers are users too, but they are a minority).
>
> If you want to report an error, say what is not working (or not available
> etc) and why (if you know the reason at the time the message is printed).

Great thanks, I guess I got you point.

maybe just a very simple message like:
pr_err(FW_BUG "Failed to init table: GTDT table is buggy.\n");

I will also check other pr_* , if I can update them


>
> Thanks,
> Rafael
>



-- 
Best regards,

Fu Wei
Software Engineer
Red Hat