linux-kernel - Re: [PATCH] platform/x86: wmi: Fix printing info about WDG structure

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Date:   Sat, 27 May 2017 15:23:14 +0200
From:   Pali Rohár <pali.rohar@...il.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Darren Hart <dvhart@...radead.org>,
        Andy Shevchenko <andy@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        Platform Driver <platform-driver-x86@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] platform/x86: wmi: Fix printing info about WDG structure

On Saturday 27 May 2017 15:17:29 Pali Rohár wrote:
> On Saturday 27 May 2017 15:07:09 Andy Shevchenko wrote:
> > On Sat, May 27, 2017 at 2:51 PM, Pali Rohár <pali.rohar@...il.com>
> > 
> > wrote:
> > > object_id and notify_id are in one union structure and their
> > > meaning is defined by flags. Therefore do not print notify_id for
> > > non-event block and do not print object_id for event block.
> > > Remove also reserved member as it does not have any defined
> > > meaning or type yet.
> > > 
> > > As object_id and notify_id union members overlaps and have
> > > different types, it caused that kernel print to dmesg binary
> > > data. This patch eliminates it.
> > > 
> > > -       pr_info("\tobject_id: %c%c\n", g->object_id[0],
> > > g->object_id[1]); -       pr_info("\tnotify_id: %02X\n",
> > > g->notify_id);
> > > 
> > > -       pr_info("\treserved: %02X\n", g->reserved);
> > 
> > Do we need this? Commit message doesn't clarify.
> 
> I wrote to commit message that reserved does not have defined meaning
> nor type. Also reserved overlap with object_id[1] so for non-event
> should not be print at all. And as it is reserved, I removed it.
> 
> > > +       if (g->flags & ACPI_WMI_EVENT)
> > > +               pr_info("\tnotify_id: 0x%02X\n", g->notify_id);
> > > +       else
> > > 
> > > +               pr_info("\tobject_id: %c%c\n", g->object_id[0],
> > > g->object_id[1]);
> > 
> > If this can still contain non-printable characters the %*pE can
> > help instead.
> 
> Those are printable ASCII. object_id contains two characters which
> are suffix for ACPI method.
> 
> Problem was only for events when we tried to print notify_id as
> object_id. notify_id is binary and overlaps with object_id.

Before patch modprobe wmi debug_dump_wdg=1 print to dmesg:

wmi: 8D9DDCBC-A997-11DA-B012-B622A1EF5492:
wmi: 	object_id: AA
wmi: 	notify_id: 41
wmi: 	reserved: 41
wmi: 	instance_count: 1
wmi: 	flags: 0x0
wmi: A80593CE-A997-11DA-B012-B622A1EF5492:
wmi: 	object_id: BA
wmi: 	notify_id: 42
wmi: 	reserved: 41
wmi: 	instance_count: 1
wmi: 	flags: 0x2 ACPI_WMI_METHOD
wmi: 9DBB5994-A997-11DA-B012-B622A1EF5492:
wmi: 	object_id: <<some_binary_char>>
wmi: 	notify_id: D0
wmi: 	reserved: 00
wmi: 	instance_count: 1
wmi: 	flags: 0x8 ACPI_WMI_EVENT
wmi: A3776CE0-1E88-11DB-A98B-0800200C9A66:
wmi: 	object_id: BC
wmi: 	notify_id: 42
wmi: 	reserved: 43
wmi: 	instance_count: 1
wmi: 	flags: 0x0
wmi: 05901221-D566-11D1-B2F0-00A0C9062910:
wmi: 	object_id: MO
wmi: 	notify_id: 4D
wmi: 	reserved: 4F
wmi: 	instance_count: 1
wmi: 	flags: 0x0

(where <<some_binary_char>> was 0xD0)

After patch it prints:

wmi: 8D9DDCBC-A997-11DA-B012-B622A1EF5492:
wmi: 	object_id: AA
wmi: 	instance_count: 1
wmi: 	flags: 0x0
wmi: A80593CE-A997-11DA-B012-B622A1EF5492:
wmi: 	object_id: BA
wmi: 	instance_count: 1
wmi: 	flags: 0x2 ACPI_WMI_METHOD
wmi: 9DBB5994-A997-11DA-B012-B622A1EF5492:
wmi: 	notify_id: 0xD0
wmi: 	instance_count: 1
wmi: 	flags: 0x8 ACPI_WMI_EVENT
wmi: A3776CE0-1E88-11DB-A98B-0800200C9A66:
wmi: 	object_id: BC
wmi: 	instance_count: 1
wmi: 	flags: 0x0
wmi: 05901221-D566-11D1-B2F0-00A0C9062910:
wmi: 	object_id: MO
wmi: 	instance_count: 1
wmi: 	flags: 0x0

I hope it is more clear right now.

Basically output now contains only meaningful parsed members (event 
contains notify_id, method contains object_id).

-- 
Pali Rohár
pali.rohar@...il.com

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