linux-kernel - Re: [PATCH] gpiolib: demote the hogging log messages to debug

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Date:   Sun, 11 Jun 2023 07:48:23 -0500
From:   Frank Rowand <frowand.list@...il.com>
To:     Rob Herring <robh+dt@...nel.org>,
        Bartosz Golaszewski <brgl@...ev.pl>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Kent Gibson <warthog618@...il.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org,
        Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH] gpiolib: demote the hogging log messages to debug

On 6/11/23 07:39, Frank Rowand wrote:
> On 6/9/23 08:47, Rob Herring wrote:
>> On Mon, Jun 5, 2023 at 6:53 AM Bartosz Golaszewski <brgl@...ev.pl> wrote:
>>>
>>> From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
>>>
>>> Drivers should be silent when they work correctly. There's no reason to
>>> emit info messages when GPIO lines are hogged. Demote the message to
>>> debug.
>>>
>>> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
>>> Suggested-by: Kent Gibson <warthog618@...il.com>
>>> ---
>>>  drivers/gpio/gpiolib.c |  2 +-
>>>  drivers/of/unittest.c  | 16 ++++++++--------
>>>  2 files changed, 9 insertions(+), 9 deletions(-)
>>>
>>> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
>>> index a7220e04a93e..e4515bda8915 100644
>>> --- a/drivers/gpio/gpiolib.c
>>> +++ b/drivers/gpio/gpiolib.c
>>> @@ -4243,7 +4243,7 @@ int gpiod_hog(struct gpio_desc *desc, const char *name,
>>>         /* Mark GPIO as hogged so it can be identified and removed later */
>>>         set_bit(FLAG_IS_HOGGED, &desc->flags);
>>>
>>> -       gpiod_info(desc, "hogged as %s%s\n",
>>> +       gpiod_dbg(desc, "hogged as %s%s\n",
>>>                 (dflags & GPIOD_FLAGS_BIT_DIR_OUT) ? "output" : "input",
>>>                 (dflags & GPIOD_FLAGS_BIT_DIR_OUT) ?
>>>                   (dflags & GPIOD_FLAGS_BIT_DIR_VAL) ? "/high" : "/low" : "");
>>> diff --git a/drivers/of/unittest.c b/drivers/of/unittest.c
>>> index 2191c0136531..0060334a98a7 100644
>>> --- a/drivers/of/unittest.c
>>> +++ b/drivers/of/unittest.c
>>> @@ -1849,19 +1849,19 @@ static void __init of_unittest_overlay_gpio(void)
>>>          * driver is registered
>>>          */
>>>
>>> -       EXPECT_BEGIN(KERN_INFO,
>>> +       EXPECT_BEGIN(KERN_DEBUG,
>>>                      "gpio-<<int>> (line-B-input): hogged as input\n");
>>
>> As debug messages are normally off, I think you can just remove these.
> 
> This patch is an example of exactly why the message level is the first parameter
> passed to EXPECT_*().  The test results are then _always_ valid, not just
> _normally_.

One should never say never.  One should never say always. :-)

Yes, there is still the exception where debug can be enabled independently
for drivers/gpio/gpiolib.c  vs for drivers/of/unittest.c.  And dynamic
debug can make things even more wonky.

-Frank

> 
> -Frank
> 
>>
>> Rob
>