linux-kernel - Re: [RFC PATCH v2] driver core: add a debugfs entry to show deferred devices

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Date:   Tue, 19 Jun 2018 22:55:20 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Javier Martinez Canillas <javierm@...hat.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Mark Brown <broonie@...nel.org>,
        Tomeu Vizoso <tomeu.vizoso@...labora.com>,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        Rob Herring <robh@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [RFC PATCH v2] driver core: add a debugfs entry to show deferred devices

On Tue, Jun 19, 2018 at 10:53 PM, Andy Shevchenko
<andy.shevchenko@...il.com> wrote:
> On Tue, Jun 19, 2018 at 9:33 PM, Javier Martinez Canillas
> <javierm@...hat.com> wrote:
>> For debugging purposes it may be useful to know what are the devices whose
>> probe function was deferred. Add a debugfs entry showing that information.

>> +static int deferred_devs_open(struct inode *inode, struct file *file)
>> +{
>> +       return single_open(file, deferred_devs_show, inode->i_private);
>> +}
>> +
>> +static const struct file_operations deferred_devs_fops = {
>> +       .owner = THIS_MODULE,
>> +       .open = deferred_devs_open,
>> +       .read = seq_read,
>> +       .llseek = seq_lseek,
>> +       .release = single_release,
>> +};
>
> Isn't this DEFINE_SHOW_ATTRIBUTE() ?

Besides that, you are summoning Greg's dark side :-)
See below.

>> +       if (IS_ENABLED(CONFIG_DEBUG_FS)) {
>> +               deferred_devices = debugfs_create_file("deferred_devices",
>> +                                                      0444, NULL, NULL,
>> +                                                      &deferred_devs_fops);

>> +               if (!deferred_devices)
>> +                       return -ENOMEM;

This must not prevent the execution. So, the check introduces actually
a regression.

>> +       }

-- 
With Best Regards,
Andy Shevchenko