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

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Message-ID: <CAHp75Vcn39N9rZ0UO3szGrODVLxek4X746uWs+RPXwy4i0s1Ug@mail.gmail.com>
Date:   Tue, 19 Jun 2018 22:53:07 +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 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.
>
>   $ cat /sys/kernel/debug/deferred_devices
>   48070000.i2c:twl@48:bci
>   musb-hdrc.0.auto
>   omapdrm.0

> +#if IS_ENABLED(CONFIG_DEBUG_FS)
> +#include <linux/debugfs.h>
> +
> +static struct dentry *deferred_devices;
> +
> +/*
> + * deferred_devs_show() - Show the devices in the deferred probe pending list.
> + */
> +static int deferred_devs_show(struct seq_file *s, void *data)
> +{
> +       struct device_private *curr;
> +
> +       mutex_lock(&deferred_probe_mutex);
> +
> +       list_for_each_entry(curr, &deferred_probe_pending_list, deferred_probe)
> +               seq_printf(s, "%s\n", dev_name(curr->device));
> +
> +       mutex_unlock(&deferred_probe_mutex);
> +
> +       return 0;
> +}
> +

> +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() ?

> +#endif /* IS_ENABLED(CONFIG_DEBUG_FS) */
> +
>  /**
>   * deferred_probe_initcall() - Enable probing of deferred devices
>   *
> @@ -233,6 +269,14 @@ void device_unblock_probing(void)
>   */
>  static int deferred_probe_initcall(void)
>  {
> +       if (IS_ENABLED(CONFIG_DEBUG_FS)) {
> +               deferred_devices = debugfs_create_file("deferred_devices",
> +                                                      0444, NULL, NULL,
> +                                                      &deferred_devs_fops);
> +               if (!deferred_devices)
> +                       return -ENOMEM;
> +       }
> +
>         driver_deferred_probe_enable = true;
>         driver_deferred_probe_trigger();
>         /* Sort as many dependencies as possible before exiting initcalls */
> --
> 2.17.1
>



-- 
With Best Regards,
Andy Shevchenko