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

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Date:   Wed, 20 Jun 2018 00:06:19 +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>,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        Mark Brown <broonie@...nel.org>,
        Tomeu Vizoso <tomeu.vizoso@...labora.com>,
        Rob Herring <robh@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH] driver core: add a debugfs entry to show deferred devices

On Tue, Jun 19, 2018 at 11:59 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
>

FWIW,
Reviewed-by: Andy Shevchenko <andy.shevchenko@...il.com>

> Signed-off-by: Javier Martinez Canillas <javierm@...hat.com>
>
> ---
>
> Changes since RFC v1:
> - Remove unneeded ret variable from deferred_devs_show()
>
> Changes since RFC v2:
> - Use DEFINE_SHOW_ATTRIBUTE() macro.
> - Don't propagate debugfs_create_file() error.
> - Remove IS_ENABLED(CONFIG_DEBUG_FS) guards.
> - Drop RFC prefix.
>
>  drivers/base/dd.c | 22 ++++++++++++++++++++++
>  1 file changed, 22 insertions(+)
>
> diff --git a/drivers/base/dd.c b/drivers/base/dd.c
> index 1435d7281c6..8ec9e3cfbe4 100644
> --- a/drivers/base/dd.c
> +++ b/drivers/base/dd.c
> @@ -16,6 +16,7 @@
>   * Copyright (c) 2007-2009 Novell Inc.
>   */
>
> +#include <linux/debugfs.h>
>  #include <linux/device.h>
>  #include <linux/delay.h>
>  #include <linux/dma-mapping.h>
> @@ -224,6 +225,24 @@ void device_unblock_probing(void)
>         driver_deferred_probe_trigger();
>  }
>
> +/*
> + * 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;
> +}
> +DEFINE_SHOW_ATTRIBUTE(deferred_devs);
> +
>  /**
>   * deferred_probe_initcall() - Enable probing of deferred devices
>   *
> @@ -233,6 +252,9 @@ void device_unblock_probing(void)
>   */
>  static int deferred_probe_initcall(void)
>  {
> +       debugfs_create_file("deferred_devices", 0444, NULL, NULL,
> +                           &deferred_devs_fops);
> +
>         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