netdev - Re: [PATCH v3 2/3] Bluetooth: Add sysfs entry to enable/disable devcoredump

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Date:   Fri, 8 Jul 2022 10:24:38 -0700
From:   Luiz Augusto von Dentz <luiz.dentz@...il.com>
To:     Manish Mandlik <mmandlik@...gle.com>
Cc:     Marcel Holtmann <marcel@...tmann.org>,
        "linux-bluetooth@...r.kernel.org" <linux-bluetooth@...r.kernel.org>,
        ChromeOS Bluetooth Upstreaming 
        <chromeos-bluetooth-upstreaming@...omium.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Johan Hedberg <johan.hedberg@...il.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "open list:NETWORKING [GENERAL]" <netdev@...r.kernel.org>
Subject: Re: [PATCH v3 2/3] Bluetooth: Add sysfs entry to enable/disable devcoredump

Hi Manish,

On Thu, Jul 7, 2022 at 3:15 PM Manish Mandlik <mmandlik@...gle.com> wrote:
>
> Since device/firmware dump is a debugging feature, we may not need it
> all the time. Add a sysfs attribute to enable/disable bluetooth
> devcoredump capturing. The default state of this feature would be
> disabled and it can be enabled by echoing 1 to enable_coredump sysfs
> entry as follow:
>
> $ echo 1 > /sys/class/bluetooth/<device>/enable_coredump
>
> Signed-off-by: Manish Mandlik <mmandlik@...gle.com>
> ---
>
> Changes in v3:
> - New patch in the series to enable/disable feature via sysfs entry
>
>  net/bluetooth/hci_sysfs.c | 36 ++++++++++++++++++++++++++++++++++++
>  1 file changed, 36 insertions(+)
>
> diff --git a/net/bluetooth/hci_sysfs.c b/net/bluetooth/hci_sysfs.c
> index 4e3e0451b08c..df0d54a5ae3f 100644
> --- a/net/bluetooth/hci_sysfs.c
> +++ b/net/bluetooth/hci_sysfs.c
> @@ -91,9 +91,45 @@ static void bt_host_release(struct device *dev)
>         module_put(THIS_MODULE);
>  }
>
> +#ifdef CONFIG_DEV_COREDUMP
> +static ssize_t enable_coredump_show(struct device *dev,
> +                                   struct device_attribute *attr,
> +                                   char *buf)
> +{
> +       struct hci_dev *hdev = to_hci_dev(dev);
> +
> +       return scnprintf(buf, 3, "%d\n", hdev->dump.enabled);
> +}
> +
> +static ssize_t enable_coredump_store(struct device *dev,
> +                                    struct device_attribute *attr,
> +                                    const char *buf, size_t count)
> +{
> +       struct hci_dev *hdev = to_hci_dev(dev);
> +
> +       /* Consider any non-zero value as true */
> +       if (simple_strtol(buf, NULL, 10))
> +               hdev->dump.enabled = true;
> +       else
> +               hdev->dump.enabled = false;
> +
> +       return count;
> +}
> +DEVICE_ATTR_RW(enable_coredump);
> +#endif
> +
> +static struct attribute *bt_host_attrs[] = {
> +#ifdef CONFIG_DEV_COREDUMP
> +       &dev_attr_enable_coredump.attr,
> +#endif
> +       NULL,
> +};
> +ATTRIBUTE_GROUPS(bt_host);
> +
>  static const struct device_type bt_host = {
>         .name    = "host",
>         .release = bt_host_release,
> +       .groups = bt_host_groups,
>  };
>
>  void hci_init_sysfs(struct hci_dev *hdev)
> --
> 2.37.0.rc0.161.g10f37bed90-goog

It seems devcoredump.c creates its own sysfs entries so perhaps this
should be included there and documented in sysfs-devices-coredump.

-- 
Luiz Augusto von Dentz