linux-kernel - Re: [PATCH v4] USB hub_probe: rework ugly goto-into-compound-statement

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Date:   Thu, 10 Nov 2016 13:50:58 +0800
From:   Baolin Wang <baolin.wang@...aro.org>
To:     Eugene Korenevsky <ekorenevsky@...il.com>,
        LKML <linux-kernel@...r.kernel.org>,
        USB <linux-usb@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH v4] USB hub_probe: rework ugly goto-into-compound-statement

Hi,

On 9 November 2016 at 23:35, Eugene Korenevsky <ekorenevsky@...il.com> wrote:
> Rework smelling code (goto inside compound statement). Perhaps this is
> legacy. Anyway such code is not appropriate for Linux kernel.
>
> Changes since v3: fix typo
> Changes since v2: extract the code to static function
> Changes since v1: fix spaces instead of tab, add missing 'Signed-off-by'
>
> Signed-off-by: Eugene Korenevsky <ekorenevsky@...il.com>
> ---
>  drivers/usb/core/hub.c | 35 ++++++++++++++++++-----------------
>  1 file changed, 18 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
> index cbb1467..b770c8d 100644
> --- a/drivers/usb/core/hub.c
> +++ b/drivers/usb/core/hub.c
> @@ -1722,10 +1722,25 @@ static void hub_disconnect(struct usb_interface *intf)
>         kref_put(&hub->kref, hub_release);
>  }
>
> +static int hub_check_descriptor_sanity(struct usb_host_interface *desc)
> +{
> +       /* Some hubs have a subclass of 1, which AFAICT according to the */
> +       /*  specs is not defined, but it works */
> +       if (desc->desc.bInterfaceSubClass != 0 &&
> +           desc->desc.bInterfaceSubClass != 1)
> +               return 0;
> +
> +       /* Multiple endpoints? What kind of mutant ninja-hub is this? */
> +       if (desc->desc.bNumEndpoints != 1)
> +               return 0;

We usually return 0 as successful result, can you return kernel error
number if we check the descriptor failed? Or change the return value
of the function as bool type.

> +
> +       /* If it's not an interrupt in endpoint, we'd better punt! */
> +       return usb_endpoint_is_int_in(&desc->endpoint[0].desc);
> +}
> +
>  static int hub_probe(struct usb_interface *intf, const struct usb_device_id *id)
>  {
>         struct usb_host_interface *desc;
> -       struct usb_endpoint_descriptor *endpoint;
>         struct usb_device *hdev;
>         struct usb_hub *hub;
>
> @@ -1800,25 +1815,11 @@ static int hub_probe(struct usb_interface *intf, const struct usb_device_id *id)
>         }
>  #endif
>
> -       /* Some hubs have a subclass of 1, which AFAICT according to the */
> -       /*  specs is not defined, but it works */
> -       if ((desc->desc.bInterfaceSubClass != 0) &&
> -           (desc->desc.bInterfaceSubClass != 1)) {
> -descriptor_error:
> +       if (!hub_check_descriptor_sanity(desc)) {
>                 dev_err(&intf->dev, "bad descriptor, ignoring hub\n");
>                 return -EIO;
>         }
>
> -       /* Multiple endpoints? What kind of mutant ninja-hub is this? */
> -       if (desc->desc.bNumEndpoints != 1)
> -               goto descriptor_error;
> -
> -       endpoint = &desc->endpoint[0].desc;
> -
> -       /* If it's not an interrupt in endpoint, we'd better punt! */
> -       if (!usb_endpoint_is_int_in(endpoint))
> -               goto descriptor_error;
> -
>         /* We found a hub */
>         dev_info(&intf->dev, "USB hub found\n");
>
> @@ -1845,7 +1846,7 @@ static int hub_probe(struct usb_interface *intf, const struct usb_device_id *id)
>         if (id->driver_info & HUB_QUIRK_CHECK_PORT_AUTOSUSPEND)
>                 hub->quirk_check_port_auto_suspend = 1;
>
> -       if (hub_configure(hub, endpoint) >= 0)
> +       if (hub_configure(hub, &desc->endpoint[0].desc) >= 0)
>                 return 0;
>
>         hub_disconnect(intf);
> --
> 2.10.2
>
>
> --
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-- 
Baolin.wang
Best Regards