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From:   Andy Shevchenko <andy.shevchenko@gmail.com>
Date:   Mon, 4 Mar 2019 08:50:39 +0200
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Subject: Re: [PATCH v3 10/12] hikey960: Support usb functionality of Hikey960
To:     Chunfeng Yun <chunfeng.yun@mediatek.com>
Cc:     Yu Chen <chenyu56@huawei.com>, USB <linux-usb@vger.kernel.org>,
        devicetree <devicetree@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        John Stultz <john.stultz@linaro.org>,
        Suzhuangluan <suzhuangluan@hisilicon.com>,
        Kongfei <kongfei@hisilicon.com>, liuyu712@hisilicon.com,
        wanghu17@hisilicon.com, butao@hisilicon.com,
        Yao Chen <chenyao11@huawei.com>, fangshengzhou@hisilicon.com,
        lipengcheng8@huawei.com, songxiaowei <songxiaowei@hisilicon.com>,
        xu yiping <xuyiping@hisilicon.com>, xuyoujun4@huawei.com,
        yudongbin@hisilicon.com, zangleigang@hisilicon.com,
        Arnd Bergmann <arnd@arndb.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Binghui Wang <wangbinghui@hisilicon.com>,
        Heikki Krogerus <heikki.krogerus@linux.intel.com>
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On Mon, Mar 4, 2019 at 3:47 AM Chunfeng Yun <chunfeng.yun@mediatek.com> wrote:
> On Sat, 2019-03-02 at 17:05 +0800, Yu Chen wrote:

> > +     hisi_hikey_usb->role_sw = usb_role_switch_get(dev);
> > +     if (!hisi_hikey_usb->role_sw)
> > +             return -EPROBE_DEFER;
> Here return EPROBE_DEFFER means the related device_connection is
> registered after this probe is called, right?
> if not, use IS_ERR_OR_NULL then return PTR_ERR is enough

How enough? If return value is NULL it would be transformered to 0,
which is success return code from the ->probe() which means we will
have ->probed() and not functional device.

Am I missing something?

-- 
With Best Regards,
Andy Shevchenko