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([2001:a61:137b:5001:be5a:c750:b487:ff1b]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-427c77a8084sm2035035e9.19.2024.07.17.08.27.52 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 17 Jul 2024 08:27:53 -0700 (PDT) Message-ID: Date: Wed, 17 Jul 2024 17:27:51 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH next] usb: usbfs: Add reset_resume for usbfs To: Alan Stern , Hongyu Xie Cc: oneukum@suse.com, gregkh@linuxfoundation.org, brauner@kernel.org, jlayton@kernel.org, jack@suse.cz, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, xiehongyu1@kylinos.cn References: <20240711084321.44916-1-xiehongyu1@kylinos.cn> <527927b8-9475-47da-bf2b-7a5d9e81e470@suse.com> <9ef72886-13b8-46cf-a0aa-54dad36102e9@rowland.harvard.edu> <2a80d11d-029f-4e7e-9a8e-3abae1034add@suse.com> <429eb27a-578a-4208-8ce1-89434b8d739f@rowland.harvard.edu> <3073c8ce-1923-4816-a442-41b4cc333af9@suse.com> <6419a4e9-e084-4eb6-8376-9202930ea8be@kylinos.cn> <45b87923-d256-4c5e-8167-8ef764add1e9@kylinos.cn> <5413aa3b-92ba-4367-b720-2fa4161638b5@rowland.harvard.edu> Content-Language: en-US From: Oliver Neukum In-Reply-To: <5413aa3b-92ba-4367-b720-2fa4161638b5@rowland.harvard.edu> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 17.07.24 15:44, Alan Stern wrote: > On Wed, Jul 17, 2024 at 11:13:39AM +0800, Hongyu Xie wrote: >> From: Hongyu Xie >> >> >> >> On 2024/7/17 10:05, Alan Stern wrote: > > That's right, it should be possible to avoid rebinding. But we can't do > this until we have some way to tell the userspace driver that a reset > has occurred. Oliver's idea is to do this by returning a special error > code for the next ioctl, and I can't think of anything better. I wish you could, for this is supremely inelegant. In particular it forces user space to reinit the device when it is needed, instead of when it is idle. Yet, I think conceptually the first ioctl absolutely must fail, because the device state has been lost. Regards Oliver