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([2001:a61:135e:f101:ca2c:3cad:536e:8acf]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4976bd45fc5sm40613485e9.1.2026.07.29.07.43.45 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 29 Jul 2026 07:43:45 -0700 (PDT) Message-ID: <5d36c6a8-bbc9-4d5f-8670-2993bdeb857f@suse.com> Date: Wed, 29 Jul 2026 16:43:44 +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 v4 4/4] media: uvcvideo: defer streaming restart after hibernation snapshot To: Alan Stern , Haowen Tu Cc: hansg@kernel.org, gregkh@linuxfoundation.org, kernel@uniontech.com, laurent.pinchart@ideasonboard.com, lenb@kernel.org, linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, linux-pm@vger.kernel.org, linux-usb@vger.kernel.org, mchehab@kernel.org, pavel@kernel.org, rafael@kernel.org References: <20260729075655.1187692-1-tuhaowen@uniontech.com> <0e22e9d4-da39-4d3f-9492-5c74295be312@rowland.harvard.edu> Content-Language: en-US From: Oliver Neukum In-Reply-To: <0e22e9d4-da39-4d3f-9492-5c74295be312@rowland.harvard.edu> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 29.07.26 16:08, Alan Stern wrote: > You're missing an important fact: If something goes wrong during the > hibernation transition (for example, if the kernel's memory image can't > be stored to disk) then there will be no RESTORE phase. Following the > THAW phase, the system will return to normal operation. Right, but that does not need to mean that the driver has to be operational at the THAW phase. It has to be operational before userland is unfrozen again at the latest. The difficulty how the driver learns that the system will not power down remains to be solved. > For this reason, during THAW drivers must not assume that the system is > about to power down. True. For this reason the patch introduces a notifier queue. Now, that you make me think about that it seems to be inelegant, as this throws away the proper order of the device tree. It seems to me that we should bite the bullet and go for the big solution: Split the THAW phase in two, like a THAW_WRITEOUT and an optional THAW_BAILOUT that is called only when the system does not power down. Regards Oliver