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Tue, 01 Jul 2025 15:56:27 -0700 (PDT) Received: from [192.168.1.14] ([38.175.170.29]) by smtp.gmail.com with ESMTPSA id 8926c6da1cb9f-50204a537b3sm2634438173.69.2025.07.01.15.56.26 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 01 Jul 2025 15:56:27 -0700 (PDT) Message-ID: Date: Tue, 1 Jul 2025 16:56:26 -0600 Precedence: bulk X-Mailing-List: linux-usb@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] usbip: convert to use faux_device To: Zongmin Zhou , Greg KH Cc: shuah@kernel.org, valentina.manea.m@gmail.com, i@zenithal.me, linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org, zhouzongmin@kylinos.cn, Shuah Khan References: <2a327b520760271471717fff9b222cdc34967489.1746662386.git.zhouzongmin@kylinos.cn> <20250604065410.76069-1-min_halo@163.com> <2025061926-paycheck-footnote-a2b8@gregkh> <2025062010-hardiness-flashily-cb0f@gregkh> <9d95bb75-586c-48dc-9e34-432cc13fd99f@163.com> <2025062004-navy-emboss-4743@gregkh> <2e0bbc5a-e74a-4fb5-884c-686dbaf99caf@linuxfoundation.org> <48ab511e-2847-4daa-98de-a234b8584b78@163.com> Content-Language: en-US From: Shuah Khan In-Reply-To: <48ab511e-2847-4daa-98de-a234b8584b78@163.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 6/23/25 21:21, Zongmin Zhou wrote: > > On 2025/6/21 01:26, Shuah Khan wrote: >> On 6/20/25 03:27, Greg KH wrote: >>> On Fri, Jun 20, 2025 at 05:19:33PM +0800, Zongmin Zhou wrote: >>>> >>>> On 2025/6/20 12:29, Greg KH wrote: >>>>> On Fri, Jun 20, 2025 at 10:16:16AM +0800, Zongmin Zhou wrote: >>>>>> On 2025/6/19 19:01, Greg KH wrote: >>>>>>> On Wed, Jun 04, 2025 at 02:54:10PM +0800, Zongmin Zhou wrote: >>>>>>>> From: Zongmin Zhou >>>>>>>> >>>>>>>> The vhci driver does not need to create a platform device, >>>>>>>> it only did so because it was simple to do that in order to >>>>>>>> get a place in sysfs to hang some device-specific attributes. >>>>>>>> Now the faux device interface is more appropriate,change it >>>>>>>> over to use the faux bus instead. >>>>>>>> >>>>>>>> Signed-off-by: Zongmin Zhou >>>>>>>> --- >>>>>>>> Changes in v2: >>>>>>>> - don't change faux create api,just call probe on vhci_hcd_init. >>>>>>>> >>>>>>>>     drivers/usb/usbip/vhci.h             |  4 +- >>>>>>>>     drivers/usb/usbip/vhci_hcd.c         | 86 +++++++++++----------------- >>>>>>>>     drivers/usb/usbip/vhci_sysfs.c       | 68 +++++++++++----------- >>>>>>>>     tools/usb/usbip/libsrc/vhci_driver.h |  2 +- >>>>>>>>     4 files changed, 72 insertions(+), 88 deletions(-) >>>>>>> I get the following build errors from this patch: >>>>>>> >>>>>>> drivers/usb/usbip/vhci_hcd.c:1462:12: error: ‘vhci_hcd_resume’ defined but not used [-Werror=unused-function] >>>>>>>     1462 | static int vhci_hcd_resume(struct faux_device *fdev) >>>>>>>          |            ^~~~~~~~~~~~~~~ >>>>>>> drivers/usb/usbip/vhci_hcd.c:1418:12: error: ‘vhci_hcd_suspend’ defined but not used [-Werror=unused-function] >>>>>>>     1418 | static int vhci_hcd_suspend(struct faux_device *fdev, pm_message_t state) >>>>>>>          |            ^~~~~~~~~~~~~~~~ >>>>>>> cc1: all warnings being treated as errors >>>>>>> >>>>>>> Are you sure you tested this? >>>>>> I apologize for not enabling -Werror, which resulted in missing this error >>>>>> warning. >>>>>> I have tested usbip feature use the new patch,but not test system >>>>>> suspend/resume. >>>>>> The faux bus type don't add pm function,and vhci-hcd driver can't register >>>>>> it. >>>>>> Maybe have to add suspend/resume for it.like below: >>>>>> static const struct bus_type faux_bus_type = { >>>>>>       .name        = "faux", >>>>>>       .match        = faux_match, >>>>>>       .probe        = faux_probe, >>>>>>       .remove        = faux_remove, >>>>>>       .resume     = faux_resume, >>>>>>       .suspend    = faux_suspend, >>>>>> }; >>>>>> >>>>>> Is that right? >>>>>> Your expertise would be greatly valued. >>>>> As this is not real hardware, why do you need the suspend/resume >>>>> callbacks at all?  What is happening here that requires them? >>>> @greg, >>>> The vhci_hcd_suspend/vhci_hcd_resume interfaces are not designed for this >>>> faux device, but rather to >>>> manipulate the HCD_FLAG_HW_ACCESSIBLE bit in the hcd flags associated with >>>> the faux device. >>>> For example: >>>> During system standby: clear_bit(HCD_FLAG_HW_ACCESSIBLE, &hcd->flags) >>>> During system wakeup: set_bit(HCD_FLAG_HW_ACCESSIBLE, &hcd->flags) >>>> >>>> Previously, these two functions were registered through platform_driver, >>>> but faux bus does not have the relevant interface, so they were not called, >>>> resulting in this compilation warning error. >>>> >>>> This raises the question: Should the faux bus implement PM-related >>>> interface? >>>> I'm uncertain whether these functions are essential for the vhci-hcd driver >>>> or if they can be safely removed. >>>> >>>> However, during system standby/wakeup tests with remote USB devices bound to >>>> the vhci-hcd driver, >>>> I observed consistent failure scenarios across both the original platform >>>> bus and faux bus patch implementations. >> >> suspend and resume hooks have been in the code from beginning >> in the CONFIG_PM path. The original authors are skeptical about >> what should happen during suspend" >> >> /* what should happen for USB/IP under suspend/resume? */ >> suspend hook checks for active connections and sends EBBUSY >> back to pm core. >> >> Active connection means any of the ports are in USB_PORT_STAT_CONNECTION >> state. So as long as there are active connections between vhci client >> and the host, suspend won't work. So we really don't know what happens >> to the active connections if there are no suspend/resume hooks. >> >> If there are no active connections, then it will clear the HCD_FLAG_HW_ACCESSIBLE >> bit and returns to pm core to continue with suspend. >> >> resume sets the HCD_FLAG_HW_ACCESSIBLE flag to indicate hardware is accessible >> and initiates port status poll. >> >> - suspend hook prevents suspend >> >> With faux device since there is no suspend and resume hook, I would expect >> these hooks are not a factor in suspend and resume. >> >> vhci_hcd is a special case virtual driver as it is a proxy for controlling >> hardware on the host. >> >> Zongmin, >> >> Do suspend/resume work when vhci_hcd is not loaded? >> What happens when when system suspends and resumes with faux device? >> Can you send me dmesg logs and pm logs? >> > Hi Greg,shuah > > Yes, system with vhci_hcd unload or just load vhci_hcd driver > without usbip devices bound to vhci_hcd,system suspend/resume worked well. > Some logs for you. Sorry for the delay. I was at a conference last week. Thank you for sending these logs. > 1.system with vhci_hcd driver load,but don't bound any usbip devices to vhci_hcd,suspend/resume worked well. > see dmesg-faux bus-load.log > > 2.usbip device bound to vhci_hcd,and do system suspend action,suspend/resume worked failed. > I observed two distinct failure scenario: > Scenario 1: System failed to enter suspend state,and will auto resume; > the log for use platform bus: > dmesg-platform bus-device bound-auto resume.log This is clear from the suspend hook in the vhci_hcd. When it returns EBUSY, suspend will fail and move to auto resume. > the log for use faux bus: > dmesg-faux bus-device bound-auto resume.log It is good that the behavior is same with faux bus even though suspend hook isn't called. I will take a look at the log. > > Scenario 2: System resume failed with black screen freeze,a forced restart of the machine is require. > the log for use platform bus: > dmesg-platform bus-device bound-black screen.log > the log for use faux bus: > dmesg-faux bus-device bound-black screen.log That is bad. When does this happen? Is there a difference in configuration? The behavior same for platform bus and faux bus. Sounds like an existing problem that needs to be debugged separately. I will take a look at all these logs and get back to you in a day or two. thanks, -- Shuah