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[83.28.47.76]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-498365cbfc6sm917789f8f.41.2026.11.09.12.34.41 (version=TLS1_2 cipher=AES128-SHA bits=128/128); Mon, 09 Nov 2026 12:34:42 -0800 (PST) Date: Mon, 9 Nov 2026 21:34:37 +0100 From: Michal Pecio To: Alan Stern Cc: Pengfei Lv , gregkh@linuxfoundation.org, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, xuhaiyang5@hisilicon.com, xuetao09@huawei.com, caiyadong@huawei.com, suzhuangluan@hisilicon.com Subject: Re: [PATCH v3] usb: core: hub: Re-guess ep0 maxpacket size after reset Message-ID: <20261109213437.5c693895.michal.pecio@gmail.com> In-Reply-To: <3daf18d4-4936-4ed7-8846-b67f1664be13@rowland.harvard.edu> References: <20261106031625.1824732-1-lvpengfei20@huawei.com> <20261109093935.2634235-1-lvpengfei20@huawei.com> <3daf18d4-4936-4ed7-8846-b67f1664be13@rowland.harvard.edu> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Mon, 9 Nov 2026 11:05:30 -0500, Alan Stern wrote: > > diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c > > index 199d3f535a89..d86bbba1457c 100644 > > --- a/drivers/usb/core/hub.c > > +++ b/drivers/usb/core/hub.c > > @@ -4969,31 +4969,29 @@ hub_port_init(struct usb_hub *hub, struct usb_device *udev, int port1, > > } > > oldspeed = udev->speed; > > > > - if (initial) { > > - /* USB 2.0 section 5.5.3 talks about ep0 maxpacket ... > > - * it's fixed size except for full speed devices. > > + /* USB 2.0 section 5.5.3 talks about ep0 maxpacket ... > > + * it's fixed size except for full speed devices. > > + */ > > + switch (udev->speed) { > > + case USB_SPEED_SUPER_PLUS: > > + case USB_SPEED_SUPER: > > + udev->ep0.desc.wMaxPacketSize = cpu_to_le16(512); > > + break; > > + case USB_SPEED_HIGH: /* fixed at 64 */ > > + udev->ep0.desc.wMaxPacketSize = cpu_to_le16(64); > > + break; > > + case USB_SPEED_FULL: /* 8, 16, 32, or 64 */ > > + /* to determine the ep0 maxpacket size, try to read > > + * the device descriptor to get bMaxPacketSize0 and > > + * then correct our initial guess. > > */ > > - switch (udev->speed) { > > - case USB_SPEED_SUPER_PLUS: > > - case USB_SPEED_SUPER: > > - udev->ep0.desc.wMaxPacketSize = cpu_to_le16(512); > > - break; > > - case USB_SPEED_HIGH: /* fixed at 64 */ > > - udev->ep0.desc.wMaxPacketSize = cpu_to_le16(64); > > - break; > > - case USB_SPEED_FULL: /* 8, 16, 32, or 64 */ > > - /* to determine the ep0 maxpacket size, try to read > > - * the device descriptor to get bMaxPacketSize0 and > > - * then correct our initial guess. > > - */ > > - udev->ep0.desc.wMaxPacketSize = cpu_to_le16(64); > > - break; > > - case USB_SPEED_LOW: /* fixed at 8 */ > > - udev->ep0.desc.wMaxPacketSize = cpu_to_le16(8); > > - break; > > - default: > > - goto fail; > > - } > > + udev->ep0.desc.wMaxPacketSize = cpu_to_le16(64); > > + break; > > + case USB_SPEED_LOW: /* fixed at 8 */ > > + udev->ep0.desc.wMaxPacketSize = cpu_to_le16(8); > > + break; > > + default: > > + goto fail; > > } > > The usb_ep0_reinit() call belongs here, right after > udev->ep0.desc.wMaxPacketSize is set. > > > > > speed = usb_speed_string(udev->speed); > > @@ -5062,6 +5060,9 @@ hub_port_init(struct usb_hub *hub, struct usb_device *udev, int port1, > > goto fail; > > } > > > > + /* Sync the guessed ep0 maxpacket size to hardware if needed */ > > + usb_ep0_reinit(udev); > > Not here. And not inside the retry loop -- ep0_reinit should be > called only once since the maxpacket value is changed only once. Sashiko pointed out that xhci-hcd may not perform ep0_reinit() properly until address_device() or enable_device() is called. So it's either this kludge, or dependency on an xhci-hcd patch which didn't exist until today: https://lore.kernel.org/linux-usb/20261109112846.04bfeb0f.michal.pecio@gmail.com/ Regards, Michal