usb: host: allow partially read device descriptor

To determine bMaxPacketSize0, which is unknown after the reset.

Signed-off-by: Johann Fischer <[email protected]>

Author: jfischer-no

subsys/usb/host/usbh_ch9.c

@@ -116,10 +116,11 @@ int usbh_req_desc(struct usb_device *const udev,
 }
 
 int usbh_req_desc_dev(struct usb_device *const udev,
+		      const uint16_t len,
 		      struct usb_device_descriptor *const desc)
 {
 	const uint8_t type = USB_DESC_DEVICE;
-	const uint16_t wLength = sizeof(struct usb_device_descriptor);
+	const uint16_t wLength = MIN(len, sizeof(struct usb_device_descriptor));
 	struct net_buf *buf;
 	int ret;
 

subsys/usb/host/usbh_ch9.h

@@ -27,6 +27,7 @@ int usbh_req_desc(struct usb_device *const udev,
 		  struct net_buf *const data);
 
 int usbh_req_desc_dev(struct usb_device *const udev,
+		      const uint16_t len,
 		      struct usb_device_descriptor *const dev);
 
 int usbh_req_desc_cfg(struct usb_device *const udev,

subsys/usb/host/usbh_shell.c

@@ -188,7 +188,7 @@ static int cmd_desc_device(const struct shell *sh,
 	struct usb_device_descriptor desc;
 	int err;
 
-	err = usbh_req_desc_dev(udev, &desc);
+	err = usbh_req_desc_dev(udev, sizeof(desc), &desc);
 	if (err) {
 		shell_print(sh, "host: Failed to request device descriptor");
 	} else {