Re: [PATCH v2 2/3] usb: gadget: composite: Support eUSB2v2 bulk MPS update request

[Selvarasu Ganesan <selvarasu.g@samsung.com>]

On 8/26/2026 4:54 PM, Pawel Laszczak via B4 Relay wrote:
> From: Pawel Laszczak <pawell@cadence.com>
>
> Add support for eUSB2v2 1024-byte Bulk MPS negotiation to the Gadget
> Composite framework.
>
> If 'gadget->is_eusb2v2' is set, force bcdUSB to 0x0230 and bMaxPacketSize0
> to 64 bytes. Handle the USB_DEVICE_BULK_MAX_PACKET_UPDATE feature request
> by introducing eusb2_update_mps_bulk(), which dynamically updates the
> wMaxPacketSize of all HS Bulk endpoint descriptors to 1024 bytes before
> the device is configured.
>
> Signed-off-by: Pawel Laszczak <pawell@cadence.com>
> ---
> Changes in v2:
> - composite.c: CLEAR_FEATURE(BULK_MAX_PACKET_UPDATE) is not defined in the
>    eUSB2v2 spec; stall it instead of incorrectly setting 1024-byte mode.
> - restore MPS in __composite_disconnect
> ---
>   drivers/usb/gadget/composite.c | 68 ++++++++++++++++++++++++++++++++++++++----
>   include/linux/usb/gadget.h     |  2 ++
>   2 files changed, 64 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/usb/gadget/composite.c b/drivers/usb/gadget/composite.c
> index dc3664374596..f0246e25f2b5 100644
> --- a/drivers/usb/gadget/composite.c
> +++ b/drivers/usb/gadget/composite.c
> @@ -924,6 +924,48 @@ static void device_qual(struct usb_composite_dev *cdev)
>   }
>   
>   /*-------------------------------------------------------------------------*/
> +static void eusb2_update_ep_mps(struct usb_descriptor_header *header, __le16 mps)
> +{
> +	struct usb_endpoint_descriptor *epd;
> +
> +	if (header->bDescriptorType != USB_DT_ENDPOINT)
> +		return;
> +
> +	epd = (void *)header;
> +	if (usb_endpoint_xfer_bulk(epd))
> +		epd->wMaxPacketSize = mps;
> +}
> +
> +static int eusb2_update_mps_bulk(struct usb_composite_dev *cdev, bool set)
> +{
> +	__le16 mps = cpu_to_le16(set ? 1024 : 512);
> +	struct usb_gadget *gadget = cdev->gadget;
> +	struct usb_configuration *config;
> +	struct usb_function *f;
> +
> +	if (!gadget->is_eusb2v2)
> +		return -EINVAL;
> +
> +	if (set && gadget->state >= USB_STATE_CONFIGURED)
> +		return -EINVAL;
> +
> +	list_for_each_entry(config, &cdev->configs, list) {
> +		if (!config->highspeed)
> +			continue;
> +
> +		list_for_each_entry(f, &config->functions, list) {
> +			struct usb_descriptor_header **desc = f->hs_descriptors;
> +
> +			if (!desc)
> +				continue;
> +
> +			for (; *desc; desc++)
> +				eusb2_update_ep_mps(*desc, mps);
> +		}
> +	}
> +
> +	return 0;
> +}
>   
>   static void reset_config(struct usb_composite_dev *cdev)
>   {
> @@ -971,8 +1013,10 @@ static int set_config(struct usb_composite_dev *cdev,
>   		if (result < 0)
>   			goto done;
>   	} else { /* Zero configuration value - need to reset the config */
> -		if (cdev->config)
> +		if (cdev->config) {
>   			reset_config(cdev);
> +			eusb2_update_mps_bulk(cdev, false);
> +		}
>   		result = 0;
>   	}
>   
> @@ -1807,7 +1851,11 @@ composite_setup(struct usb_gadget *gadget, const struct usb_ctrlrequest *ctrl)
>   				count_configs(cdev, USB_DT_DEVICE);
>   			cdev->desc.bMaxPacketSize0 =
>   				cdev->gadget->ep0->maxpacket;
> -			if (gadget_is_superspeed(gadget)) {
> +
> +			if (gadget->is_eusb2v2) {
> +				cdev->desc.bcdUSB = cpu_to_le16(0x0230);
> +				cdev->desc.bMaxPacketSize0 = 64;
> +			} else if (gadget_is_superspeed(gadget)) {
>   				if (gadget->speed >= USB_SPEED_SUPER) {
>   					cdev->desc.bcdUSB = cpu_to_le16(0x0320);
>   					cdev->desc.bMaxPacketSize0 = 9;
> @@ -2005,12 +2053,19 @@ composite_setup(struct usb_gadget *gadget, const struct usb_ctrlrequest *ctrl)
>   	 */
>   	case USB_REQ_CLEAR_FEATURE:
>   	case USB_REQ_SET_FEATURE:
> -		if (!gadget_is_superspeed(gadget))
> -			goto unknown;
> -		if (ctrl->bRequestType != (USB_DIR_OUT | USB_RECIP_INTERFACE))
> -			goto unknown;
>   		switch (w_value) {
> +		case USB_DEVICE_BULK_MAX_PACKET_UPDATE:
> +			if (ctrl->bRequestType != (USB_DIR_OUT | USB_RECIP_DEVICE))
> +				goto unknown;
> +			if (ctrl->bRequest != USB_REQ_SET_FEATURE)
> +				goto unknown;
> +			value = eusb2_update_mps_bulk(cdev, true);
Here both USB_REQ_CLEAR_FEATURE and USB_REQ_SET_FEATURE fall through to 
the same switch, and USB_DEVICE_BULK_MAX_PACKET_UPDATE unconditionally 
calls eusb2_update_mps_bulk(cdev, true) regardless of which request type 
was received.

The CLEAR_FEATURE may request should revert the MPS back to the default 
by calling eusb2_update_mps_bulk(cdev, false), but instead it performs 
the same action as SET_FEATURE.

Is this required distinguished using ctrl->bRequest to check whether 
this is a SET or CLEAR operation?


Thanks,
Selva
> +			break;
>   		case USB_INTRF_FUNC_SUSPEND:
> +			if (!gadget_is_superspeed(gadget))
> +				goto unknown;
> +			if (ctrl->bRequestType != (USB_DIR_OUT | USB_RECIP_INTERFACE))
> +				goto unknown;
>   			if (!cdev->config || intf >= MAX_CONFIG_INTERFACES)
>   				break;
>   			f = cdev->config->interface[intf];
> @@ -2293,6 +2348,7 @@ static void __composite_disconnect(struct usb_gadget *gadget)
>   	 * disconnect callbacks?
>   	 */
>   	spin_lock_irqsave(&cdev->lock, flags);
> +	eusb2_update_mps_bulk(cdev, false);
>   	cdev->suspended = 0;
>   	if (cdev->config)
>   		reset_config(cdev);
> diff --git a/include/linux/usb/gadget.h b/include/linux/usb/gadget.h
> index 8285b19a25e0..3c554fe95f87 100644
> --- a/include/linux/usb/gadget.h
> +++ b/include/linux/usb/gadget.h
> @@ -420,6 +420,7 @@ struct usb_gadget_ops {
>    * @wakeup_armed: True if gadget is armed by the host for remote wakeup.
>    * @irq: the interrupt number for device controller.
>    * @id_number: a unique ID number for ensuring that gadget names are distinct
> + * @is_eusb2v2: True if controller is Embedded usb2.
>    *
>    * Gadgets have a mostly-portable "gadget driver" implementing device
>    * functions, handling all usb configurations and interfaces.  Gadget
> @@ -483,6 +484,7 @@ struct usb_gadget {
>   	unsigned			lpm_capable:1;
>   	unsigned			wakeup_capable:1;
>   	unsigned			wakeup_armed:1;
> +	unsigned			is_eusb2v2:1;
>   	int				irq;
>   	int				id_number;
>   };
>