Re: [PATCH v3 2/6] usb: xhci: Set up endpoints for the first 2 interfaces

[Heinrich Schuchardt <heinrich.schuchardt@canonical.com>]

On 3/22/24 08:47, Janne Grunau via B4 Relay wrote:
> From: Janne Grunau <j@jannau.net>
> 
> The xhci driver currently only does the necessary initialization for
> endpoints found in the first interface descriptor. Apple USB keyboards
> (released 2021) use the second interface descriptor for the HID keyboard
> boot protocol. To allow USB drivers to use endpoints from other
> interface descriptors the xhci driver needs to ensure these endpoints
> are initialized as well.
> Use USB_MAX_ACTIVE_INTERFACES to control how many interface descriptors
> are considered during endpoint initialisation.
> For now define it to 2 as that is sufficient for supporting the Apple
> keyboards.
> 
> Reviewed-by: Marek Vasut <marex@denx.de>
> Reviewed-by: Neal Gompa <neal@gompa.dev>
> Signed-off-by: Janne Grunau <j@jannau.net>
> ---
>   drivers/usb/host/xhci.c | 31 +++++++++++++++++++------------
>   include/usb.h           |  6 ++++++
>   2 files changed, 25 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
> index 534c4b973f..741e186ee0 100644
> --- a/drivers/usb/host/xhci.c
> +++ b/drivers/usb/host/xhci.c
> @@ -606,24 +606,28 @@ static int xhci_set_configuration(struct usb_device *udev)
>   	int slot_id = udev->slot_id;
>   	struct xhci_virt_device *virt_dev = ctrl->devs[slot_id];
>   	struct usb_interface *ifdesc;
> +	unsigned int ifnum;
> +	unsigned int max_ifnum = min((unsigned int)USB_MAX_ACTIVE_INTERFACES,

no_of_if being of type u8 limits the number of interfaces to 255. 
Introducing USB_MAX_ACTIVE_INTERFACES limit us to the first two 
interfaces. Is this really needed? Handling all interface would avoid 
the introduction of artificial limitations which may hit us on the next 
device.

Best regards

Heinrich

> +				     (unsigned int)udev->config.no_of_if);
>   
>   	out_ctx = virt_dev->out_ctx;
>   	in_ctx = virt_dev->in_ctx;
>   
> -	num_of_ep = udev->config.if_desc[0].no_of_ep;
> -	ifdesc = &udev->config.if_desc[0];
> -
>   	ctrl_ctx = xhci_get_input_control_ctx(in_ctx);
>   	/* Initialize the input context control */
>   	ctrl_ctx->add_flags = cpu_to_le32(SLOT_FLAG);
>   	ctrl_ctx->drop_flags = 0;
>   
> -	/* EP_FLAG gives values 1 & 4 for EP1OUT and EP2IN */
> -	for (cur_ep = 0; cur_ep < num_of_ep; cur_ep++) {
> -		ep_flag = xhci_get_ep_index(&ifdesc->ep_desc[cur_ep]);
> -		ctrl_ctx->add_flags |= cpu_to_le32(1 << (ep_flag + 1));
> -		if (max_ep_flag < ep_flag)
> -			max_ep_flag = ep_flag;
> +	for (ifnum = 0; ifnum < max_ifnum; ifnum++) {
> +		ifdesc = &udev->config.if_desc[ifnum];
> +		num_of_ep = ifdesc->no_of_ep;
> +		/* EP_FLAG gives values 1 & 4 for EP1OUT and EP2IN */
> +		for (cur_ep = 0; cur_ep < num_of_ep; cur_ep++) {
> +			ep_flag = xhci_get_ep_index(&ifdesc->ep_desc[cur_ep]);
> +			ctrl_ctx->add_flags |= cpu_to_le32(1 << (ep_flag + 1));
> +			if (max_ep_flag < ep_flag)
> +				max_ep_flag = ep_flag;
> +		}
>   	}
>   
>   	xhci_inval_cache((uintptr_t)out_ctx->bytes, out_ctx->size);
> @@ -637,9 +641,12 @@ static int xhci_set_configuration(struct usb_device *udev)
>   	xhci_endpoint_copy(ctrl, in_ctx, out_ctx, 0);
>   
>   	/* filling up ep contexts */
> -	err = xhci_init_ep_contexts_if(udev, ctrl, virt_dev, ifdesc);
> -	if (err < 0)
> -		return err;
> +	for (ifnum = 0; ifnum < max_ifnum; ifnum++) {
> +		ifdesc = &udev->config.if_desc[ifnum];
> +		err = xhci_init_ep_contexts_if(udev, ctrl, virt_dev, ifdesc);
> +		if (err < 0)
> +			return err;
> +	}
>   
>   	return xhci_configure_endpoints(udev, false);
>   }
> diff --git a/include/usb.h b/include/usb.h
> index 09e3f0cb30..3aafdc8bfd 100644
> --- a/include/usb.h
> +++ b/include/usb.h
> @@ -49,6 +49,12 @@ extern bool usb_started; /* flag for the started/stopped USB status */
>    */
>   #define USB_TIMEOUT_MS(pipe) (usb_pipebulk(pipe) ? 5000 : 1000)
>   
> +/*
> + * The xhcd hcd driver prepares only a limited number interfaces / endpoints.
> + * Define this limit so that drivers do not exceed it.
> + */
> +#define USB_MAX_ACTIVE_INTERFACES	2
> +
>   /* device request (setup) */
>   struct devrequest {
>   	__u8	requesttype;
>