linux-kernel - Re: [PATCH v3] char: xillybus: Check endpoint type at probe time

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Message-ID: <6294DED6.70904@gmail.com>
Date:   Mon, 30 May 2022 18:12:22 +0300
From:   Eli Billauer <eli.billauer@...il.com>
To:     Zheyu Ma <zheyuma97@...il.com>
CC:     arnd@...db.de, gregkh@...uxfoundation.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] char: xillybus: Check endpoint type at probe time

On 29/05/22 09:58, Zheyu Ma wrote:
>   static int xillyusb_setup_base_eps(struct xillyusb_dev *xdev)
>   {
> +	int ret;
> +	struct usb_endpoint_descriptor *in, *out;
> +
> +	ret = usb_find_common_endpoints(xdev->intf->cur_altsetting,&in,&out, NULL, NULL);
> +	if (ret)
> +		return ret;
> +
> +	if (in->bEndpointAddress != (IN_EP_NUM | USB_DIR_IN) ||
> +		out->bEndpointAddress != (MSG_EP_NUM | USB_DIR_OUT))
> +		return -EINVAL;
> +
>    
As far as I understand, this finds the first BULK endpoints in both 
directions, and verifies that their addresses are MSG_EP_NUM and 
IN_EP_NUM. Because both of these happen to equal 1, I suppose this 
indeed checks the right thing. But am I right that this won't work if 
either MSG_EP_NUM or IN_EP_NUM have a value that isn't 1? Not that I 
think that will ever happen, but still.

> +static int xillyusb_check_endpoint(struct xillyusb_dev *xdev, u8 addr)
> +{
> +	int i;
> +	struct usb_host_interface *if_desc = xdev->intf->altsetting;
> +
> +	for (i = 0; i<  if_desc->desc.bNumEndpoints; i++) {
> +		struct usb_endpoint_descriptor *ep =&if_desc->endpoint[i].desc;
> +
> +		if (ep->bEndpointAddress == addr&&  usb_endpoint_is_bulk_out(ep))
> +			return 0;
> +	}
> +
> +	return -EINVAL;
> +}
> +
>
>    
Given that you've added this function, why isn't it used in 
xillyusb_setup_base_eps()?

Thanks,
    Eli