linux-kernel - Re: [PATCH] enable usb control message with class specific request

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Message-ID: <20110923090550.43ec1fd1@horus>
Date:	Fri, 23 Sep 2011 09:05:50 +0200
From:	Matthias Dellweg <2500@....de>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	Greg Kroah-Hartman <gregkh@...e.de>,
	Vasiliy Kulikov <segooon@...il.com>,
	Michal Sojka <sojkam1@....cvut.cz>,
	Arnd Bergmann <arnd@...db.de>, <linux-usb@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] enable usb control message with class specific request

Am Thu, 22 Sep 2011 23:56:56 +0200
schrieb Matthias Dellweg <2500@....de>:

> +       if ((requesttype == 0xa1) && (request == 0x00)
> +        && (usb_find_alt_setting(ps->dev->actconfig, index >> 8,
> index & 0xff)
> +        ->desc.bInterfaceClass == USB_CLASS_PRINTER))
> +               index >>= 8;

I just woke up and realised this is a very bad idea if there is no such
setting...
So here's the next version I'd like to propose for comments:

diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c
index 37518df..d2efc97 100644
--- a/drivers/usb/core/devio.c
+++ b/drivers/usb/core/devio.c
@@ -607,9 +607,10 @@ static int findintfep(struct usb_device *dev, unsigned int ep)
 }
 
 static int check_ctrlrecip(struct dev_state *ps, unsigned int requesttype,
-                          unsigned int index)
+                          unsigned int request, unsigned int index)
 {
        int ret = 0;
+       struct usb_host_interface *alt_setting;
 
        if (ps->dev->state != USB_STATE_UNAUTHENTICATED
         && ps->dev->state != USB_STATE_ADDRESS
@@ -618,6 +619,15 @@ static int check_ctrlrecip(struct dev_state *ps, unsigned int requesttype,
        if (USB_TYPE_VENDOR == (USB_TYPE_MASK & requesttype))
                return 0;
 
+       /* check for the special corner case 'get_device_id' in the printer class specification,
+        * where wIndex is (configuration << 8 | altsetting) */
+       if ((requesttype == 0xa1) && (request == 0x00))
+       {
+               alt_setting = usb_find_alt_setting(ps->dev->actconfig, index >> 8, index & 0xff);
+               if (alt_setting && (alt_setting->desc.bInterfaceClass == USB_CLASS_PRINTER))
+                       index >>= 8;
+       }
+
        index &= 0xff;
        switch (requesttype & USB_RECIP_MASK) {
        case USB_RECIP_ENDPOINT:
@@ -770,7 +780,7 @@ static int proc_control(struct dev_state *ps, void __user *arg)
 
        if (copy_from_user(&ctrl, arg, sizeof(ctrl)))
                return -EFAULT;
-       ret = check_ctrlrecip(ps, ctrl.bRequestType, ctrl.wIndex);
+       ret = check_ctrlrecip(ps, ctrl.bRequestType, ctrl.bRequest, ctrl.wIndex);
        if (ret)
                return ret;
        wLength = ctrl.wLength;         /* To suppress 64k PAGE_SIZE warning */
@@ -1100,7 +1110,7 @@ static int proc_do_submiturb(struct dev_state *ps, struct usbdevfs_urb *uurb,
                        kfree(dr);
                        return -EINVAL;
                }
-               ret = check_ctrlrecip(ps, dr->bRequestType,
+               ret = check_ctrlrecip(ps, dr->bRequestType, dr->bRequest,
                                      le16_to_cpup(&dr->wIndex));
                if (ret) {
                        kfree(dr);
--
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