Re: [PATCH] Input: usbtouchscreen - initialize eGalax devices

On Fri, 31 Aug 2012, Dmitry Torokhov wrote:

quoted

quoted

+		/* Send a "check active" packet. The response will be read
+		 * later and ignored. */
+		ret = usb_control_msg(udev, usb_rcvctrlpipe(udev, 0),
+				      0,
+				      USB_DIR_OUT | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
+				      0, 0, "\x0A\x01A", 0,

   You probably can't send data from the .const section (as well as off the
stack) -- they can be DMA'ed and there'll be issues with cache consistency on
non-x86 arches. You should allocate the data with kmalloc().
   Although, on the second thought, maybe I'm wrong in this case... not really
sure about sending -- receiving (to the .data section) could certainly be harmful...

Hmm, do we actually send anything here? The "size" passed to
usb_control_msg() is 0 so I don't think we use that data at all...

Good point.  Perhaps the 0 is a typo, in which case data does get sent
and the buffer must be kmalloc'ed.  If the 0 is correct then the buffer
should be NULL, not "\x0A\x01A" (and what's the purpose of the leading
'0' in the second byte?).

In addition, although the bRequestType specifies USB_DIR_OUT, the pipe
value is usb_rcvctrlpipe.  Is this transfer meant to be IN or OUT?

Alan Stern

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