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

Hi Dmitry,

On Fri, Aug 31, 2012 at 04:10:47PM -0700, Dmitry Torokhov wrote:

On Fri, Aug 31, 2012 at 06:53:53PM -0400, Forest Bond wrote:

quoted

Hi,

On Fri, Aug 31, 2012 at 04:04:58PM -0400, Alan Stern wrote:

quoted

On Fri, 31 Aug 2012, Dmitry Torokhov wrote:

quoted

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?

Thanks again to all for the review.  My theory for why the previous patch worked
in spite of its wrongness is that the device actually switches modes when it
receives a control message with USB_TYPE_VENDOR even though the documentation
suggests an actual diagnostic packet must be received.

Does this (untested) patch look more reasonable?

Yes, but we still need it tested, please.

Great, I'll test it later this evening when I am back in front of the hardware
and follow up with a properly submitted patch.

Thanks again,
Forest
-- 
Forest Bond
http://www.alittletooquiet.net
http://www.rapidrollout.com

From: Forest Bond <redacted>

Certain eGalax devices expose an interface with class HID and protocol
None.  Some work with usbhid and some work with usbtouchscreen, but
there is no easy way to differentiate.  Sending an eGalax diagnostic
packet seems to kick them all into using the right protocol for
usbtouchscreen, so we can continue to bind them all there (as opposed to
handing some off to usbhid).

This fixes a regression for devices that were claimed by (and worked
with) usbhid prior to commit 139ebe8dc80dd74cb2ac9f5603d18fbf5cff049f
("Input: usbtouchscreen - fix eGalax HID ignoring"), which made
usbtouchscreen claim them instead.  With this patch they will still be
claimed by usbtouchscreen, but they will actually report events
usbtouchscreen can understand.  Note that these devices will be limited
to the usbtouchscreen feature set so e.g. dual touch features are not
supported.

I have the distinct pleasure of needing to support devices of both types
and have tested accordingly.

Signed-off-by: Forest Bond <redacted>
---
 drivers/input/touchscreen/usbtouchscreen.c |   36 ++++++++++++++++++++++++++++
 1 files changed, 36 insertions(+), 0 deletions(-)

diff --git a/drivers/input/touchscreen/usbtouchscreen.c b/drivers/input/touchscreen/usbtouchscreen.c
index e32709e..64b4b17 100644
--- a/drivers/input/touchscreen/usbtouchscreen.c
+++ b/drivers/input/touchscreen/usbtouchscreen.c

@@ -304,6 +304,41 @@ static int e2i_read_data(struct usbtouch_usb *dev, unsigned char *pkt)
 #define EGALAX_PKT_TYPE_REPT		0x80
 #define EGALAX_PKT_TYPE_DIAG		0x0A
 
+static int egalax_init(struct usbtouch_usb *usbtouch)
+{
+	int ret, i;
+	unsigned char *buf;
+	struct usb_device *udev = interface_to_usbdev(usbtouch->interface);
+
+	/* An eGalax diagnostic packet kicks the device into using the right
+	 * protocol.  We send a "check active" packet.  The response will be
+	 * read later and ignored.
+	 */
+
+	buf = kmalloc(3, GFP_KERNEL);
+	buf[0] = EGALAX_PKT_TYPE_DIAG;
+	buf[1] = 1;	/* length */
+	buf[2] = 'A';	/* command - check active */
+
+	for (i = 0; i < 3; i++) {
+		ret = usb_control_msg(udev, usb_sndctrlpipe(udev, 0),
+				      0,
+				      USB_DIR_OUT | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
+				      0, 0, buf, 3,
+				      USB_CTRL_SET_TIMEOUT);
+		if (ret >= 0) {
+			ret = 0;
+			break;
+		}
+		if (ret != -EPIPE)
+			break;
+	}
+
+	kfree(buf);
+
+	return ret;
+}
+
 static int egalax_read_data(struct usbtouch_usb *dev, unsigned char *pkt)
 {
 	if ((pkt[0] & EGALAX_PKT_TYPE_MASK) != EGALAX_PKT_TYPE_REPT)

@@ -1056,6 +1091,7 @@ static struct usbtouch_device_info usbtouch_dev_info[] = {
 		.process_pkt	= usbtouch_process_multi,
 		.get_pkt_len	= egalax_get_pkt_len,
 		.read_data	= egalax_read_data,
+		.init		= egalax_init,
 	},
 #endif
 

-- 
1.7.0.4

On Fri, Aug 31, 2012 at 08:37:26PM -0400, Forest Bond wrote:

	if (!buf)
		return -ENOMEM;

+	buf[0] = EGALAX_PKT_TYPE_DIAG;
+	buf[1] = 1;	/* length */
+	buf[2] = 'A';	/* command - check active */
+
+	for (i = 0; i < 3; i++) {
+		ret = usb_control_msg(udev, usb_sndctrlpipe(udev, 0),
+				      0,
+				      USB_DIR_OUT | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
+				      0, 0, buf, 3,
+				      USB_CTRL_SET_TIMEOUT);
+		if (ret >= 0) {
+			ret = 0;
+			break;
+		}
+		if (ret != -EPIPE)
+			break;
+	}
+
+	kfree(buf);
+
+	return ret;
+}