[PATCH] Input: usbtouchscreen - separate report and transmit buffer size handling

[PATCH] Input: usbtouchscreen - separate report and transmit buffer size handling

[Christian Engelmayer]

This patch supports the separate handling of the USB transfer buffer length
and the length of the buffer used for multi packet support. The USB transfer
size can now be explicitly configured via the device_info record. Otherwise
it defaults to the configured report packet size as before. For devices
supporting multiple report or diagnostic packets, the USB transfer size is
now reduced to the USB endpoints wMaxPacketSize if not explicitly set.

This fixes an issue where event reporting can be delayed for an arbitrary
time for multi packet devices. For instance the report size for eGalax devices
is defined to the 16 byte maximum diagnostic packet size as opposed to the 5
byte report packet size. In case the driver requests 16 byte from the USB
interrupt endpoint, the USB host controller driver needs to split up the
request into 2 accesses according to the endpoints wMaxPacketSize of 8 byte.
When the first transfer is answered by the eGalax device with not less than
the full 8 byte requested, the host controller has got no way of knowing
whether the touch controller has got additional data queued and will issue
the second transfer. If per example a liftoff event finishes at such a
wMaxPacketSize boundary, the data will not be available to the usbtouch driver
until a further event is triggered and transfered to the host. From user
perspective the BTN_TOUCH release event in this case is stuck until the next
touch down event.

Signed-off-by: Christian Engelmayer <christian.engelmayer@frequentis.com>
---
 drivers/input/touchscreen/usbtouchscreen.c |   16 ++++++++++++----
 1 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/drivers/input/touchscreen/usbtouchscreen.c b/drivers/input/touchscreen/usbtouchscreen.c
index 721fdb3..aa1f6a7 100644
--- a/drivers/input/touchscreen/usbtouchscreen.c
+++ b/drivers/input/touchscreen/usbtouchscreen.c
@@ -76,6 +76,7 @@ struct usbtouch_device_info {
 	int min_yc, max_yc;
 	int min_press, max_press;
 	int rept_size;
+	int xmit_size;
 
 	/*
 	 * Always service the USB devices irq not just when the input device is
@@ -1523,7 +1524,7 @@ static int usbtouch_reset_resume(struct usb_interface *intf)
 static void usbtouch_free_buffers(struct usb_device *udev,
 				  struct usbtouch_usb *usbtouch)
 {
-	usb_free_coherent(udev, usbtouch->type->rept_size,
+	usb_free_coherent(udev, usbtouch->type->xmit_size,
 			  usbtouch->data, usbtouch->data_dma);
 	kfree(usbtouch->buffer);
 }
@@ -1567,8 +1568,15 @@ static int usbtouch_probe(struct usb_interface *intf,
 	usbtouch->type = type;
 	if (!type->process_pkt)
 		type->process_pkt = usbtouch_process_pkt;
+	if (!type->xmit_size) {
+		if ((type->get_pkt_len) &&
+		    (type->rept_size > le16_to_cpu(endpoint->wMaxPacketSize)))
+			type->xmit_size = le16_to_cpu(endpoint->wMaxPacketSize);
+		else
+			type->xmit_size = type->rept_size;
+	}
 
-	usbtouch->data = usb_alloc_coherent(udev, type->rept_size,
+	usbtouch->data = usb_alloc_coherent(udev, type->xmit_size,
 					    GFP_KERNEL, &usbtouch->data_dma);
 	if (!usbtouch->data)
 		goto out_free;
@@ -1628,12 +1636,12 @@ static int usbtouch_probe(struct usb_interface *intf,
 	if (usb_endpoint_type(endpoint) == USB_ENDPOINT_XFER_INT)
 		usb_fill_int_urb(usbtouch->irq, udev,
 			 usb_rcvintpipe(udev, endpoint->bEndpointAddress),
-			 usbtouch->data, type->rept_size,
+			 usbtouch->data, type->xmit_size,
 			 usbtouch_irq, usbtouch, endpoint->bInterval);
 	else
 		usb_fill_bulk_urb(usbtouch->irq, udev,
 			 usb_rcvbulkpipe(udev, endpoint->bEndpointAddress),
-			 usbtouch->data, type->rept_size,
+			 usbtouch->data, type->xmit_size,
 			 usbtouch_irq, usbtouch);
 
 	usbtouch->irq->dev = udev;
-- 
1.7.2.5

Re: [PATCH] Input: usbtouchscreen - separate report and transmit buffer size handling

[Dmitry Torokhov]

Hi Christian,

On Tue, Oct 15, 2013 at 04:50:00PM +0200, Christian Engelmayer wrote:
> This patch supports the separate handling of the USB transfer buffer length
> and the length of the buffer used for multi packet support. The USB transfer
> size can now be explicitly configured via the device_info record. Otherwise
> it defaults to the configured report packet size as before. For devices
> supporting multiple report or diagnostic packets, the USB transfer size is
> now reduced to the USB endpoints wMaxPacketSize if not explicitly set.
> 
> This fixes an issue where event reporting can be delayed for an arbitrary
> time for multi packet devices. For instance the report size for eGalax devices
> is defined to the 16 byte maximum diagnostic packet size as opposed to the 5
> byte report packet size. In case the driver requests 16 byte from the USB
> interrupt endpoint, the USB host controller driver needs to split up the
> request into 2 accesses according to the endpoints wMaxPacketSize of 8 byte.
> When the first transfer is answered by the eGalax device with not less than
> the full 8 byte requested, the host controller has got no way of knowing
> whether the touch controller has got additional data queued and will issue
> the second transfer. If per example a liftoff event finishes at such a
> wMaxPacketSize boundary, the data will not be available to the usbtouch driver
> until a further event is triggered and transfered to the host. From user
> perspective the BTN_TOUCH release event in this case is stuck until the next
> touch down event.
> 
> Signed-off-by: Christian Engelmayer <christian.engelmayer@frequentis.com>
> ---
>  drivers/input/touchscreen/usbtouchscreen.c |   16 ++++++++++++----
>  1 files changed, 12 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/input/touchscreen/usbtouchscreen.c b/drivers/input/touchscreen/usbtouchscreen.c
> index 721fdb3..aa1f6a7 100644
> --- a/drivers/input/touchscreen/usbtouchscreen.c
> +++ b/drivers/input/touchscreen/usbtouchscreen.c
> @@ -76,6 +76,7 @@ struct usbtouch_device_info {
>  	int min_yc, max_yc;
>  	int min_press, max_press;
>  	int rept_size;
> +	int xmit_size;
>  
>  	/*
>  	 * Always service the USB devices irq not just when the input device is
> @@ -1523,7 +1524,7 @@ static int usbtouch_reset_resume(struct usb_interface *intf)
>  static void usbtouch_free_buffers(struct usb_device *udev,
>  				  struct usbtouch_usb *usbtouch)
>  {
> -	usb_free_coherent(udev, usbtouch->type->rept_size,
> +	usb_free_coherent(udev, usbtouch->type->xmit_size,
>  			  usbtouch->data, usbtouch->data_dma);
>  	kfree(usbtouch->buffer);
>  }
> @@ -1567,8 +1568,15 @@ static int usbtouch_probe(struct usb_interface *intf,
>  	usbtouch->type = type;
>  	if (!type->process_pkt)
>  		type->process_pkt = usbtouch_process_pkt;
> +	if (!type->xmit_size) {
> +		if ((type->get_pkt_len) &&
> +		    (type->rept_size > le16_to_cpu(endpoint->wMaxPacketSize)))
> +			type->xmit_size = le16_to_cpu(endpoint->wMaxPacketSize);
> +		else
> +			type->xmit_size = type->rept_size;

'type' points to a shared data structure and should not be modified. It
looks like we already violating this so a cleanup patch would be
appreciated as well.

BTW, maybe we should do:

	u16 wMaxPaxetSize = le16_to_cpu(endpoint->wMaxPacketSize);
	xmit_size = min(type->rept_size, wMaxPaxetSize);

?

Thanks.

-- 
Dmitry

[PATCH v2] Input: usbtouchscreen - separate report and transmit buffer size handling

[Christian Engelmayer]

This patch supports the separate handling of the USB transfer buffer length
and the length of the buffer used for multi packet support. For devices
supporting multiple report or diagnostic packets, the USB transfer size is now
limited to the USB endpoints wMaxPacketSize - otherwise it defaults to the
configured report packet size as before

This fixes an issue where event reporting can be delayed for an arbitrary
time for multi packet devices. For instance the report size for eGalax devices
is defined to the 16 byte maximum diagnostic packet size as opposed to the 5
byte report packet size. In case the driver requests 16 byte from the USB
interrupt endpoint, the USB host controller driver needs to split up the
request into 2 accesses according to the endpoints wMaxPacketSize of 8 byte.
When the first transfer is answered by the eGalax device with not less than
the full 8 byte requested, the host controller has got no way of knowing
whether the touch controller has got additional data queued and will issue
the second transfer. If per example a liftoff event finishes at such a
wMaxPacketSize boundary, the data will not be available to the usbtouch driver
until a further event is triggered and transfered to the host. From user
perspective the BTN_TOUCH release event in this case is stuck until the next
touch down event.

Signed-off-by: Christian Engelmayer <christian.engelmayer-USXAA5bZaHGDvotElmWtJA@public.gmane.org>
---
v2: Added changes suggested by Dmitry Torokhov:

    * Prefer a temporary variable over a multiple conversion of wMaxPaxetSize.
    * Avoid further modifiction of the shared device info structure.

The existing violation in the probe function

	if (!type->process_pkt)
		type->process_pkt = usbtouch_process_pkt;

seems to be conveniance triggered and while at least at the moment applicable
for all devices of a type, could be easily removed. For a complete cleanup and
eg. setting the shared device information 'const', we would have to adapt the
Nexio support first - nexio_read_data:

	if (!usbtouch->type->max_xc) {
		usbtouch->type->max_xc = 2 * x_len;
		input_set_abs_params(usbtouch->input, ABS_X,
				     0, usbtouch->type->max_xc, 0, 0);
		usbtouch->type->max_yc = 2 * y_len;
		input_set_abs_params(usbtouch->input, ABS_Y,
				     0, usbtouch->type->max_yc, 0, 0);
	}
---
 drivers/input/touchscreen/usbtouchscreen.c |   13 +++++++++----
 1 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/input/touchscreen/usbtouchscreen.c b/drivers/input/touchscreen/usbtouchscreen.c
index 721fdb3..d632848 100644
--- a/drivers/input/touchscreen/usbtouchscreen.c
+++ b/drivers/input/touchscreen/usbtouchscreen.c
@@ -106,6 +106,7 @@ struct usbtouch_device_info {
 struct usbtouch_usb {
 	unsigned char *data;
 	dma_addr_t data_dma;
+	int data_size;
 	unsigned char *buffer;
 	int buf_len;
 	struct urb *irq;
@@ -1523,7 +1524,7 @@ static int usbtouch_reset_resume(struct usb_interface *intf)
 static void usbtouch_free_buffers(struct usb_device *udev,
 				  struct usbtouch_usb *usbtouch)
 {
-	usb_free_coherent(udev, usbtouch->type->rept_size,
+	usb_free_coherent(udev, usbtouch->data_size,
 			  usbtouch->data, usbtouch->data_dma);
 	kfree(usbtouch->buffer);
 }
@@ -1548,6 +1549,7 @@ static int usbtouch_probe(struct usb_interface *intf,
 	struct usb_endpoint_descriptor *endpoint;
 	struct usb_device *udev = interface_to_usbdev(intf);
 	struct usbtouch_device_info *type;
+	int wMaxPacketSize;
 	int err = -ENOMEM;
 
 	/* some devices are ignored */
@@ -1557,6 +1559,7 @@ static int usbtouch_probe(struct usb_interface *intf,
 	endpoint = usbtouch_get_input_endpoint(intf->cur_altsetting);
 	if (!endpoint)
 		return -ENXIO;
+	wMaxPacketSize = le16_to_cpu(endpoint->wMaxPacketSize);
 
 	usbtouch = kzalloc(sizeof(struct usbtouch_usb), GFP_KERNEL);
 	input_dev = input_allocate_device();
@@ -1568,7 +1571,9 @@ static int usbtouch_probe(struct usb_interface *intf,
 	if (!type->process_pkt)
 		type->process_pkt = usbtouch_process_pkt;
 
-	usbtouch->data = usb_alloc_coherent(udev, type->rept_size,
+	usbtouch->data_size = (type->get_pkt_len) ?
+			min(type->rept_size, wMaxPacketSize) : type->rept_size;
+	usbtouch->data = usb_alloc_coherent(udev, usbtouch->data_size,
 					    GFP_KERNEL, &usbtouch->data_dma);
 	if (!usbtouch->data)
 		goto out_free;
@@ -1628,12 +1633,12 @@ static int usbtouch_probe(struct usb_interface *intf,
 	if (usb_endpoint_type(endpoint) == USB_ENDPOINT_XFER_INT)
 		usb_fill_int_urb(usbtouch->irq, udev,
 			 usb_rcvintpipe(udev, endpoint->bEndpointAddress),
-			 usbtouch->data, type->rept_size,
+			 usbtouch->data, usbtouch->data_size,
 			 usbtouch_irq, usbtouch, endpoint->bInterval);
 	else
 		usb_fill_bulk_urb(usbtouch->irq, udev,
 			 usb_rcvbulkpipe(udev, endpoint->bEndpointAddress),
-			 usbtouch->data, type->rept_size,
+			 usbtouch->data, usbtouch->data_size,
 			 usbtouch_irq, usbtouch);
 
 	usbtouch->irq->dev = udev;
-- 
1.7.2.5
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