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SubjectRe: [PATCH 05/15] Input - wacom: compute the HID report size to get the actual packet size
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On Mon, Jun 30, 2014 at 2:26 PM, Benjamin Tissoires
<benjamin.tissoires@redhat.com> wrote:
> This removes an USB dependency and is more accurate: the computed pktlen
> is the actual maximum size of the reports forwarded by the device.
>
> Given that the pktlen is correctly computed/validated, we can store it now
> in the features struct instead of having a special handling in the rest of
> the code.
>
> Likewise, this information is not mandatory anymore in the description
> of devices in wacom_wac.c. They will be removed in a separate patch.
>
> Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>

I'm concerned this new function could be fooled if we release a tablet
that has one report which is longer than the desired report, but none
of the hardware I tested was like this and it would be fairly easy to
address even if it did happen. Thought I should mention it though.

Jason
---
Now instead of four in the eights place /
you’ve got three, ‘Cause you added one /
(That is to say, eight) to the two, /
But you can’t take seven from three, /
So you look at the sixty-fours....


> ---
> drivers/input/tablet/wacom_sys.c | 58 ++++++++++++++++++----------------------
> 1 file changed, 26 insertions(+), 32 deletions(-)
>
> diff --git a/drivers/input/tablet/wacom_sys.c b/drivers/input/tablet/wacom_sys.c
> index cd3d936..3f1cee6 100644
> --- a/drivers/input/tablet/wacom_sys.c
> +++ b/drivers/input/tablet/wacom_sys.c
> @@ -149,7 +149,6 @@ static int wacom_parse_logical_collection(unsigned char *report,
> if (features->type == BAMBOO_PT) {
>
> /* Logical collection is only used by 3rd gen Bamboo Touch */
> - features->pktlen = WACOM_PKGLEN_BBTOUCH3;
> features->device_type = BTN_TOOL_FINGER;
>
> features->x_max = features->y_max =
> @@ -240,29 +239,6 @@ static int wacom_parse_hid(struct hid_device *hdev,
> features->device_type = BTN_TOOL_FINGER;
> /* touch device at least supports one touch point */
> touch_max = 1;
> - switch (features->type) {
> - case TABLETPC2FG:
> - features->pktlen = WACOM_PKGLEN_TPC2FG;
> - break;
> -
> - case MTSCREEN:
> - case WACOM_24HDT:
> - features->pktlen = WACOM_PKGLEN_MTOUCH;
> - break;
> -
> - case MTTPC:
> - case MTTPC_B:
> - features->pktlen = WACOM_PKGLEN_MTTPC;
> - break;
> -
> - case BAMBOO_PT:
> - features->pktlen = WACOM_PKGLEN_BBTOUCH;
> - break;
> -
> - default:
> - features->pktlen = WACOM_PKGLEN_GRAPHIRE;
> - break;
> - }
>
> switch (features->type) {
> case BAMBOO_PT:
> @@ -305,8 +281,6 @@ static int wacom_parse_hid(struct hid_device *hdev,
> }
> } else if (pen) {
> /* penabled only accepts exact bytes of data */
> - if (features->type >= TABLETPC)
> - features->pktlen = WACOM_PKGLEN_GRAPHIRE;
> features->device_type = BTN_TOOL_PEN;
> features->x_max =
> get_unaligned_le16(&report[i + 3]);
> @@ -1227,12 +1201,34 @@ static void wacom_calculate_res(struct wacom_features *features)
> features->unitExpo);
> }
>
> +static int wacom_hid_report_len(struct hid_report *report)
> +{
> + /* equivalent to DIV_ROUND_UP(report->size, 8) + !!(report->id > 0) */
> + return ((report->size - 1) >> 3) + 1 + (report->id > 0);
> +}
> +
> +static size_t wacom_compute_pktlen(struct hid_device *hdev)
> +{
> + struct hid_report_enum *report_enum;
> + struct hid_report *report;
> + size_t size = 0;
> +
> + report_enum = hdev->report_enum + HID_INPUT_REPORT;
> +
> + list_for_each_entry(report, &report_enum->report_list, list) {
> + size_t report_size = wacom_hid_report_len(report);
> + if (report_size > size)
> + size = report_size;
> + }
> +
> + return size;
> +}
> +
> static int wacom_probe(struct hid_device *hdev,
> const struct hid_device_id *id)
> {
> struct usb_interface *intf = to_usb_interface(hdev->dev.parent);
> struct usb_device *dev = interface_to_usbdev(intf);
> - struct usb_endpoint_descriptor *endpoint;
> struct wacom *wacom;
> struct wacom_wac *wacom_wac;
> struct wacom_features *features;
> @@ -1258,6 +1254,7 @@ static int wacom_probe(struct hid_device *hdev,
> wacom_wac = &wacom->wacom_wac;
> wacom_wac->features = *((struct wacom_features *)id->driver_data);
> features = &wacom_wac->features;
> + features->pktlen = wacom_compute_pktlen(hdev);
> if (features->pktlen > WACOM_PKGLEN_MAX) {
> error = -EINVAL;
> goto fail1;
> @@ -1275,8 +1272,6 @@ static int wacom_probe(struct hid_device *hdev,
> usb_make_path(dev, wacom->phys, sizeof(wacom->phys));
> strlcat(wacom->phys, "/input0", sizeof(wacom->phys));
>
> - endpoint = &intf->cur_altsetting->endpoint[0].desc;
> -
> /* set the default size in case we do not get them from hid */
> wacom_set_default_phy(features);
>
> @@ -1287,13 +1282,12 @@ static int wacom_probe(struct hid_device *hdev,
>
> /*
> * Intuos5 has no useful data about its touch interface in its
> - * HID descriptor. If this is the touch interface (wMaxPacketSize
> + * HID descriptor. If this is the touch interface (PacketSize
> * of WACOM_PKGLEN_BBTOUCH3), override the table values.
> */
> if (features->type >= INTUOS5S && features->type <= INTUOSHT) {
> - if (endpoint->wMaxPacketSize == WACOM_PKGLEN_BBTOUCH3) {
> + if (features->pktlen == WACOM_PKGLEN_BBTOUCH3) {
> features->device_type = BTN_TOOL_FINGER;
> - features->pktlen = WACOM_PKGLEN_BBTOUCH3;
>
> features->x_max = 4096;
> features->y_max = 4096;
> --
> 2.0.0
>
--
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