On Feb 23 2015 or thereabouts, Mika Westerberg wrote: > Wacom digitizer (WCOM0008) on Lenovo Thinkpad 10 seems to allow reading of > subsequent reports (or part of them) if we read more than wMaxInputLength > of data at the time. This data is not always aligned so that the next > report would start right after another. > > For example we might get following sequence: > > i2c_hid i2c-WCOM0008:00: input: 0a 00 02 21 20 17 ad 22 11 03 > i2c_hid i2c-WCOM0008:00: input: ad 22 11 03 0a 00 02 21 20 17 > ad 22 11 03 0a 00 02 21 20 17 > ad 22 11 03 0a 00 02 21 20 17 > ad 22 11 03 0a 00 02 21 20 17 > ad 22 11 03 0a 00 02 21 20 17 > ad 22 11 03 0a 00 02 21 20 17 > ad 22 11 03 > i2c_hid i2c-WCOM0008:00: input: 02 21 20 17 ad 22 11 03 0a 00 > 02 21 20 17 ad 22 11 03 0a 00 > 02 21 20 17 ad 22 11 03 0a 00 > 02 21 20 17 ad 22 11 03 0a 00 > 02 21 20 17 ad 22 11 03 0a 00 > 02 21 20 17 ad 22 11 03 0a 00 > 02 21 20 17 > i2c_hid i2c-WCOM0008:00: i2c_hid_get_input: incomplete report (76/8450) > > The bufsize is 76 and wMaxInputLength is 10. In above example the first > read gets right amount of data. The second and third reads get full bufsize > (76 bytes) but the report is missing a start already. This causes the > driver to reject the report because we got less than was expected by the > report length (0x2102 = 8450). > > If we read only wMaxInputLength at the time this does not happen at all and > the digitizer works fine. > > Based on this change the driver to read wMaxInputLength bytes instead of > bufsize if the value looks sane. > > Reported-by: Sébastien Bourdeauducq <sb@xxxxxxxxx> > Signed-off-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx> > --- We can actually drop this one. Jiri already applied a patch sent last week which does the exact same thing: https://patchwork.kernel.org/patch/5857521/ (should appear shortly in Jiri's tree I guess). But thanks for confirming that it was really needed for other devices. Cheers, Benjamin > drivers/hid/i2c-hid/i2c-hid.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/drivers/hid/i2c-hid/i2c-hid.c b/drivers/hid/i2c-hid/i2c-hid.c > index 8f1dfc5c5d9c..404ccde49acd 100644 > --- a/drivers/hid/i2c-hid/i2c-hid.c > +++ b/drivers/hid/i2c-hid/i2c-hid.c > @@ -369,9 +369,17 @@ static int i2c_hid_hwreset(struct i2c_client *client) > > static void i2c_hid_get_input(struct i2c_hid *ihid) > { > + unsigned max_input_length = le16_to_cpu(ihid->hdesc.wMaxInputLength); > int ret, ret_size; > int size = ihid->bufsize; > > + /* > + * Take the input length from HID descriptor if it is available and > + * looks reasonable. > + */ > + if (max_input_length > 0) > + size = min_t(unsigned, ihid->bufsize, max_input_length); > + > ret = i2c_master_recv(ihid->client, ihid->inbuf, size); > if (ret != size) { > if (ret < 0) > -- > 2.1.4 > -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
