On Wed, Jul 6, 2011 at 1:42 AM, Chase Douglas
[off-list ref] wrote:

On 06/28/2011 10:07 PM, djkurtz@chromium.org wrote:

quoted

From: Daniel Kurtz <redacted>

Synaptics touchpads report increasing y from bottom to top.
This is inverted from normal userspace "top of screen is 0" coordinates.
Thus, the kernel driver reports inverted y coordinates to userspace.

In some cases, however, y = 0 is sent by the touchpad.
In these cases, the kernel driver should not invert, and just report 0.

Under what cases is y sent as 0, and why do we want to report it as 0 to
userspace?

I know of two such cases for the image sensor:
  (1) When all fingers, save the first finger are removed, an AGM
packet with (x=0, y=0, z=0) is sent.
  (2) When all fingers are removed, an SGM packet with (x=0, y=0, z=0) is sent.

After uploading this patch set, I played with the profile sensor
again, and I also saw it sometimes sends y=1 packets.  I don't know
what those are.

This is mostly useful for debugging the kernel driver.
When observing the raw position values, the special 0 (and 1?) cases
are more obvious when not inverted.
I think I am misleading in my commit message.  I don't believe these
are actually ever passed through to userspace.

quoted

This patch also refactors the inversion into a macro, and moves it
into packet processing instead of during position reporting.

It's getting really hard to read the bit transformations with a macro.
I'd prefer an approach that splits the computation. Maybe:

hw->y = bit_manipulations;
hw->y = INVERT_Y(hw->y);

(could use a temporary variable too)

Or maybe define a static inline function that takes the hw state as an arg:

hw->y = bit_manipulations;
fix_y(hw);

I'd prefer this implementation if every scenario involved manipulating
the y value of the hw state struct.

Ok.  This option sounds good to me.  Both the sgm & agm cases
manipulate the same struct.

Also, it would be great if you could add your explanation of why Y is
inverted as a comment above INVERT_Y (or whatever function/macro it
eventually becomes).

Ok.  I agree a comment would help.

Thanks for the review!

-Dan

Thanks!

-- Chase

quoted

Signed-off-by: Daniel Kurtz <redacted>
---
 drivers/input/mouse/synaptics.c |   16 +++++++++-------
 1 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/drivers/input/mouse/synaptics.c b/drivers/input/mouse/synaptics.c
index e06e045..f6d0c04 100644
--- a/drivers/input/mouse/synaptics.c
+++ b/drivers/input/mouse/synaptics.c

@@ -44,6 +44,8 @@

 #define YMIN_NOMINAL 1408
 #define YMAX_NOMINAL 4448

+#define INVERT_Y(y) (((y) != 0) ? (YMAX_NOMINAL + YMIN_NOMINAL - (y)) : 0)
+

 /*****************************************************************************
  *   Stuff we need even when we do not want native Synaptics support

@@ -409,9 +411,9 @@ static int synaptics_parse_hw_state(const unsigned char buf[],

              hw->x = (((buf[3] & 0x10) << 8) |
                       ((buf[1] & 0x0f) << 8) |
                       buf[4]);
-             hw->y = (((buf[3] & 0x20) << 7) |
+             hw->y = INVERT_Y((((buf[3] & 0x20) << 7) |
                       ((buf[1] & 0xf0) << 4) |
-                      buf[5]);
+                      buf[5]));

              hw->z = buf[2];
              hw->w = (((buf[0] & 0x30) >> 2) |

@@ -421,7 +423,8 @@ static int synaptics_parse_hw_state(const unsigned char buf[],

              if (SYN_CAP_ADV_GESTURE(priv->ext_cap_0c) && hw->w == 2) {
                      /* Gesture packet: (x, y, z) at half resolution */
                      priv->mt.x = (((buf[4] & 0x0f) << 8) | buf[1]) << 1;
-                     priv->mt.y = (((buf[4] & 0xf0) << 4) | buf[2]) << 1;
+                     priv->mt.y = INVERT_Y((((buf[4] & 0xf0) << 4)
+                                           | buf[2]) << 1);
                      priv->mt.z = ((buf[3] & 0x30) | (buf[5] & 0x0f)) << 1;
                      return 1;
              }

@@ -473,7 +476,7 @@ static int synaptics_parse_hw_state(const unsigned char buf[],

              }
      } else {
              hw->x = (((buf[1] & 0x1f) << 8) | buf[2]);
-             hw->y = (((buf[4] & 0x1f) << 8) | buf[5]);
+             hw->y = INVERT_Y(((buf[4] & 0x1f) << 8) | buf[5]);

              hw->z = (((buf[0] & 0x30) << 2) | (buf[3] & 0x3F));
              hw->w = (((buf[1] & 0x80) >> 4) | ((buf[0] & 0x04) >> 1));

@@ -491,8 +494,7 @@ static void set_slot(struct input_dev *dev, int slot, bool active, int x, int y)

      input_mt_report_slot_state(dev, MT_TOOL_FINGER, active);
      if (active) {
              input_report_abs(dev, ABS_MT_POSITION_X, x);
-             input_report_abs(dev, ABS_MT_POSITION_Y,
-                              YMAX_NOMINAL + YMIN_NOMINAL - y);
+             input_report_abs(dev, ABS_MT_POSITION_Y, y);
      }
 }

@@ -584,7 +586,7 @@ static void synaptics_process_packet(struct psmouse *psmouse)

      if (num_fingers > 0) {
              input_report_abs(dev, ABS_X, hw.x);
-             input_report_abs(dev, ABS_Y, YMAX_NOMINAL + YMIN_NOMINAL - hw.y);
+             input_report_abs(dev, ABS_Y, hw.y);
      }
      input_report_abs(dev, ABS_PRESSURE, hw.z);

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