On 10/15/2015 07:16 PM, Dmitry Torokhov wrote:

On Wed, Oct 14, 2015 at 08:58:32PM -0500, Franklin S Cooper Jr. wrote:

quoted

On 10/14/2015 06:39 PM, Dmitry Torokhov wrote:

quoted

On Wed, Oct 07, 2015 at 07:21:38AM -0500, fcooper@ti.com wrote:

quoted

From: Franklin S Cooper Jr <redacted>

Calculate the amount of data that needs to be read for the specified max
number of support points. If the maximum number of support points changes
then the amount that is read from the touch screen controller should
reflect this.

Signed-off-by: Franklin S Cooper Jr <redacted>
---
 drivers/input/touchscreen/edt-ft5x06.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/input/touchscreen/edt-ft5x06.c b/drivers/input/touchscreen/edt-ft5x06.c
index 7239c31..1e0ed6e 100644
--- a/drivers/input/touchscreen/edt-ft5x06.c
+++ b/drivers/input/touchscreen/edt-ft5x06.c

@@ -178,14 +178,16 @@ static irqreturn_t edt_ft5x06_ts_isr(int irq, void *dev_id)
 		cmd = 0xf9; /* tell the controller to send touch data */
 		offset = 5; /* where the actual touch data starts */
 		tplen = 4;  /* data comes in so called frames */
-		datalen = 26; /* how much bytes to listen for */
+
+		/* how many bytes to listen for */
+		datalen = tplen * MAX_SUPPORT_POINTS + offset + 1;
 		break;
 
 	case M09:
 		cmd = 0x02;
 		offset = 1;
 		tplen = 6;
-		datalen = 29;
+		datalen = tplen * MAX_SUPPORT_POINTS - cmd + 1;
 		break;

Hmm, why would formulae for datalen be different depending on the
firmware? And I think original 29 it too low: we need 30 bytes for 5
contacts + 1 to account for offset.

So based on the current ISR we don't care about the touch weight and
which are the last two registers for each touch point. So for the last
touchpoint we really don't need to read the extra two registers (-2).

This is really not obvious. I do not think we'd see any performance
degradation if we actually read the whole last touchpoint.

Yeah that shouldn't be a problem. I'll fix that.

quoted

We need +1 simply for the fact that we read the register at location
cmd.

I am not sure I follow this. We do not reference anything past
rdbuf[(MAX_SUPPORT_POINTS - 1) * tplen + offset] and
our offset takes care of the start position, so why exactly we need the
+1? Ah, CRC is in the extra byte.

Sorry your right the +1 isn't needed.

Can we unify the calculation to be:

	datalen = tplen * MAX_SUPPORT_POINTS + offset + crc_len;

Why do we need the crc_len? M06 is the only one that uses the CRC
and the offset insures we are reading the necessary crc registers.

Unless I'm missing something it would simply be:

datalen = tplen * MAX_SUPPORT_POINTS + offset

By the way, what version of firmware you tested your changes with?

quoted

So 6 * 5 - 2 + 1 which is how we get to 29. The formula looks slightly
different because the registers we are reading are very close to zero
so the math works out to equal the equation I used for M09.

M06 since tplen = 4 then all four registers are used in the ISR per touch
point. Plus the offset and plus 1 again to account for the fact we are reading
the cmd register. But once again it would be nice if someone can confirm this.

quoted

I also wonder why we need extra 1 byte in M06 case.

Lothar?

Thanks.

Thanks.