On Wed, Oct 14, 2015 at 08:58:32PM -0500, Franklin S Cooper Jr. wrote: > > > On 10/14/2015 06:39 PM, Dmitry Torokhov wrote: > > On Wed, Oct 07, 2015 at 07:21:38AM -0500, fcooper@xxxxxx wrote: > >> From: Franklin S Cooper Jr <fcooper@xxxxxx> > >> > >> 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 <fcooper@xxxxxx> > >> --- > >> 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. > 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. Can we unify the calculation to be: datalen = tplen * MAX_SUPPORT_POINTS + offset + crc_len; By the way, what version of firmware you tested your changes with? > > 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. > > > > I also wonder why we need extra 1 byte in M06 case. > > > > Lothar? > > > > Thanks. > > > Thanks. -- Dmitry -- 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
