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: >> >> 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. Yeah that shouldn't be a problem. I'll fix that. > >> 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? > >> 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. > -- 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
