Messages in this thread | | | Date | Wed, 24 Aug 2022 10:39:19 +0200 | Subject | Re: [RESEND PATCH v6 2/3] leds: Add driver for the TLC5925 LED controller | From | Jean-Jacques Hiblot <> |
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On 04/08/2022 23:04, Pavel Machek wrote: > On Thu 2022-08-04 22:23:00, Jean-Jacques Hiblot wrote: >> On 31/07/2022 21:28, Andy Shevchenko wrote: >>> On Fri, Jul 22, 2022 at 10:14 AM Jean-Jacques Hiblot >>> <jjhiblot@traphandler.com> wrote: >>>> The TLC5925 is a 16-channels constant-current LED sink driver. >>>> It is controlled via SPI but doesn't offer a register-based interface. >>>> Instead it contains a shift register and latches that convert the >>>> serial input into a parallel output. >>>> >>>> Datasheet: https://www.ti.com/lit/ds/symlink/tlc5925.pdf >>>> Signed-off-by: Jean-Jacques Hiblot <jjhiblot@traphandler.com> >>>> Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com> >>> Sorry for my slowpokeness, but I just realized that this driver may >>> not be needed. What is the difference to existing gpio-74x164? >> It might work. However it might not be as practical and efficient as the >> dedicated LED driver. >> >> I'll give a try. > It is certainly preffered solution. If you decide to re-submit the > driver anyway, please mention that we already have GPIO driver for > compatible chip, and explain why this is superior.
Hi all,
sorry for the delay. I tried with the 74x164 gpio driver and it works as expected.
The only drawbacks are:
- as-is the 74x164 gpio driver supports only one output-enable gpio. However in practice I don't think multiple OE GPIOs will ever be used.
- with this approach, every time a LED status is changed the whole register has to be sent on the SPI bus. In other words, changes cannot be coalesced.
I don't know if this is enough to make a dedicated TLC5925 driver desirable in the kernel.
JJ
> > Thanks, > Pavel >
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