On 8 December 2014 at 16:03, Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> wrote: > Hi Rafał, > > On Mon, Dec 8, 2014 at 3:47 PM, Rafał Miłecki <zajec5@xxxxxxxxx> wrote: >> On 8 December 2014 at 15:41, Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> wrote: >>> On Mon, Dec 8, 2014 at 3:27 PM, Rafał Miłecki <zajec5@xxxxxxxxx> wrote: >>>> SN54HC595 and SN74HC595 are devices based on shift registers controlled >>>> with 5 input signals (serial-in) and providing 8 outputs (parallel-out). >>>> >>>> They are present on some Broadcom home router boards where manufacturer >>>> needed few extra GPIOs. >>>> >>>> This driver simply uses specified GPIOs to control shift registers and >>>> registers another GPIO chip. So you can call it a GPIO extender. >>>> >>>> Due to the hardware design only output direction is supported. Reading >>>> values is handled using tiny internal cache. >>>> >>>> Signed-off-by: Rafał Miłecki <zajec5@xxxxxxxxx> >>>> --- >>>> .../devicetree/bindings/gpio/gpio-sn54hc595.txt | 35 ++++ >>>> drivers/gpio/Kconfig | 11 ++ >>>> drivers/gpio/Makefile | 1 + >>>> drivers/gpio/gpio-sn54hc595.c | 219 +++++++++++++++++++++ >>> >>> The '595 is already handled by drivers/gpio/gpio-74x164.c. >> >> gpio-74x164.c seems to be tight closely to the SPI. In my case it's >> GPIO-controller '595. > > Right. gpio-74x164.c uses the SPI framework, so it will work with any SPI > master controller, while your driver contains a very simple variant (without any > timing constraints) of spi-gpio.c, and is limited to connecting to GPIO pins. > >> Do you have any other idea how we could handle this? > > Your driver does provide OE support, which gpio-74x164 doesn't support. > Perhaps that can be added to gpio-74x164 instead? It's not the missing OE support in gpio-74x164 that worries me, but the whole rest. I would need to modify gpio-74x164 to: 1) Use another OF table with different entry 2) Use different probe function that doesn't take spi_device parameter and doesn't do spi setup 3) Extend struct gen_74x164_chip to include GPIOs 4) Use totally different __gen_74x164_write_config Amount of shared code would be so small I doubt it's worth it. Both driver are quite trivial (200 or less LOC). Sharing: 1) ~5 lines long __gen_74x164_write_config 2) ~5 lines long gen_74x164_set_value 3) 1 line long gen_74x164_direction_output makes me feel it's not really worth combining these two drivers into a one. -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
