On Monday 08 December 2014 17:31:45 Rafał Miłecki wrote: > On 8 December 2014 at 16:41, Arnd Bergmann <arnd@xxxxxxxx> wrote: > > On Monday 08 December 2014 16:23:01 Rafał Miłecki wrote: > >> On 8 December 2014 at 16:03, Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> wrote: > >> >> 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 > > > > I think the suggestion was to use the spi-gpio driver in combination > > with gpio-74x164. > > Oh, OK, I've obviously missed that. > > I don't know... I'm somehow not really convinced to that, because > AFAIK there isn't any SPI master device between GPIOs and 'HC595. I > don't know if pretending there is some extra hardware (just to use > another Linux driver/layer) is a good idea. This would: > 1) Not match hardware design > 2) Involve some extra code. > > I'm not even sure if this would work out-of-the box (without some > extra changes) at all. From early look at spi-gpio.c I can't see it > implementing everything I need for GPIO-connected 'HC595. > I think that implementing support for this extra SPI layer will > actually require more code/tricks than a separated driver. The purpose of the spi-gpio driver is to avoid having to write two drivers for every spi slave device if someone wants to drive it using bit-banged gpios. The existing users of the driver are in fact all using spi-gpio, see: arch/arm/boot/dts/armada-xp-lenovo-ix4-300d.dts arch/arm/boot/dts/imx28-cfa10049.dts and in openwrt: target/linux/brcm63xx/patches-3.14/501-board-NB4.patch target/linux/brcm63xx/patches-3.14/526-board_CT6373-1.patch so there shouldn't be too much missing, and extending spi-gpio for any missing features would help other people trying to attach random spi devices using gpio as well. Arnd -- 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
