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SubjectRe: [PATCH v3] ARM: bcm2835: Add names for the Raspberry Pi GPIO lines
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On 10/27/2016 10:52 AM, Eric Anholt wrote:
> From: Linus Walleij <linus.walleij@linaro.org>
>
> The idea is to give useful names to GPIO lines that an implementer
> will be using from userspace, e.g. for maker type projects. These are
> user-visible using tools/gpio/lsgpio.c

> arch/arm/boot/dts/bcm2835-rpi-a-plus.dts | 65 +++++++++++++++++++++++++++++++
> arch/arm/boot/dts/bcm2835-rpi-a.dts | 67 ++++++++++++++++++++++++++++++++
> arch/arm/boot/dts/bcm2835-rpi-b-plus.dts | 66 +++++++++++++++++++++++++++++++
> arch/arm/boot/dts/bcm2835-rpi-b-rev2.dts | 66 +++++++++++++++++++++++++++++++
> arch/arm/boot/dts/bcm2835-rpi-b.dts | 67 ++++++++++++++++++++++++++++++++

Aren't the A and B rev 2 pinouts the same. If so, why duplicate the
content between the files instead of creating an inclue file? Same for
A+, B+, Pi 2, and Pi 3. Shouldn't this patch update the Pi 2 and Pi 3
DTs too?

> diff --git a/arch/arm/boot/dts/bcm2835-rpi-a-plus.dts b/arch/arm/boot/dts/bcm2835-rpi-a-plus.dts

> &gpio {
> + /*
> + * This is based on the unreleased schematic for the Model A+.
> + *
> + * Legend:
> + * "NC" = not connected (no rail from the SoC)
> + * "FOO" = GPIO line named "FOO" on the schematic
> + * "FOO_N" = GPIO line named "FOO" on schematic, active low
> + */
> + gpio-line-names = "SDA0",
> + "SCL0",

> diff --git a/arch/arm/boot/dts/bcm2835-rpi-b-plus.dts b/arch/arm/boot/dts/bcm2835-rpi-b-plus.dts

> &gpio {
> + /*
> + * Taken from Raspberry-Pi-B-Plus-V1.2-Schematics.pdf
> + * RPI-BPLUS sheet 1
> + *
> + * Legend:
> + * "NC" = not connected (no rail from the SoC)
> + * "FOO" = GPIO line named "FOO" on the schematic
> + * "FOO_N" = GPIO line named "FOO" on schematic, active low
> + */
> + gpio-line-names = "ID_SD",
> + "ID_SC",

I think the whole point of naming GPIOs is to give users the same
experience across the different boards where the same semantics exist in
HW. Both the A+ and B+ use GPIO0/1 (a/k/a ID_SD/ID_SC a/k/a SDA0/SCL0)
for the same semantic purpose and are exposed in the same externally
visible way (same pins on the expansion header); the board ID EEPROM.
Therefore I assert the names of these GPIOs should be identical on all
boards that use them for that purpose, to allow SW (or human knowledge)
portability between the boards.

> + "GPIO17",

This pin is known as GPIO_GEN0 on the expansion header. Given the
expansion header is all end-users likely care about, and other pins
(e.g. SPI_CE1_N) are named after the expansion header, shouldn't this
patch use the GPIO expansion header naming for all pins that are routed
to that header?

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