From: Linus Walleij <linus.walleij@linaro.org>
To: Phil Elwell <phil@raspberrypi.org>
Cc: "Phil Reid" <preid@electromag.com.au>,
"Jason Kridner" <jkridner@gmail.com>,
"Jan Kundrát" <jan.kundrat@cesnet.cz>,
"Sebastian Reichel" <sre@kernel.org>,
"Bartosz Golaszewski" <bgolaszewski@baylibre.com>,
"open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>
Subject: Re: Multiple SPI MCP23S17s sharing a CS line
Date: Thu, 28 Nov 2019 13:24:05 +0100 [thread overview]
Message-ID: <CACRpkdZhoms7+gdM742=r+AsVyNPZkb2zcR3-yrTujvBFR0mCg@mail.gmail.com> (raw)
In-Reply-To: <77b3a320-20a3-5993-b7cb-e3d6f171cd56@raspberrypi.org>
On Thu, Nov 28, 2019 at 10:25 AM Phil Elwell <phil@raspberrypi.org> wrote:
> [Me]
> > By introducing such child nodes it gets possible to reference
> > these chips by phandle <&mcp1 ...>;
> >
> > Notice use of reg attribute to address subchip.
>
> I've not spent enough time in this area to know all of the rules and
> conventions, but it strikes me that if you treat the parent as a kind of
> bus and the "reg" properties as being the addresses (rather than
> indexes) then you no longer need the present mask.
Indeed, that would involve deprecating the present mask and
use the reg =<> property to figure out which chips are
connected instead.
Yours,
Linus Walleij
prev parent reply other threads:[~2019-11-28 12:24 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-27 11:20 Multiple SPI MCP23S17s sharing a CS line Phil Elwell
2019-11-27 12:36 ` Linus Walleij
2019-11-28 4:11 ` Phil Reid
2019-11-28 9:17 ` Linus Walleij
2019-11-28 13:44 ` Jan Kundrát
2019-11-28 9:25 ` Phil Elwell
2019-11-28 12:24 ` Linus Walleij [this message]
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