linux-kernel - DT GPIO numbering?

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <20120801152240.GA16388@sig21.net>
Date:	Wed, 1 Aug 2012 17:22:40 +0200
From:	Johannes Stezenbach <js@...21.net>
To:	devicetree-discuss@...ts.ozlabs.org
Cc:	linux-kernel@...r.kernel.org,
	Grant Likely <grant.likely@...retlab.ca>,
	Linus Walleij <linus.walleij@...aro.org>
Subject: DT GPIO numbering?

Hi,

I'm currently learning how Linux devicetree support works,
here is one question I couldn't find an answer for.

I understand that within the devicetree GPIOs are referenced by phandle,
thus the numbers are irrelevant.  However, in sysfs the number is
what is used to access the GPIO, e.g. for debugging or
blinkenlight apps.  How does this fit together?

In the old days platform data was used, e.g.

	struct pl061_platform_data {
		/* number of the first GPIO */
		unsigned	gpio_base;
		...
	};

Now, when DT is used gpio-pl061.c sets gc.base = -1 (dynamic numbering).

Should there be a DT property to assign the number base?

Or is there some better way, e.g. in gpio-mxs.c the code derives
the gc.base from of_alias_get_id(np, "gpio").
Should gpio-pl061.c do the same?

And how about assigning gpio names?  When a name is assigned to
the GPIO, is shows up in sysfs instead of gpio%d, however the
number is still needed for /sys/class/gpio/export, right?

Thanks,
Johannes
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/