linux-kernel - Re: [PATCH 1/2] gpio: add pin biasing and drive mode to gpiolib

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

Message-ID: <BANLkTimwbsmQw0Dawz_+LpVf+wU60AbB0g@mail.gmail.com>
Date:	Sun, 17 Apr 2011 23:58:16 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	Grant Likely <grant.likely@...retlab.ca>,
	Lee Jones <lee.jones@...aro.org>, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/2] gpio: add pin biasing and drive mode to gpiolib

2011/4/17 Alan Cox <alan@...rguk.ukuu.org.uk>:

>> + * enum gpio_drive - drive modes for GPIOs (output)
>> + * @GPIO_DRIVE_PUSH_PULL: the GPIO will be driven actively high and low, this
>> + *   is the most typical case and is typically achieved with two active
>> + *   transistors on the output
>> + * @GPIO_DRIVE_OPEN_DRAIN: the GPIO will be driven with open drain (open
>> + *   collector) which means it is usually wired with other output ports
>> + *   which are then pulled up with an external resistor
>> + * @GPIO_DRIVE_OPEN_SOURCE: the GPIO will be driven with open drain
>> + *   (open emitter) which is the same as open drain mutatis mutandis but
>> + *   pulled to ground
>
> How about "off". As I've pointed out at various times some devices have
> GPIO pins that may or may not be connected depending upon what other chip
> logic is doing.

Sure, why not.

> As I've also noted with various other previous suggestions for API
> additions you also need an "unknown" state so that a device can implement
> the methods but indicate for some pins the value is unknown due to
> hardware or firmware limitations.

OK do you want an unknown biasing mode too, or is "floating" enough
of a default to cover that?

Yours,
Linus Walleij
--
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/