From: Linus Walleij <linus.walleij-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
To: Rick Altherr <raltherr-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
Cc: "Oleksandr Shamray"
<oleksandrs-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>,
"devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
<devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
"Jiří Pírko" <jiri-rHqAuBHg3fBzbRFIqnYvSA@public.gmane.org>,
"Arnd Bergmann" <arnd-r2nGTMty4D4@public.gmane.org>,
system-sw-low-level-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org,
"Greg KH"
<gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org>,
"OpenBMC Maillist"
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"linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
<linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
openocd-devel-owner-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org,
mec-WqBc5aa1uDFeoWH0uzbU5w@public.gmane.org,
"Rob Herring" <robh+dt-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
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<linux-serial-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
vadimp-45czdsxZ+A5DPfheJLI6IQ@public.gmane.org,
"Tobias Klauser"
<tklauser-93Khv+1bN0NyDzI6CaY1VQ@public.gmane.org>,
"linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
<linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
"linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org"
<linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org>
Subject: Re: [patch v6 0/3] JTAG driver introduction
Date: Mon, 28 Aug 2017 00:30:05 +0200 [thread overview]
Message-ID: <CACRpkdb75L5BrYN+V-BMwzrRm8_Wtymr3d08eMWt43FiBpH5Qg@mail.gmail.com> (raw)
In-Reply-To: <CAPLgG=mv1p98e4Vzso1N-VU=1MSotkTmnF+DcDTXPcd3q-n8HA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
On Fri, Aug 25, 2017 at 6:52 PM, Rick Altherr <raltherr-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org> wrote:
>> Incidentally, people are sending patches to expose the FTDI
>> expanders as common GPIO chips under Linux, so we can
>> internally in the kernel or from the usersapce character device
>> access them as "some GPIOs".
>
> I know my team at Google has an internal patch for exactly that. FTDI
> expanders are complicated as they can be used as UART, GPIO, I2C, SPI
> depending on configuration. Our project was using a mix of I2C and
> GPIO so I directly my team to approach it as an MFD. I'd like to see
> all of these use cases handled by the kernel but I understand the
> other viewpoint of relying on libusb for cross-platform compatiblity.
Hm. I see. But I see people pushing the in-kernel method so I think
it will eventually win out.
>>>> In my worst nightmare they export GPIO lines using
>>>> the horrid ABI in /sys/gpio/*
>>>
>>> https://sourceforge.net/p/openocd/code/ci/v0.10.0/tree/src/jtag/drivers/sysfsgpio.c
>>
>> Gnah!
>> Whoever writes a slot-in replacement making the character device
>> take precendence wins lots of karma.
>
> If they show up at Linux Plumbers or visit San Jose, I'll take them to
> dinner. I didn't see any docs for the chardev in Documentation. I
> _think_ I understand how it works from reading the relevant sections
> of gpiolib.c but I can see how users end up using sysfs instead.
I intended tools/gpio/* to be the documentation:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/tools/gpio
If we need more written documentation we can do it I guess,
Yours,
Linus Walleij
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next prev parent reply other threads:[~2017-08-27 22:30 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-22 16:10 [patch v6 0/3] JTAG driver introduction Oleksandr Shamray
2017-08-22 16:10 ` [patch v6 2/3] drivers: jtag: Add Aspeed SoC 24xx and 25xx families JTAG master driver Oleksandr Shamray
2017-08-22 16:10 ` [patch v6 3/3] Doccumentation: jtag: Add bindings for " Oleksandr Shamray
2017-08-28 8:36 ` Tobias Klauser
[not found] ` <1503418256-5215-1-git-send-email-oleksandrs-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
2017-08-22 16:10 ` [patch v6 1/3] drivers: jtag: Add JTAG core driver Oleksandr Shamray
2017-08-24 21:07 ` [patch v6 0/3] JTAG driver introduction Linus Walleij
[not found] ` <CACRpkdZePXyo8Q36mBH7OnJU3E=yWPWSGkGUOH=zJFMjM=Yrhw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-08-24 21:37 ` Rick Altherr
2017-08-25 8:32 ` Linus Walleij
2017-08-25 8:50 ` Stuart Longland
[not found] ` <593cd0d3-8e06-0992-c155-1322014c0477-3e+Fe6x+DsgJbe36r25VNhCuuivNXqWP@public.gmane.org>
2017-08-25 16:53 ` Rick Altherr
2017-08-27 22:25 ` Linus Walleij
[not found] ` <CACRpkdbozWaL0RXyZXjzxYK3JHiqYziSkTGSgGORdptX-rwR8A-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-08-25 16:52 ` Rick Altherr
[not found] ` <CAPLgG=mv1p98e4Vzso1N-VU=1MSotkTmnF+DcDTXPcd3q-n8HA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-08-27 22:30 ` Linus Walleij [this message]
[not found] ` <CACRpkdb75L5BrYN+V-BMwzrRm8_Wtymr3d08eMWt43FiBpH5Qg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-08-28 2:55 ` Rick Altherr
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