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From: "Andrew Jeffery" <andrew@aj.id.au>
To: "Arnd Bergmann" <arnd@kernel.org>,
	"Dmitry Torokhov" <dmitry.torokhov@gmail.com>
Cc: openipmi-developer@lists.sourceforge.net,
	"OpenBMC Maillist" <openbmc@lists.ozlabs.org>,
	"Corey Minyard" <minyard@acm.org>,
	"Joel Stanley" <joel@jms.id.au>,
	"Ryan Chen" <ryan_chen@aspeedtech.com>,
	DTML <devicetree@vger.kernel.org>,
	"Tomer Maimon" <tmaimon77@gmail.com>,
	linux-aspeed <linux-aspeed@lists.ozlabs.org>,
	"open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>,
	"Avi Fishman" <avifishman70@gmail.com>,
	"Patrick Venture" <venture@google.com>,
	"Linus Walleij" <linus.walleij@linaro.org>,
	"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
	"Tali Perry" <tali.perry1@gmail.com>,
	"Rob Herring" <robh+dt@kernel.org>,
	"Lee Jones" <lee.jones@linaro.org>,
	"Chia-Wei, Wang" <chiawei_wang@aspeedtech.com>,
	"Linux ARM" <linux-arm-kernel@lists.infradead.org>,
	"Benjamin Fair" <benjaminfair@google.com>
Subject: Re: [PATCH v2 16/21] ipmi: kcs_bmc: Add a "raw" character device interface
Date: Mon, 12 Apr 2021 11:03:52 +0930	[thread overview]
Message-ID: <ba63f830-4758-49aa-a63e-f204a8eec1b4@www.fastmail.com> (raw)
In-Reply-To: <CAK8P3a1HDQdbTAT4aRMLu-VFz720ynPqPHG5b22NZ5p5QfUqOw@mail.gmail.com>

On Fri, 9 Apr 2021, at 17:25, Arnd Bergmann wrote:
> On Fri, Mar 19, 2021 at 7:31 AM Andrew Jeffery <andrew@aj.id.au> wrote:
> >
> > The existing IPMI chardev encodes IPMI behaviours as the name suggests.
> > However, KCS devices are useful beyond IPMI (or keyboards), as they
> > provide a means to generate IRQs and exchange arbitrary data between a
> > BMC and its host system.
> 
> I only noticed the series after Joel asked about the DT changes on the arm
> side. One question though:
> 
> How does this related to the drivers/input/serio/ framework that also talks
> to the keyboard controller for things that are not keyboards?

I've taken a brief look and I feel they're somewhat closely related.

It's plausible that we could wrangle the code so the Aspeed and Nuvoton 
KCS drivers move under drivers/input/serio. If you squint, the i8042 
serio device driver has similarities with what the Aspeed and Nuvoton 
device drivers are providing to the KCS IPMI stack.

Both the KCS IPMI and raw chardev I've implemented in this patch need 
both read and write access to the status register (STR). serio could 
potentially expose its value through serio_interrupt() using the 
SERIO_OOB_DATA flag, but I haven't put any thought into it beyond this 
sentence. We'd need some extra support for writing STR via the serio 
API. I'm not sure that fits into the abstraction (unless we make 
serio_write() take a flags argument?).

In that vein, the serio_raw interface is close to the functionality 
that the raw chardev provides in this patch, though again serio_raw 
lacks userspace access to STR. Flags are ignored in the ->interrupt() 
callback so all values received via ->interrupt() are exposed as data. 
The result is there's no way to take care of SERIO_OOB_DATA in the 
read() path. Given that, I think we'd have to expose an ioctl() to 
access the STR value after taking care of SERIO_OOB_DATA in 
->interrupt().

I'm not sure where that lands us.

Dmitry, any thoughts here?

> Are these
> separate communication channels on adjacent I/O ports, or does there
> need to be some arbitration?

As it stands there's no arbitration.

Cheers,

Andrew

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  parent reply	other threads:[~2021-04-12  1:36 UTC|newest]

Thread overview: 67+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-19  6:27 [PATCH v2 01/21] dt-bindings: aspeed-lpc: Remove LPC partitioning Andrew Jeffery
2021-03-19  6:27 ` [PATCH v2 02/21] ARM: dts: Remove LPC BMC and Host partitions Andrew Jeffery
2021-03-19  6:27 ` [PATCH v2 03/21] ipmi: kcs: aspeed: Adapt to new LPC DTS layout Andrew Jeffery
2021-04-09  3:35   ` Joel Stanley
2021-03-19  6:27 ` [PATCH v2 04/21] pinctrl: aspeed-g5: Adapt to new LPC device tree layout Andrew Jeffery
2021-04-09  3:36   ` Joel Stanley
2021-03-19  6:27 ` [PATCH v2 05/21] soc: aspeed: " Andrew Jeffery
2021-04-09  3:38   ` Joel Stanley
2021-03-19  6:27 ` [PATCH v2 06/21] ipmi: kcs_bmc_aspeed: Use of match data to extract KCS properties Andrew Jeffery
2021-04-06  6:07   ` ChiaWei Wang
2021-04-09  3:24   ` Zev Weiss
2021-03-19  6:27 ` [PATCH v2 07/21] ipmi: kcs_bmc: Make status update atomic Andrew Jeffery
2021-04-09  5:32   ` Zev Weiss
2021-03-19  6:27 ` [PATCH v2 08/21] ipmi: kcs_bmc: Rename {read, write}_{status, data}() functions Andrew Jeffery
2021-04-09  5:33   ` Zev Weiss
2021-03-19  6:27 ` [PATCH v2 09/21] ipmi: kcs_bmc: Split out kcs_bmc_cdev_ipmi Andrew Jeffery
2021-04-09  3:56   ` Zev Weiss
2021-04-09  5:48     ` Andrew Jeffery
2021-04-09 19:21       ` Zev Weiss
2021-03-19  6:27 ` [PATCH v2 10/21] ipmi: kcs_bmc: Turn the driver data-structures inside-out Andrew Jeffery
2021-04-09  3:57   ` Zev Weiss
2021-04-09  5:59     ` Andrew Jeffery
2021-04-09  6:25       ` Zev Weiss
2021-04-09 19:26         ` Zev Weiss
2021-04-11 23:00           ` Andrew Jeffery
2021-03-19  6:27 ` [PATCH v2 11/21] ipmi: kcs_bmc: Split headers into device and client Andrew Jeffery
2021-04-09  4:01   ` Zev Weiss
2021-04-09  6:06     ` Andrew Jeffery
2021-03-19  6:27 ` [PATCH v2 12/21] ipmi: kcs_bmc: Strip private client data from struct kcs_bmc Andrew Jeffery
2021-04-09  4:07   ` Zev Weiss
2021-04-09  6:15     ` Andrew Jeffery
2021-03-19  6:27 ` [PATCH v2 13/21] ipmi: kcs_bmc: Decouple the IPMI chardev from the core Andrew Jeffery
2021-04-06  6:07   ` ChiaWei Wang
2021-04-09  4:35   ` Zev Weiss
2021-04-09  6:24     ` Andrew Jeffery
2021-03-19  6:27 ` [PATCH v2 14/21] ipmi: kcs_bmc: Allow clients to control KCS IRQ state Andrew Jeffery
2021-04-09  4:37   ` Zev Weiss
2021-04-09  6:39     ` Andrew Jeffery
2021-03-19  6:27 ` [PATCH v2 15/21] ipmi: kcs_bmc: Don't enforce single-open policy in the kernel Andrew Jeffery
2021-04-09  5:07   ` Zev Weiss
2021-03-19  6:27 ` [PATCH v2 16/21] ipmi: kcs_bmc: Add a "raw" character device interface Andrew Jeffery
2021-04-09  5:17   ` Zev Weiss
2021-04-09  6:46     ` Andrew Jeffery
2021-04-09  7:55   ` Arnd Bergmann
2021-04-09  8:51     ` Andrew Jeffery
2021-04-12  1:33     ` Andrew Jeffery [this message]
2021-04-12  8:48       ` Arnd Bergmann
2021-04-12 23:45         ` Andrew Jeffery
2021-04-13  8:22           ` Arnd Bergmann
2021-04-14  0:30             ` Andrew Jeffery
2021-03-19  6:27 ` [PATCH v2 17/21] dt-bindings: ipmi: Convert ASPEED KCS binding to schema Andrew Jeffery
2021-03-26  1:48   ` Rob Herring
2021-04-09  5:15   ` Zev Weiss
2021-04-09  5:33     ` Andrew Jeffery
2021-04-09  5:44       ` Zev Weiss
2021-04-09  8:46         ` Zev Weiss
2021-03-19  6:27 ` [PATCH v2 18/21] dt-bindings: ipmi: Add optional SerIRQ property to ASPEED KCS devices Andrew Jeffery
2021-03-26  1:49   ` Rob Herring
2021-03-19  6:27 ` [PATCH v2 19/21] ipmi: kcs_bmc_aspeed: Implement KCS SerIRQ configuration Andrew Jeffery
2021-04-01  9:30   ` [EXTERNAL] " Zev Weiss
2021-03-19  6:27 ` [PATCH v2 20/21] ipmi: kcs_bmc_aspeed: Fix IBFIE typo from datasheet Andrew Jeffery
2021-04-09  5:40   ` Zev Weiss
2021-03-19  6:27 ` [PATCH v2 21/21] ipmi: kcs_bmc_aspeed: Optionally apply status address Andrew Jeffery
2021-04-01 18:18   ` Re " Zev Weiss
2021-04-06  6:09   ` ChiaWei Wang
2021-04-09  3:18 ` [PATCH v2 01/21] dt-bindings: aspeed-lpc: Remove LPC partitioning Joel Stanley
2021-04-09  5:24   ` Andrew Jeffery

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