From: "Andrew Jeffery" <andrew@aj.id.au>
To: "Arnd Bergmann" <arnd@kernel.org>
Cc: Linux ARM <linux-arm-kernel@lists.infradead.org>,
DTML <devicetree@vger.kernel.org>,
"Chia-Wei, Wang" <chiawei_wang@aspeedtech.com>,
Ryan Chen <ryan_chen@aspeedtech.com>,
Tomer Maimon <tmaimon77@gmail.com>,
Corey Minyard <minyard@acm.org>,
Avi Fishman <avifishman70@gmail.com>,
Patrick Venture <venture@google.com>,
OpenBMC Maillist <openbmc@lists.ozlabs.org>,
Dmitry Torokhov <dmitry.torokhov@gmail.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Tali Perry <tali.perry1@gmail.com>,
"open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>,
Rob Herring <robh+dt@kernel.org>,
openipmi-developer@lists.sourceforge.net,
Lee Jones <lee.jones@linaro.org>,
Linus Walleij <linus.walleij@linaro.org>,
linux-aspeed <linux-aspeed@lists.ozlabs.org>,
Benjamin Fair <benjaminfair@google.com>
Subject: Re: [PATCH v2 16/21] ipmi: kcs_bmc: Add a "raw" character device interface
Date: Tue, 13 Apr 2021 09:15:55 +0930 [thread overview]
Message-ID: <e2d7268b-bdaf-45bf-bb21-a5b9f7e985a4@www.fastmail.com> (raw)
In-Reply-To: <CAK8P3a3RXr5CR7DJgD9rEkN8owpPxXRgzRnPB_5LuQcHkzc4LA@mail.gmail.com>
On Mon, 12 Apr 2021, at 18:18, Arnd Bergmann wrote:
> On Mon, Apr 12, 2021 at 3:33 AM Andrew Jeffery <andrew@aj.id.au> wrote:
> > 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.
>
> After looking some more into it, I finally understood that the two are
> rather complementary. While the drivers/char/ipmi/kcs_bmc.c
> is the other (bmc) end of drivers/char/ipmi/ipmi_kcs_sm.c, it seems
> that the proposed kcs_bmc_cdev_raw.c interface would be
> what corresponds to the other side of
> drivers/input/serio/i8042.c+userio.c.
Right. I guess the question is should we be splitting kernel subsystems
along host/bmc lines? Doesn't feel intuitive, it's all Linux, but maybe
we can consolidate in the future if it makes sense?
> Then again, these are also on
> separate ports (0x60 for the keyboard controller, 0xca2 for the BMC
> KCS), so they would never actually talk to one another.
Well, sort of I guess. On Power systems we don't use the keyboard
controller for IPMI or keyboards, so we're just kinda exploiting the
hardware for our own purposes.
>
> > 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.
>
> Based on what I looked up, I think you can just forget about my original
> question. We have two separate interfaces that use an Intel 8042-style
> protocol, but they don't really interact.
Right, this is still true given Power doesn't care for keyboards or
IPMI via the keyboard controllers; the two still don't interact.
Andrew
next prev parent reply other threads:[~2021-04-12 23:46 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
2021-04-09 6:42 ` Andrew Jeffery
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
2021-04-12 1:33 ` Andrew Jeffery
2021-04-12 8:48 ` Arnd Bergmann
2021-04-12 23:45 ` Andrew Jeffery [this message]
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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