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From: Zev Weiss <zweiss@equinix.com>
To: Andrew Jeffery <andrew@aj.id.au>
Cc: "openipmi-developer@lists.sourceforge.net"
	<openipmi-developer@lists.sourceforge.net>,
	"openbmc@lists.ozlabs.org" <openbmc@lists.ozlabs.org>,
	"minyard@acm.org" <minyard@acm.org>,
	"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
	"ryan_chen@aspeedtech.com" <ryan_chen@aspeedtech.com>,
	"tmaimon77@gmail.com" <tmaimon77@gmail.com>,
	"linux-aspeed@lists.ozlabs.org" <linux-aspeed@lists.ozlabs.org>,
	"avifishman70@gmail.com" <avifishman70@gmail.com>,
	"venture@google.com" <venture@google.com>,
	"linus.walleij@linaro.org" <linus.walleij@linaro.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"tali.perry1@gmail.com" <tali.perry1@gmail.com>,
	"linux-gpio@vger.kernel.org" <linux-gpio@vger.kernel.org>,
	"robh+dt@kernel.org" <robh+dt@kernel.org>,
	"lee.jones@linaro.org" <lee.jones@linaro.org>,
	"chiawei_wang@aspeedtech.com" <chiawei_wang@aspeedtech.com>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>,
	"benjaminfair@google.com" <benjaminfair@google.com>
Subject: Re: [PATCH v2 15/21] ipmi: kcs_bmc: Don't enforce single-open policy in the kernel
Date: Fri, 9 Apr 2021 05:07:11 +0000	[thread overview]
Message-ID: <YG/g/poZLwO34QH7@packtop> (raw)
In-Reply-To: <20210319062752.145730-15-andrew@aj.id.au>

On Fri, Mar 19, 2021 at 01:27:46AM CDT, Andrew Jeffery wrote:
>Soon it will be possible for one KCS device to have multiple associated
>chardevs exposed to userspace (for IPMI and raw-style access). However,
>don't prevent userspace from:
>
>1. Opening more than one chardev at a time, or
>2. Opening the same chardev more than once.
>
>System behaviour is undefined for both classes of multiple access, so
>userspace must manage itself accordingly.
>
>The implementation delivers IBF and OBF events to the first chardev
>client to associate with the KCS device. An open on a related chardev
>cannot associate its client with the KCS device and so will not
>receive notification of events. However, any fd on any chardev may race
>their accesses to the data and status registers.
>
>Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
>---
> drivers/char/ipmi/kcs_bmc.c         | 34 ++++++++++-------------------
> drivers/char/ipmi/kcs_bmc_aspeed.c  |  3 +--
> drivers/char/ipmi/kcs_bmc_npcm7xx.c |  3 +--
> 3 files changed, 14 insertions(+), 26 deletions(-)
>
>diff --git a/drivers/char/ipmi/kcs_bmc.c b/drivers/char/ipmi/kcs_bmc.c
>index 05bbb72418b2..2fafa9541934 100644
>--- a/drivers/char/ipmi/kcs_bmc.c
>+++ b/drivers/char/ipmi/kcs_bmc.c
>@@ -55,24 +55,12 @@ EXPORT_SYMBOL(kcs_bmc_update_status);
> int kcs_bmc_handle_event(struct kcs_bmc_device *kcs_bmc)
> {
> 	struct kcs_bmc_client *client;
>-	int rc;
>+	int rc = KCS_BMC_EVENT_NONE;
>
> 	spin_lock(&kcs_bmc->lock);
> 	client = kcs_bmc->client;
>-	if (client) {
>+	if (!WARN_ON_ONCE(!client))
> 		rc = client->ops->event(client);

The double-negation split by a macro seems a bit confusing to me
readability-wise; could we simplify to something like

	if (client)
		rc = client->ops->event(client);
	else
		WARN_ONCE();

?

>-	} else {
>-		u8 status;
>-
>-		status = kcs_bmc_read_status(kcs_bmc);
>-		if (status & KCS_BMC_STR_IBF) {
>-			/* Ack the event by reading the data */
>-			kcs_bmc_read_data(kcs_bmc);
>-			rc = KCS_BMC_EVENT_HANDLED;
>-		} else {
>-			rc = KCS_BMC_EVENT_NONE;
>-		}
>-	}
> 	spin_unlock(&kcs_bmc->lock);
>
> 	return rc;
>@@ -81,26 +69,28 @@ EXPORT_SYMBOL(kcs_bmc_handle_event);
>
> int kcs_bmc_enable_device(struct kcs_bmc_device *kcs_bmc, struct kcs_bmc_client *client)
> {
>-	int rc;
>-
> 	spin_lock_irq(&kcs_bmc->lock);
>-	if (kcs_bmc->client) {
>-		rc = -EBUSY;
>-	} else {
>+	if (!kcs_bmc->client) {
>+		u8 mask = KCS_BMC_EVENT_TYPE_IBF;
>+
> 		kcs_bmc->client = client;
>-		rc = 0;
>+		kcs_bmc_update_event_mask(kcs_bmc, mask, mask);
> 	}
> 	spin_unlock_irq(&kcs_bmc->lock);
>
>-	return rc;
>+	return 0;

Since this function appears to be infallible now, should it just return
void?  (Might be more churn than it's worth...shrug.)

> }
> EXPORT_SYMBOL(kcs_bmc_enable_device);
>
> void kcs_bmc_disable_device(struct kcs_bmc_device *kcs_bmc, struct kcs_bmc_client *client)
> {
> 	spin_lock_irq(&kcs_bmc->lock);
>-	if (client == kcs_bmc->client)
>+	if (client == kcs_bmc->client) {
>+		u8 mask = KCS_BMC_EVENT_TYPE_IBF | KCS_BMC_EVENT_TYPE_OBE;
>+
>+		kcs_bmc_update_event_mask(kcs_bmc, mask, 0);
> 		kcs_bmc->client = NULL;
>+	}
> 	spin_unlock_irq(&kcs_bmc->lock);
> }
> EXPORT_SYMBOL(kcs_bmc_disable_device);
>diff --git a/drivers/char/ipmi/kcs_bmc_aspeed.c b/drivers/char/ipmi/kcs_bmc_aspeed.c
>index 5f26471c038c..271845eb2e26 100644
>--- a/drivers/char/ipmi/kcs_bmc_aspeed.c
>+++ b/drivers/char/ipmi/kcs_bmc_aspeed.c
>@@ -419,8 +419,7 @@ static int aspeed_kcs_probe(struct platform_device *pdev)
>
> 	platform_set_drvdata(pdev, priv);
>
>-	aspeed_kcs_irq_mask_update(kcs_bmc, (KCS_BMC_EVENT_TYPE_IBF | KCS_BMC_EVENT_TYPE_OBE),
>-				   KCS_BMC_EVENT_TYPE_IBF);
>+	aspeed_kcs_irq_mask_update(kcs_bmc, (KCS_BMC_EVENT_TYPE_IBF | KCS_BMC_EVENT_TYPE_OBE), 0);
> 	aspeed_kcs_enable_channel(kcs_bmc, true);
>
> 	rc = kcs_bmc_add_device(&priv->kcs_bmc);
>diff --git a/drivers/char/ipmi/kcs_bmc_npcm7xx.c b/drivers/char/ipmi/kcs_bmc_npcm7xx.c
>index c2032728a03d..fdf35cad2eba 100644
>--- a/drivers/char/ipmi/kcs_bmc_npcm7xx.c
>+++ b/drivers/char/ipmi/kcs_bmc_npcm7xx.c
>@@ -207,8 +207,7 @@ static int npcm7xx_kcs_probe(struct platform_device *pdev)
> 	if (rc)
> 		return rc;
>
>-	npcm7xx_kcs_irq_mask_update(kcs_bmc, (KCS_BMC_EVENT_TYPE_IBF | KCS_BMC_EVENT_TYPE_OBE),
>-				    KCS_BMC_EVENT_TYPE_IBF);
>+	npcm7xx_kcs_irq_mask_update(kcs_bmc, (KCS_BMC_EVENT_TYPE_IBF | KCS_BMC_EVENT_TYPE_OBE), 0);
> 	npcm7xx_kcs_enable_channel(kcs_bmc, true);
>
> 	pr_info("channel=%u idr=0x%x odr=0x%x str=0x%x\n",
>-- 
>2.27.0
>
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  reply	other threads:[~2021-04-09  5:14 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 [this message]
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
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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