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From: Corey Minyard <minyard@acm.org>
To: Andrew Jeffery <andrew@aj.id.au>
Cc: openipmi-developer@lists.sourceforge.net,
	openbmc@lists.ozlabs.org, devicetree@vger.kernel.org,
	tmaimon77@gmail.com, linux-aspeed@lists.ozlabs.org,
	avifishman70@gmail.com, venture@google.com,
	linux-kernel@vger.kernel.org, tali.perry1@gmail.com,
	robh+dt@kernel.org, chiawei_wang@aspeedtech.com,
	linux-arm-kernel@lists.infradead.org, benjaminfair@google.com,
	arnd@arndb.de, zweiss@equinix.com
Subject: Re: [PATCH v3 10/16] ipmi: kcs_bmc: Don't enforce single-open policy in the kernel
Date: Fri, 21 May 2021 12:30:07 -0500	[thread overview]
Message-ID: <20210521173007.GJ2921206@minyard.net> (raw)
In-Reply-To: <20210510054213.1610760-11-andrew@aj.id.au>

On Mon, May 10, 2021 at 03:12:07PM +0930, 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.

I don't understand why you want to allow this.  If the second open won't
work right, then why allow it?  Why remove code that causes the second
open to error?

-corey

> 
> 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 7081541bb6ce..ad9ff13ba831 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);
>  irqreturn_t kcs_bmc_handle_event(struct kcs_bmc_device *kcs_bmc)
>  {
>  	struct kcs_bmc_client *client;
> -	irqreturn_t rc;
> +	irqreturn_t rc = IRQ_NONE;
>  
>  	spin_lock(&kcs_bmc->lock);
>  	client = kcs_bmc->client;
> -	if (client) {
> +	if (client)
>  		rc = client->ops->event(client);
> -	} 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 = IRQ_HANDLED;
> -		} else {
> -			rc = IRQ_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;
>  }
>  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 8b223e58d900..8a0b1e18e945 100644
> --- a/drivers/char/ipmi/kcs_bmc_aspeed.c
> +++ b/drivers/char/ipmi/kcs_bmc_aspeed.c
> @@ -414,8 +414,7 @@ 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);
>  
>  	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 f8b7162fb830..ab4a8caf1270 100644
> --- a/drivers/char/ipmi/kcs_bmc_npcm7xx.c
> +++ b/drivers/char/ipmi/kcs_bmc_npcm7xx.c
> @@ -202,8 +202,7 @@ 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:[~2021-05-21 17:32 UTC|newest]

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-10  5:41 [PATCH v3 00/16] ipmi: Allow raw access to KCS devices Andrew Jeffery
2021-05-10  5:41 ` [PATCH v3 01/16] ipmi: kcs_bmc_aspeed: Use of match data to extract KCS properties Andrew Jeffery
2021-05-21  7:17   ` Zev Weiss
2021-05-10  5:41 ` [PATCH v3 02/16] ipmi: kcs_bmc: Make status update atomic Andrew Jeffery
2021-05-10  5:42 ` [PATCH v3 03/16] ipmi: kcs_bmc: Rename {read, write}_{status, data}() functions Andrew Jeffery
2021-05-10  5:42 ` [PATCH v3 04/16] ipmi: kcs_bmc: Split out kcs_bmc_cdev_ipmi Andrew Jeffery
2021-05-10  5:42 ` [PATCH v3 05/16] ipmi: kcs_bmc: Turn the driver data-structures inside-out Andrew Jeffery
2021-05-21 17:14   ` Corey Minyard
2021-05-24  0:53     ` Andrew Jeffery
2021-05-24 15:41       ` [Openipmi-developer] " Corey Minyard
2021-05-25  0:12         ` Andrew Jeffery
2021-05-10  5:42 ` [PATCH v3 06/16] ipmi: kcs_bmc: Split headers into device and client Andrew Jeffery
2021-05-21  7:18   ` Zev Weiss
2021-05-10  5:42 ` [PATCH v3 07/16] ipmi: kcs_bmc: Strip private client data from struct kcs_bmc Andrew Jeffery
2021-05-21  7:18   ` Zev Weiss
2021-05-10  5:42 ` [PATCH v3 08/16] ipmi: kcs_bmc: Decouple the IPMI chardev from the core Andrew Jeffery
2021-05-21  7:19   ` Zev Weiss
2021-05-10  5:42 ` [PATCH v3 09/16] ipmi: kcs_bmc: Allow clients to control KCS IRQ state Andrew Jeffery
2021-05-21  7:19   ` Zev Weiss
2021-05-10  5:42 ` [PATCH v3 10/16] ipmi: kcs_bmc: Don't enforce single-open policy in the kernel Andrew Jeffery
2021-05-21 17:30   ` Corey Minyard [this message]
2021-05-24  0:39     ` Andrew Jeffery
2021-05-10  5:42 ` [PATCH v3 11/16] ipmi: kcs_bmc: Add serio adaptor Andrew Jeffery
2021-05-21  7:20   ` Zev Weiss
2021-06-08  0:37     ` Andrew Jeffery
2021-05-10  5:42 ` [PATCH v3 12/16] dt-bindings: ipmi: Convert ASPEED KCS binding to schema Andrew Jeffery
2021-05-10  5:42 ` [PATCH v3 13/16] dt-bindings: ipmi: Add optional SerIRQ property to ASPEED KCS devices Andrew Jeffery
2021-05-10  5:42 ` [PATCH v3 14/16] ipmi: kcs_bmc_aspeed: Implement KCS SerIRQ configuration Andrew Jeffery
2021-05-21  7:21   ` Zev Weiss
2021-06-08  0:41     ` Andrew Jeffery
2021-06-08  0:55       ` Andrew Jeffery
2021-05-10  5:42 ` [PATCH v3 15/16] ipmi: kcs_bmc_aspeed: Fix IBFIE typo from datasheet Andrew Jeffery
2021-05-10  5:42 ` [PATCH v3 16/16] ipmi: kcs_bmc_aspeed: Optionally apply status address Andrew Jeffery
2021-05-20  6:51 ` [PATCH v3 00/16] ipmi: Allow raw access to KCS devices Andrew Jeffery
2021-05-20 13:33   ` Corey Minyard
2021-05-21 17:36 ` Corey Minyard
2021-05-24  0:36   ` Andrew Jeffery

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