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[2001:470:b8f6:1b::1]) by smtp.gmail.com with ESMTPSA id a18sm1013020oiy.24.2021.05.21.10.30.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 21 May 2021 10:30:10 -0700 (PDT) Sender: Corey Minyard Received: from minyard.net (unknown [IPv6:2001:470:b8f6:1b:9c8f:21cb:3961:b550]) by serve.minyard.net (Postfix) with ESMTPSA id 9F583180105; Fri, 21 May 2021 17:30:08 +0000 (UTC) Date: Fri, 21 May 2021 12:30:07 -0500 From: Corey Minyard To: Andrew Jeffery 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 Message-ID: <20210521173007.GJ2921206@minyard.net> Reply-To: minyard@acm.org References: <20210510054213.1610760-1-andrew@aj.id.au> <20210510054213.1610760-11-andrew@aj.id.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210510054213.1610760-11-andrew@aj.id.au> Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org 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 > --- > 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 >