linux-kernel - Re: [PATCH v2 1/8] [PATCH 1/8] drivers/peci: Add support for PECI bus driver core

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Message-ID: <20180221215133.GA9056@lunn.ch>
Date:   Wed, 21 Feb 2018 22:51:33 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Jae Hyun Yoo <jae.hyun.yoo@...ux.intel.com>
Cc:     joel@....id.au, andrew@...id.au, arnd@...db.de,
        gregkh@...uxfoundation.org, jdelvare@...e.com, linux@...ck-us.net,
        benh@...nel.crashing.org, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, devicetree@...r.kernel.org,
        linux-hwmon@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        openbmc@...ts.ozlabs.org
Subject: Re: [PATCH v2 1/8] [PATCH 1/8] drivers/peci: Add support for PECI
 bus driver core

> >Is there a real need to do transfers in atomic context, or with
> >interrupts disabled?
> >
> 
> Actually, no. Generally, this function will be called in sleep-able context
> so this code is for an exceptional case handling.
> 
> I'll rewrite this code like below:
> 	if (in_atomic() || irqs_disabled()) {
> 		dev_dbg(&adapter->dev,
> 			"xfer in non-sleepable context is not supported\n");
> 		return -EWOULDBLOCK;
> 	}

I would not even do that. Just add a call to
might_sleep(). CONFIG_DEBUG_ATOMIC_SLEEP will then find bad calls.

> >>+static int peci_ioctl_get_temp(struct peci_adapter *adapter, void *vmsg)
> >>+{
> >>+	struct peci_get_temp_msg *umsg = vmsg;
> >>+	struct peci_xfer_msg msg;
> >>+	int rc;
> >>+
> >
> >Is this getting the temperature?
> >
> 
> Yes, this is getting the 'die' temperature of a processor package.
 
So the hwmon driver provides this. No need to have both.

> >>+static long peci_ioctl(struct file *file, unsigned int iocmd, unsigned long arg)
> >>+{
> >>+	struct peci_adapter *adapter = file->private_data;
> >>+	void __user *argp = (void __user *)arg;
> >>+	unsigned int msg_len;
> >>+	enum peci_cmd cmd;
> >>+	u8 *msg;
> >>+	int rc = 0;
> >>+
> >>+	dev_dbg(&adapter->dev, "ioctl, cmd=0x%x, arg=0x%lx\n", iocmd, arg);
> >>+
> >>+	switch (iocmd) {
> >>+	case PECI_IOC_PING:
> >>+	case PECI_IOC_GET_DIB:
> >>+	case PECI_IOC_GET_TEMP:
> >>+	case PECI_IOC_RD_PKG_CFG:
> >>+	case PECI_IOC_WR_PKG_CFG:
> >>+	case PECI_IOC_RD_IA_MSR:
> >>+	case PECI_IOC_RD_PCI_CFG:
> >>+	case PECI_IOC_RD_PCI_CFG_LOCAL:
> >>+	case PECI_IOC_WR_PCI_CFG_LOCAL:
> >>+		cmd = _IOC_TYPE(iocmd) - PECI_IOC_BASE;
> >>+		msg_len = _IOC_SIZE(iocmd);
> >>+		break;
> >
> >Adding new ioctl calls is pretty frowned up. Can you export this info
> >via /sysfs?
> >
> 
> Most of these are not simple IOs so ioctl is better suited, I think.

Lets see what other reviewers say, but i think ioctls are
wrong.

     Andrew