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: <6c67978c-9283-6c8d-95b4-9900b3b9a810@linux.intel.com>
Date:   Wed, 21 Feb 2018 14:03:37 -0800
From:   Jae Hyun Yoo <jae.hyun.yoo@...ux.intel.com>
To:     Andrew Lunn <andrew@...n.ch>
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



On 2/21/2018 1:51 PM, Andrew Lunn wrote:
>>> 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.
> 

Thanks for the suggestion. I've learned one thing. :)

>>>> +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.
> 

This this common API in core driver of PECI bus. The hwmon is also uses 
it through peci_command call.

>>>> +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
>