netdev - Re: [PATCH V9 4/8] PCI/sysfs: Add a 10-Bit Tag sysfs file PCIe Endpoint devices

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Date:   Thu, 23 Sep 2021 19:06:30 +0800
From:   Dongdong Liu <liudongdong3@...wei.com>
To:     Krzysztof Wilczyński <kw@...ux.com>
CC:     <helgaas@...nel.org>, <hch@...radead.org>, <logang@...tatee.com>,
        <leon@...nel.org>, <linux-pci@...r.kernel.org>,
        <rajur@...lsio.com>, <hverkuil-cisco@...all.nl>,
        <linux-media@...r.kernel.org>, <netdev@...r.kernel.org>
Subject: Re: [PATCH V9 4/8] PCI/sysfs: Add a 10-Bit Tag sysfs file PCIe
 Endpoint devices

Hi Krzysztof

Many thanks for your review.
On 2021/9/23 12:21, Krzysztof Wilczyński wrote:
> Hi,
>
> Thank you for sending the patch over!  A few small comments below.
>
> [...]
>> +static ssize_t pci_10bit_tag_store(struct device *dev,
>> +				   struct device_attribute *attr,
>> +				   const char *buf, size_t count)
>> +{
>> +	struct pci_dev *pdev = to_pci_dev(dev);
>> +	bool enable;
>
> Would you mind adding the following capabilities check here?
OK, will do.
>
> 	if (!capable(CAP_SYS_ADMIN))
> 		return -EPERM;
>
> This is so we make sure that whatever user is going to use this sysfs
> attribute actually has enough permissions to update this value safely.
>
>> +	if (kstrtobool(buf, &enable) < 0)
>> +		return -EINVAL;
>> +
>> +	if (pdev->driver)
>> +		return -EBUSY;
>> +
>> +	if (enable) {
>> +		if (!pcie_rp_10bit_tag_cmp_supported(pdev))
>> +			return -EPERM;
>
> Would it make sense to also verify 10-Bit Tag Completer support on the
> "disable" path too?   We won't be able to set a value if there is no
> support, but nothing will stop us from clearing it regardless - unless
> this would be safe to do?  What do you think?
Seems make sense, Will do. It is better do the same thing on the
"disable" path too.
>
>> +		pcie_capability_set_word(pdev, PCI_EXP_DEVCTL2,
>> +				PCI_EXP_DEVCTL2_10BIT_TAG_REQ_EN);
>> +	} else {
>> +		pcie_capability_clear_word(pdev, PCI_EXP_DEVCTL2,
>> +				   PCI_EXP_DEVCTL2_10BIT_TAG_REQ_EN);
>> +	}
>> +
>> +	return count;
>> +}
>
> [...]
>> +> +static umode_t pcie_dev_10bit_tag_attrs_are_visible(struct kobject *kobj,
>> +					  struct attribute *a, int n)
>
> The preferred function name for the .is_visible() callback in a case when
> there is only a single sysfs attribute being added would be:
>
>   pcie_dev_10bit_tag_attr_is_visible()
Will fix.

Thanks,
Dongdong
>
> Albeit, I appreciate that you followed the existing naming pattern.
>
> 	Krzysztof
> .
>