linux-kernel - Re: [PATCH v1 1/1] fpga: dfl: pci: Use pci_find_vsec

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Date:   Tue, 9 Nov 2021 10:27:58 -0800
From:   Tom Rix <trix@...hat.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Moritz Fischer <mdf@...nel.org>,
        Matthew Gerlach <matthew.gerlach@...ux.intel.com>,
        linux-fpga@...r.kernel.org, linux-kernel@...r.kernel.org,
        Wu Hao <hao.wu@...el.com>, Xu Yilun <yilun.xu@...el.com>
Subject: Re: [PATCH v1 1/1] fpga: dfl: pci: Use pci_find_vsec_capability()
 when looking for DFL


On 11/9/21 10:05 AM, Andy Shevchenko wrote:
> On Tue, Nov 09, 2021 at 07:55:43AM -0800, Tom Rix wrote:
>> On 11/9/21 7:41 AM, Andy Shevchenko wrote:
>>> Currently the find_dfls_by_vsec() opens code pci_find_vsec_capability().
>>> Refactor the former to use the latter. No functional change intended.
> Thanks for review, my answers below.
>
> ...
>
>>> +	u16 voff;
>> The later use of voff in pci_read_config_dword is of type 'int', it may be
>> better to keep voff as an int.
> I don't think so. The rule of thumb that the types should match the value they
> got in the first place. In this case it's u16. Compiler will implicitly cast it
> to whatever is needed as long as the type is good for integer promotion.
>
> ...
>
>>> +	voff = pci_find_vsec_capability(dev, PCI_VENDOR_ID_INTEL, PCI_VSEC_ID_INTEL_DFLS);
>> This may be a weakness in the origin code, but intel isn't the exclusive
>> user of DFL.
> This does not change the original code. If you think so, this can be extended
> later on.

I would rather see this fixed now or explained why this isn't a problem.

Tom

>
>>>    	if (!voff) {
>>>    		dev_dbg(&pcidev->dev, "%s no DFL VSEC found\n", __func__);
>>>    		return -ENODEV;