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

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Date:   Tue, 9 Nov 2021 07:55:43 -0800
From:   Tom Rix <trix@...hat.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Moritz Fischer <mdf@...nel.org>,
        Matthew Gerlach <matthew.gerlach@...ux.intel.com>,
        linux-fpga@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     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 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.
>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> ---
>   drivers/fpga/dfl-pci.c | 17 +++++------------
>   1 file changed, 5 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/fpga/dfl-pci.c b/drivers/fpga/dfl-pci.c
> index 4d68719e608f..52b5e94db9c3 100644
> --- a/drivers/fpga/dfl-pci.c
> +++ b/drivers/fpga/dfl-pci.c
> @@ -27,7 +27,7 @@
>   #define DRV_VERSION	"0.8"
>   #define DRV_NAME	"dfl-pci"
>   
> -#define PCI_VSEC_ID_INTEL_DFLS 0x43
> +#define PCI_VSEC_ID_INTEL_DFLS	0x0043	/* FPGA Device Feature List */
>   
>   #define PCI_VNDR_DFLS_CNT 0x8
>   #define PCI_VNDR_DFLS_RES 0xc
> @@ -138,19 +138,12 @@ static int *cci_pci_create_irq_table(struct pci_dev *pcidev, unsigned int nvec)
>   
>   static int find_dfls_by_vsec(struct pci_dev *pcidev, struct dfl_fpga_enum_info *info)
>   {
> -	u32 bir, offset, vndr_hdr, dfl_cnt, dfl_res;
> -	int dfl_res_off, i, bars, voff = 0;
> +	u32 bir, offset, dfl_cnt, dfl_res;
>   	resource_size_t start, len;
> +	int dfl_res_off, i, bars;
> +	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.
>   
> -	while ((voff = pci_find_next_ext_capability(pcidev, voff, PCI_EXT_CAP_ID_VNDR))) {
> -		vndr_hdr = 0;
> -		pci_read_config_dword(pcidev, voff + PCI_VNDR_HEADER, &vndr_hdr);
> -
> -		if (PCI_VNDR_HEADER_ID(vndr_hdr) == PCI_VSEC_ID_INTEL_DFLS &&
> -		    pcidev->vendor == PCI_VENDOR_ID_INTEL)
> -			break;
> -	}
> -
> +	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.

Tom

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