linux-kernel - Re: [PATCH v2 1/4] skd: Prefer pcie_capability_read

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Message-ID: <BYAPR04MB5816EDC3676A964C2D1D874BE74D0@BYAPR04MB5816.namprd04.prod.outlook.com>
Date:   Mon, 18 Nov 2019 01:45:33 +0000
From:   Damien Le Moal <Damien.LeMoal@....com>
To:     Frederick Lawler <fred@...dlawl.com>,
        "axboe@...nel.dk" <axboe@...nel.dk>
CC:     "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "bvanassche@....org" <bvanassche@....org>
Subject: Re: [PATCH v2 1/4] skd: Prefer pcie_capability_read_word()

On 2019/11/18 9:21, Frederick Lawler wrote:
> Commit 8c0d3a02c130 ("PCI: Add accessors for PCI Express Capability")
> added accessors for the PCI Express Capability so that drivers didn't
> need to be aware of differences between v1 and v2 of the PCI
> Express Capability.
> 
> Replace pci_read_config_word() and pci_write_config_word() calls with
> pcie_capability_read_word() and pcie_capability_write_word().
> 
> Signed-off-by: Frederick Lawler <fred@...dlawl.com>
> ---
>  drivers/block/skd_main.c | 8 ++------
>  1 file changed, 2 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/block/skd_main.c b/drivers/block/skd_main.c
> index 51569c199a6c..f25f6ef6b4c7 100644
> --- a/drivers/block/skd_main.c
> +++ b/drivers/block/skd_main.c
> @@ -3134,18 +3134,14 @@ MODULE_DEVICE_TABLE(pci, skd_pci_tbl);
>  
>  static char *skd_pci_info(struct skd_device *skdev, char *str)
>  {
> -	int pcie_reg;
> -
>  	strcpy(str, "PCIe (");
> -	pcie_reg = pci_find_capability(skdev->pdev, PCI_CAP_ID_EXP);
>  
> -	if (pcie_reg) {
> +	if (pci_is_pcie(skdev->pdev)) {

Maybe return early here ? The reason is that if pci_is_pcie() is false,
then the string "PCIe (" is not terminated with a closing parenthesis.
So something like:

	if (!pci_is_pcie(skdev->pdev)) {
		strcat(str, ")");
		return str;
	}

May be better. Note that the "return str" is also rather pointless since
it is not used by the caller of skd_pci_info().

>  
>  		char lwstr[6];
>  		uint16_t pcie_lstat, lspeed, lwidth;
>  
> -		pcie_reg += 0x12;
> -		pci_read_config_word(skdev->pdev, pcie_reg, &pcie_lstat);
> +		pcie_capability_read_word(skdev->pdev, 0x12, &pcie_lstat);
>  		lspeed = pcie_lstat & (0xF);
>  		lwidth = (pcie_lstat & 0x3F0) >> 4;
>  
> 


-- 
Damien Le Moal
Western Digital Research