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

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Date:   Mon, 18 Nov 2019 19:20:05 -0600
From:   Frederick Lawler <fred@...dlawl.com>
To:     Damien Le Moal <Damien.LeMoal@....com>
Cc:     "axboe@...nel.dk" <axboe@...nel.dk>,
        "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()

Damien Le Moal wrote on 11/17/19 7:45 PM:
> 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().
> 

I agree, but it might be better to include a note that this is not a 
PCIe device. Reading "PCIe ()" seems weird to me.

>>   
>>   		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;
>>   
>>
> 
>

Thanks,
Frederick Lawler