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From:   Damien Le Moal <Damien.LeMoal@wdc.com>
To:     Frederick Lawler <fred@fredlawl.com>
CC:     "axboe@kernel.dk" <axboe@kernel.dk>,
        "linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "bhelgaas@google.com" <bhelgaas@google.com>,
        "bvanassche@acm.org" <bvanassche@acm.org>
Subject: Re: [PATCH v2 1/4] skd: Prefer pcie_capability_read_word()
Thread-Topic: [PATCH v2 1/4] skd: Prefer pcie_capability_read_word()
Thread-Index: AQHVnaYWjyRplcnjK0O+FGDAzAO+yA==
Date:   Tue, 19 Nov 2019 02:41:45 +0000
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On 2019/11/19 10:20, Frederick Lawler wrote:=0A=
> Damien Le Moal wrote on 11/17/19 7:45 PM:=0A=
>> On 2019/11/18 9:21, Frederick Lawler wrote:=0A=
>>> Commit 8c0d3a02c130 ("PCI: Add accessors for PCI Express Capability")=
=0A=
>>> added accessors for the PCI Express Capability so that drivers didn't=
=0A=
>>> need to be aware of differences between v1 and v2 of the PCI=0A=
>>> Express Capability.=0A=
>>>=0A=
>>> Replace pci_read_config_word() and pci_write_config_word() calls with=
=0A=
>>> pcie_capability_read_word() and pcie_capability_write_word().=0A=
>>>=0A=
>>> Signed-off-by: Frederick Lawler <fred@fredlawl.com>=0A=
>>> ---=0A=
>>>   drivers/block/skd_main.c | 8 ++------=0A=
>>>   1 file changed, 2 insertions(+), 6 deletions(-)=0A=
>>>=0A=
>>> diff --git a/drivers/block/skd_main.c b/drivers/block/skd_main.c=0A=
>>> index 51569c199a6c..f25f6ef6b4c7 100644=0A=
>>> --- a/drivers/block/skd_main.c=0A=
>>> +++ b/drivers/block/skd_main.c=0A=
>>> @@ -3134,18 +3134,14 @@ MODULE_DEVICE_TABLE(pci, skd_pci_tbl);=0A=
>>>   =0A=
>>>   static char *skd_pci_info(struct skd_device *skdev, char *str)=0A=
>>>   {=0A=
>>> -	int pcie_reg;=0A=
>>> -=0A=
>>>   	strcpy(str, "PCIe (");=0A=
>>> -	pcie_reg =3D pci_find_capability(skdev->pdev, PCI_CAP_ID_EXP);=0A=
>>>   =0A=
>>> -	if (pcie_reg) {=0A=
>>> +	if (pci_is_pcie(skdev->pdev)) {=0A=
>>=0A=
>> Maybe return early here ? The reason is that if pci_is_pcie() is false,=
=0A=
>> then the string "PCIe (" is not terminated with a closing parenthesis.=
=0A=
>> So something like:=0A=
>>=0A=
>> 	if (!pci_is_pcie(skdev->pdev)) {=0A=
>> 		strcat(str, ")");=0A=
>> 		return str;=0A=
>> 	}=0A=
>>=0A=
>> May be better. Note that the "return str" is also rather pointless since=
=0A=
>> it is not used by the caller of skd_pci_info().=0A=
>>=0A=
> =0A=
> I agree, but it might be better to include a note that this is not a =0A=
> PCIe device. Reading "PCIe ()" seems weird to me.=0A=
=0A=
Yes indeed. But since this device is PCIe only, if=0A=
pci_is_pcie(skdev->pdev) =3D=3D false, we should probably fail the driver=
=0A=
initialization.=0A=
=0A=
> =0A=
>>>   =0A=
>>>   		char lwstr[6];=0A=
>>>   		uint16_t pcie_lstat, lspeed, lwidth;=0A=
>>>   =0A=
>>> -		pcie_reg +=3D 0x12;=0A=
>>> -		pci_read_config_word(skdev->pdev, pcie_reg, &pcie_lstat);=0A=
>>> +		pcie_capability_read_word(skdev->pdev, 0x12, &pcie_lstat);=0A=
>>>   		lspeed =3D pcie_lstat & (0xF);=0A=
>>>   		lwidth =3D (pcie_lstat & 0x3F0) >> 4;=0A=
>>>   =0A=
>>>=0A=
>>=0A=
>>=0A=
> =0A=
> Thanks,=0A=
> Frederick Lawler=0A=
> =0A=
> =0A=
=0A=
=0A=
-- =0A=
Damien Le Moal=0A=
Western Digital Research=0A=