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Subject: Re: [PATCH 1/2] USB:ehci:Add a whitelist for EHCI controllers
To:     Greg KH <gregkh@linuxfoundation.org>
CC:     <mathias.nyman@intel.com>, <stern@rowland.harvard.edu>,
        <liudongdong3@huawei.com>, <linux-usb@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>, <kong.kongxinwei@hisilicon.com>,
        <yisen.zhuang@huawei.com>
References: <1617873073-37371-1-git-send-email-liulongfang@huawei.com>
 <1617873073-37371-2-git-send-email-liulongfang@huawei.com>
 <YG7LO2DJMThbeJ5W@kroah.com>
From:   liulongfang <liulongfang@huawei.com>
Message-ID: <13446834-afc5-e713-d232-36c771059712@huawei.com>
Date:   Thu, 8 Apr 2021 21:04:17 +0800
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On 2021/4/8 17:22, Greg KH Wrote:
> On Thu, Apr 08, 2021 at 05:11:12PM +0800, Longfang Liu wrote:
>> Some types of EHCI controllers do not have SBRN registers.
>> By comparing the white list, the operation of reading the SBRN
>> registers is skipped.
>>
>> Subsequent EHCI controller types without SBRN registers can be
>> directly added to the white list.
>>
>> The current patch does not affect the drive function.
>>
>> Signed-off-by: Longfang Liu <liulongfang@huawei.com>
>> ---
>>  drivers/usb/host/ehci-pci.c | 27 +++++++++++++++++++++++----
>>  1 file changed, 23 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/usb/host/ehci-pci.c b/drivers/usb/host/ehci-pci.c
>> index 3c3820a..6a30afa 100644
>> --- a/drivers/usb/host/ehci-pci.c
>> +++ b/drivers/usb/host/ehci-pci.c
>> @@ -47,6 +47,28 @@ static inline bool is_bypassed_id(struct pci_dev *pdev)
>>  	return !!pci_match_id(bypass_pci_id_table, pdev);
>>  }
>>  
>> +static const struct usb_nosbrn_whitelist_entry {
>> +	unsigned short vendor;
>> +	unsigned short device;
> 
> u16 here please.
> 
>> +} usb_nosbrn_whitelist[] = {
>> +	/* STMICRO ConneXT has no sbrn register */
>> +	{PCI_VENDOR_ID_STMICRO, PCI_DEVICE_ID_STMICRO_USB_HOST},
>> +	{}
> 
> trailing , please.
> 

Is it necessary to add "," at the end here?

>> +};
>> +
>> +static bool usb_nosbrn_whitelist_check(struct pci_dev *pdev)
>> +{
>> +	const struct usb_nosbrn_whitelist_entry *entry;
>> +
>> +	for (entry = usb_nosbrn_whitelist; entry->vendor; entry++) {
>> +		if (pdev->vendor == entry->vendor &&
>> +		    pdev->device == entry->device)
>> +			return true;
>> +	}
>> +
>> +	return false;
>> +}
>> +
>>  /*
>>   * 0x84 is the offset of in/out threshold register,
>>   * and it is the same offset as the register of 'hostpc'.
>> @@ -288,10 +310,7 @@ static int ehci_pci_setup(struct usb_hcd *hcd)
>>  	}
>>  
>>  	/* Serial Bus Release Number is at PCI 0x60 offset */
>> -	if (pdev->vendor == PCI_VENDOR_ID_STMICRO
>> -	    && pdev->device == PCI_DEVICE_ID_STMICRO_USB_HOST)
>> -		;	/* ConneXT has no sbrn register */
>> -	else
>> +	if (!usb_nosbrn_whitelist_check(pdev))
> 
> Doing this as a "negative" is hard to understand.  Should this just be:
> 	forbid_sbrn_read()
> or something like that?
> 
> The term "whitelist" is not a good thing to use as it does not really
> explain anything here.
> 
> thanks,
> 
> greg k-h
> .
> 
Thanks
Longfang.