linux-kernel - Re: [PATCH v11 3/5] PCI: Move pci_clear_and_set

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Date:   Mon, 27 Nov 2023 09:34:05 +0800
From:   Shuai Xue <xueshuai@...ux.alibaba.com>
To:     Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
        Bjorn Helgaas <helgaas@...nel.org>
Cc:     ilkka@...amperecomputing.com, kaishen@...ux.alibaba.com,
        yangyicong@...wei.com, will@...nel.org,
        Jonathan.Cameron@...wei.com, baolin.wang@...ux.alibaba.com,
        robin.murphy@....com, chengyou@...ux.alibaba.com,
        LKML <linux-kernel@...r.kernel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-pci@...r.kernel.org,
        rdunlap@...radead.org, mark.rutland@....com,
        zhuo.song@...ux.alibaba.com, renyu.zj@...ux.alibaba.com
Subject: Re: [PATCH v11 3/5] PCI: Move pci_clear_and_set_dword() helper to PCI
 header

+ Bjorn for PCI.

On 2023/11/22 21:14, Ilpo Järvinen wrote:

Hi, Ilpo,

Thank you for your reply. Please see my comments inline.


> On Tue, 21 Nov 2023, Shuai Xue wrote:
> 
>> The clear and set pattern is commonly used for accessing PCI config,
>> move the helper pci_clear_and_set_dword() from aspm.c into PCI header.
>> In addition, rename to pci_clear_and_set_config_dword() to retain the
>> "config" information and match the other accessors.
>>
>> No functional change intended.
>>
>> Signed-off-by: Shuai Xue <xueshuai@...ux.alibaba.com>
>> Acked-by: Bjorn Helgaas <bhelgaas@...gle.com>
>> Tested-by: Ilkka Koskinen <ilkka@...amperecomputing.com>
>> ---
>>  drivers/pci/access.c    | 12 ++++++++
>>  drivers/pci/pcie/aspm.c | 65 +++++++++++++++++++----------------------
>>  include/linux/pci.h     |  2 ++
>>  3 files changed, 44 insertions(+), 35 deletions(-)
>>
>> diff --git a/drivers/pci/access.c b/drivers/pci/access.c
>> index 6554a2e89d36..6449056b57dd 100644
>> --- a/drivers/pci/access.c
>> +++ b/drivers/pci/access.c
>> @@ -598,3 +598,15 @@ int pci_write_config_dword(const struct pci_dev *dev, int where,
>>  	return pci_bus_write_config_dword(dev->bus, dev->devfn, where, val);
>>  }
>>  EXPORT_SYMBOL(pci_write_config_dword);
>> +
>> +void pci_clear_and_set_config_dword(const struct pci_dev *dev, int pos,
>> +				    u32 clear, u32 set)
> 
> Just noting that annoyingly the ordering within the name is inconsistent 
> between:
>   pci_clear_and_set_config_dword()
> and
>   pcie_capability_clear_and_set_dword()
> 
> And if changed, it would be again annoyingly inconsistent with 
> pci_read/write_config_*(), oh well... And renaming pci_read/write_config_* 
> into the hierarchical pci_config_read/write_*() form for would touch only 
> ~6k lines... ;-D

I think it is a good question, but I don't have a clear answer. I don't
know much about the name history.  As you mentioned, the above two
accessors are the foundation operation, may it comes to @Bjorn decision.

The pci_clear_and_set_config_dword() is a variant of bellow pci accessors:

    pci_read_config_dword()
    pci_write_config_dword()

At last, they are consistend :)

> 
>> +		pci_clear_and_set_config_dword(child,
>> +					       child->l1ss + PCI_L1SS_CTL1, 0,
>> +					       cl1_2_enables);
> 
> Adding clear and set only variants into the header like there are for 
> pcie_capability_*() would remove the need to add those 0 parameters.
> IMO, it improves code readability considerably.
> 

Agreed.


Best Regards,
Shuai