Re: [PATCH v12 07/25] CXL/PCI: Move CXL DVSEC definitions into uapi/linux/pci_regs.h

[Bowman, Terry]

On 10/1/2025 10:58 AM, Jonathan Cameron wrote:
> On Thu, 25 Sep 2025 17:34:22 -0500
> Terry Bowman <terry.bowman@xxxxxxx> wrote:
>
>> The CXL DVSECs are currently defined in cxl/core/cxlpci.h. These are not
>> accessible to other subsystems.
>>
>> Change DVSEC name formatting to follow the existing PCI format in
>> pci_regs.h. The current format uses CXL_DVSEC_XYZ. Change to be PCI_DVSEC_CXL_XYZ.
>> Reuse the existing formatting.
>>
>> Update existing occurrences to match the name change.
>>
>> Update the inline documentation to refer to latest CXL spec version.
>>
>> Signed-off-by: Terry Bowman <terry.bowman@xxxxxxx>
> Maybe we discussed it in earlier versions and I've forgotten but generally renaming
> uapi defines is a non starter.
>
> I was kind of assuming lspci used these, but nope, it uses hard coded
> value of 3 and it's own defines for the fields. (A younger me even reviewed
> the patch adding those :) )
>
> https://github.com/pciutils/pciutils/blob/master/ls-ecaps.c#L1279
>
> However, that doesn't mean other code isn't already using those defines.
>
> Minimum I think would be to state here why you think we can get away with
> this change. 
>
> Personally I'd just not bother changing that one.
>
> Jonathan
>
>

Ok, I'll leave these below as-is.

#define PCI_DVSEC_CXL_PORT                             3                                   
#define PCI_DVSEC_CXL_PORT_CTL                         0x0c                                  
#define PCI_DVSEC_CXL_PORT_CTL_UNMASK_SBR              0x00000001

Terry

>> diff --git a/include/uapi/linux/pci_regs.h b/include/uapi/linux/pci_regs.h
>> index f5b17745de60..bd03799612d3 100644
>> --- a/include/uapi/linux/pci_regs.h
>> +++ b/include/uapi/linux/pci_regs.h
>> @@ -1234,9 +1234,64 @@
>>  /* Deprecated old name, replaced with PCI_DOE_DATA_OBJECT_DISC_RSP_3_TYPE */
>>  #define PCI_DOE_DATA_OBJECT_DISC_RSP_3_PROTOCOL		PCI_DOE_DATA_OBJECT_DISC_RSP_3_TYPE
>>  
>> -/* Compute Express Link (CXL r3.1, sec 8.1.5) */
>> -#define PCI_DVSEC_CXL_PORT				3
> This is a userspace header. We can't rename existing definitions
> as we have no idea who is using them.   Only option would be to
> add a comment making the old ones deprecated and adding new ones alongside.
>
>
>> -#define PCI_DVSEC_CXL_PORT_CTL				0x0c
>> -#define PCI_DVSEC_CXL_PORT_CTL_UNMASK_SBR		0x00000001
> ....
>
>> +/* CXL 3.2 8.1.5: Extensions DVSEC for Ports */
>> +#define PCI_DVSEC_CXL_PORT_EXT					3
>> +#define   PCI_DVSEC_CXL_PORT_EXT_CTL_OFFSET			0x0c
>> +#define    PCI_DVSEC_CXL_PORT_EXT_CTL_UNMASK_SBR		0x00000001