linux-kernel - Re: [PATCH V7 3/4] PCI: vmd: Add vmd_device

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Message-ID: <f3cf9f00-6762-25b3-1e5a-e379e25d8642@linux.intel.com>
Date:   Fri, 28 Oct 2022 14:24:13 -0700
From:   "Patel, Nirmal" <nirmal.patel@...ux.intel.com>
To:     Jonathan Derrick <jonathan.derrick@...ux.dev>,
        david.e.box@...ux.intel.com, Bjorn Helgaas <helgaas@...nel.org>
Cc:     lorenzo.pieralisi@....com, hch@...radead.org, kw@...ux.com,
        robh@...nel.org, bhelgaas@...gle.com, michael.a.bottini@...el.com,
        rafael@...nel.org, me@...ityamohan.in, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH V7 3/4] PCI: vmd: Add vmd_device_data

On 10/28/2022 2:14 PM, Jonathan Derrick wrote:
>
> On 10/28/2022 3:22 PM, David E. Box wrote:
>> On Fri, 2022-10-28 at 14:40 -0500, Bjorn Helgaas wrote:
>>> On Fri, Oct 28, 2022 at 02:18:48PM -0500, Jonathan Derrick wrote:
>>>> On 10/28/2022 2:13 PM, Bjorn Helgaas wrote:
>>>>> On Mon, Oct 24, 2022 at 05:44:10PM -0700, David E. Box wrote:
>>>>>> Add vmd_device_data to allow adding additional info for driver data.
>>>>>>  	{PCI_VDEVICE(INTEL, PCI_DEVICE_ID_INTEL_VMD_9A0B),
>>>>>> -		.driver_data = VMD_FEAT_HAS_MEMBAR_SHADOW_VSCAP |
>>>>>> -				VMD_FEAT_HAS_BUS_RESTRICTIONS |
>>>>>> -				VMD_FEAT_OFFSET_FIRST_VECTOR,},
>>>>>> +		(kernel_ulong_t)&(struct vmd_device_data) {
>>>>>> +			.features = VMD_FEAT_HAS_MEMBAR_SHADOW_VSCAP |
>>>>>> +				    VMD_FEAT_HAS_BUS_RESTRICTIONS |
>>>>>> +				    VMD_FEAT_OFFSET_FIRST_VECTOR,
>>>>>> +		},
>>>>>> +	},
>>>>> It looks like these devices come in families where several device IDs
>>>>> share the same features.  I think this would be more readable if you
>>>>> defined each family outside this table and simply referenced the
>>>>> family here.  E.g., you could do something like:
>>>>>
>>>>>   static struct vmd_device_data vmd_v1 = {
>>>>>     .features = VMD_FEAT_HAS_MEMBAR_SHADOW_VSCAP |
>>>>> 		VMD_FEAT_HAS_BUS_RESTRICTIONS |
>>>>> 		VMD_FEAT_OFFSET_FIRST_VECTOR,
>>>>>   };
>>>> I seem to recall it being similar to this in one of the previous revisions
>>>> It's fine with me either way
>>> Indeed it was:
>>> https://lore.kernel.org/r/366a9602-555f-7a1b-a8db-bbcbf84b7b08@linux.dev
>>> I'd forgotten that.
>>>
>>> At the time there were four devices (0x467f 0x4c3d 0xa77f 0x9a0b)
>>> that used the 467f data.  The current series adds two more (0x7d0b
>>> 0x0ad0b).  Maybe the "vmd_467f_data" name could have been more
>>> descriptive, but the code was definitely shorter:
>>>
>>>   +     { PCI_VDEVICE(INTEL, 0x467f), (kernel_ulong_t)&vmd_467f_data },
>>>   +     { PCI_VDEVICE(INTEL, 0x4c3d), (kernel_ulong_t)&vmd_467f_data },
>>>   +     { PCI_VDEVICE(INTEL, 0xa77f), (kernel_ulong_t)&vmd_467f_data },
>>>   +     { PCI_VDEVICE(INTEL, PCI_DEVICE_ID_INTEL_VMD_9A0B),
>>> (kernel_ulong_t)&vmd_467f_data },
>> I prefer this too but don't know what's the best name. Could just be by the
>> platform that started this grouping, e.g. vmd_tgl_data for Tiger Lake. What do
>> you think Jonathan?
>>
>> David
> vmd_client_data ? (meaning product class; client vs enterprise)
Product class would make sense. We can keep adding new IDs.
>
>>> I do wish pci_device_id.driver_data were a void pointer, as it is for
>>> of_device_id, which makes it much more natural to express [1], but
>>> that ship has long sailed.
>>>
>>> [1] 
>>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/pci/controller/dwc/pcie-kirin.c?id=v6.0#n768
>>>
>>>>>   {PCI_VDEVICE(INTEL, PCI_DEVICE_ID_INTEL_VMD_9A0B),
>>>>>     .driver_data = (kernel_ulong_t) &vmd_v1,
>>>>>
>>>>> Then you can add VMD_FEAT_BIOS_PM_QUIRK and the .ltr value in one place
>>>>> instead of repeating it a half dozen times.
>>>>>
>>>>>>  	{0,}
>>>>>>  };
>>>>>>  MODULE_DEVICE_TABLE(pci, vmd_ids);
>>>>>> -- 
>>>>>> 2.25.1
>>>>>>