netdev - Re: [PATCH mlx5-next 1/2] PCI/TPH: Expose pcie_tph_get_st_table

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Message-ID: <be552e0e-164b-49c0-b1ea-d35d4c64e3d9@nvidia.com>
Date: Tue, 4 Nov 2025 10:26:41 +0200
From: Yishai Hadas <yishaih@...dia.com>
To: Bjorn Helgaas <helgaas@...nel.org>
CC: Leon Romanovsky <leon@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>,
	Saeed Mahameed <saeedm@...dia.com>, Tariq Toukan <tariqt@...dia.com>, "Mark
 Bloch" <mbloch@...dia.com>, Andrew Lunn <andrew+netdev@...n.ch>, "David S.
 Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, "Jakub
 Kicinski" <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	<linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<netdev@...r.kernel.org>, <linux-rdma@...r.kernel.org>, Edward Srouji
	<edwards@...dia.com>
Subject: Re: [PATCH mlx5-next 1/2] PCI/TPH: Expose pcie_tph_get_st_table_loc()

On 03/11/2025 19:28, Bjorn Helgaas wrote:
> On Mon, Nov 03, 2025 at 06:23:26PM +0200, Yishai Hadas wrote:
>> On 03/11/2025 17:43, Bjorn Helgaas wrote:
>>> On Mon, Oct 27, 2025 at 11:34:01AM +0200, Leon Romanovsky wrote:
>>>> From: Yishai Hadas <yishaih@...dia.com>
>>>>
>>>> Expose pcie_tph_get_st_table_loc() to be used by drivers as will be done
>>>> in the next patch from the series.
>>>>
>>>> Signed-off-by: Yishai Hadas <yishaih@...dia.com>
>>>> Signed-off-by: Edward Srouji <edwards@...dia.com>
>>>> Signed-off-by: Leon Romanovsky <leonro@...dia.com>
>>>> ---
>>>>    drivers/pci/tph.c       | 7 ++++---
>>>>    include/linux/pci-tph.h | 1 +
>>>>    2 files changed, 5 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/drivers/pci/tph.c b/drivers/pci/tph.c
>>>> index cc64f93709a4..8f8457ec9adb 100644
>>>> --- a/drivers/pci/tph.c
>>>> +++ b/drivers/pci/tph.c
>>>> @@ -155,7 +155,7 @@ static u8 get_st_modes(struct pci_dev *pdev)
>>>>    	return reg;
>>>>    }
>>>> -static u32 get_st_table_loc(struct pci_dev *pdev)
>>>> +u32 pcie_tph_get_st_table_loc(struct pci_dev *pdev)
>>>>    {
>>>>    	u32 reg;
>>>> @@ -163,6 +163,7 @@ static u32 get_st_table_loc(struct pci_dev *pdev)
>>>>    	return FIELD_GET(PCI_TPH_CAP_LOC_MASK, reg);
>>>>    }
>>>> +EXPORT_SYMBOL(pcie_tph_get_st_table_loc);
>>>
>>> OK by me, but I think we should add kernel-doc for the return value.
>>>
>>> With that doc added:
>>>
>>> Acked-by: Bjorn Helgaas <bhelgaas@...gle.com>
>>
>> Thanks Bjorn.
>>
>> We may add the below hunk.
>>
>> Can that work for you ?
> 
> No, because (a) it just restates the function name and doesn't say how
> to interpret the return value (you would need a PCIe spec to look it
> up) and (b) kernel-doc syntax would be "Return: " (see
> Documentation/doc-guide/kernel-doc.rst for examples).
> 

I see.

How about adding the below as part of V1 with your Acked-by: ?

diff --git a/drivers/pci/tph.c b/drivers/pci/tph.c
index 8f8457ec9adb..510173cc8b63 100644
--- a/drivers/pci/tph.c
+++ b/drivers/pci/tph.c
@@ -155,6 +155,15 @@ static u8 get_st_modes(struct pci_dev *pdev)
         return reg;
  }

+/**
+ * pcie_tph_get_st_table_loc - Return the device's ST table location
+ * @pdev: PCI device to query
+ *
+ * Return:
+ * * PCI_TPH_LOC_NONE - Not present
+ * * PCI_TPH_LOC_CAP  - Located in the TPH Requester Extended Capability
+ * * PCI_TPH_LOC_MSIX - Located in the MSI-X Table
+ */

Yishai

>> diff --git a/drivers/pci/tph.c b/drivers/pci/tph.c
>> index 8f8457ec9adb..385307a9a328 100644
>> --- a/drivers/pci/tph.c
>> +++ b/drivers/pci/tph.c
>> @@ -155,6 +155,12 @@ static u8 get_st_modes(struct pci_dev *pdev)
>>          return reg;
>>   }
>>
>> +/**
>> + * pcie_tph_get_st_table_loc - query the device for its ST table location
>> + * @pdev: PCI device to query
>> + *
>> + * Return the location of the ST table
>> + */
>>   u32 pcie_tph_get_st_table_loc(struct pci_dev *pdev)
>>   {
>>          u32 reg;
>>
>> Yishai
>>
>>>
>>>
>>>>    /*
>>>>     * Return the size of ST table. If ST table is not in TPH Requester Extended
>>>> @@ -174,7 +175,7 @@ u16 pcie_tph_get_st_table_size(struct pci_dev *pdev)
>>>>    	u32 loc;
>>>>    	/* Check ST table location first */
>>>> -	loc = get_st_table_loc(pdev);
>>>> +	loc = pcie_tph_get_st_table_loc(pdev);
>>>>    	/* Convert loc to match with PCI_TPH_LOC_* defined in pci_regs.h */
>>>>    	loc = FIELD_PREP(PCI_TPH_CAP_LOC_MASK, loc);
>>>> @@ -299,7 +300,7 @@ int pcie_tph_set_st_entry(struct pci_dev *pdev, unsigned int index, u16 tag)
>>>>    	 */
>>>>    	set_ctrl_reg_req_en(pdev, PCI_TPH_REQ_DISABLE);
>>>> -	loc = get_st_table_loc(pdev);
>>>> +	loc = pcie_tph_get_st_table_loc(pdev);
>>>>    	/* Convert loc to match with PCI_TPH_LOC_* */
>>>>    	loc = FIELD_PREP(PCI_TPH_CAP_LOC_MASK, loc);
>>>> diff --git a/include/linux/pci-tph.h b/include/linux/pci-tph.h
>>>> index 9e4e331b1603..ba28140ce670 100644
>>>> --- a/include/linux/pci-tph.h
>>>> +++ b/include/linux/pci-tph.h
>>>> @@ -29,6 +29,7 @@ int pcie_tph_get_cpu_st(struct pci_dev *dev,
>>>>    void pcie_disable_tph(struct pci_dev *pdev);
>>>>    int pcie_enable_tph(struct pci_dev *pdev, int mode);
>>>>    u16 pcie_tph_get_st_table_size(struct pci_dev *pdev);
>>>> +u32 pcie_tph_get_st_table_loc(struct pci_dev *pdev);
>>>>    #else
>>>>    static inline int pcie_tph_set_st_entry(struct pci_dev *pdev,
>>>>    					unsigned int index, u16 tag)
>>>>
>>>> -- 
>>>> 2.51.0
>>>>
>>