From: Jacob Keller <jacob.e.keller@intel.com>
To: Bjorn Helgaas <helgaas@kernel.org>
Cc: linux-pci@vger.kernel.org, netdev@vger.kernel.org,
Jeff Kirsher <jeffrey.t.kirsher@intel.com>,
QLogic-Storage-Upstream@cavium.com,
Michael Chan <michael.chan@broadcom.com>
Subject: Re: [PATCH 1/5] pci: introduce pci_get_dsn
Date: Mon, 2 Mar 2020 15:24:29 -0800 [thread overview]
Message-ID: <2fa00fef-7d11-d0b6-49a0-85a2b08a144d@intel.com> (raw)
In-Reply-To: <20200302232057.GA182308@google.com>
On 3/2/2020 3:20 PM, Bjorn Helgaas wrote:
> On Mon, Mar 02, 2020 at 02:33:12PM -0800, Jacob Keller wrote:
>> On 3/2/2020 2:25 PM, Bjorn Helgaas wrote:
>
>>>> +int pci_get_dsn(struct pci_dev *dev, u8 dsn[])
>>>> +{
>>>> + u32 dword;
>>>> + int pos;
>>>> +
>>>> +
>>>> + pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_DSN);
>>>> + if (!pos)
>>>> + return -EOPNOTSUPP;
>>>> +
>>>> + /*
>>>> + * The Device Serial Number is two dwords offset 4 bytes from the
>>>> + * capability position.
>>>> + */
>>>> + pos += 4;
>>>> + pci_read_config_dword(dev, pos, &dword);
>>>> + put_unaligned_le32(dword, &dsn[0]);
>>>> + pci_read_config_dword(dev, pos + 4, &dword);
>>>> + put_unaligned_le32(dword, &dsn[4]);
>>>
>>> Since the serial number is a 64-bit value, can we just return a u64
>>> and let the caller worry about any alignment and byte-order issues?
>>>
>>> This would be the only use of asm/unaligned.h in driver/pci, and I
>>> don't think DSN should be that special.
>>
>> I suppose that's fair, but it ends up leaving most callers having to fix
>> this immediately after calling this function.
>
> PCIe doesn't impose any structure on the value; it just says the first
> dword is the lower DW and the second is the upper DW. As long as we
> put that together correctly into a u64, I think further interpretation
> is caller-specific.
>
Makes sense. So basically, convert pci_get_dsn to a simply return a u64
instead of copying to an array, and then make callers assume that a
value of 0 is invalid?
Thanks,
Jake
next prev parent reply other threads:[~2020-03-02 23:24 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-27 22:36 [PATCH 0/5] pci: implement function to read Device Serial Number Jacob Keller
2020-02-27 22:36 ` [PATCH] ice-shared: add macro specifying max NVM offset Jacob Keller
2020-02-27 22:43 ` Jacob Keller
2020-02-27 22:36 ` [PATCH 1/5] pci: introduce pci_get_dsn Jacob Keller
2020-03-01 5:27 ` David Miller
2020-03-02 19:58 ` Jacob Keller
2020-03-02 22:25 ` Bjorn Helgaas
2020-03-02 22:33 ` Jacob Keller
2020-03-02 23:20 ` Bjorn Helgaas
2020-03-02 23:24 ` Jacob Keller [this message]
2020-03-02 23:39 ` Bjorn Helgaas
2020-03-03 2:24 ` [PATCH v2 0/6] PCI: Implement function to read Device Serial Number Jacob Keller
2020-03-03 2:25 ` [PATCH v2 1/6] PCI: Introduce pci_get_dsn Jacob Keller
2020-03-04 22:42 ` Bjorn Helgaas
2020-03-03 2:25 ` [PATCH v2 2/6] bnxt_en: Use pci_get_dsn() Jacob Keller
2020-03-03 2:25 ` [PATCH v2 3/6] scsi: qedf: " Jacob Keller
2020-03-03 2:25 ` [PATCH v2 4/6] ice: " Jacob Keller
2020-03-03 2:25 ` [PATCH v2 5/6] ixgbe: " Jacob Keller
2020-03-03 2:25 ` [PATCH v2 6/6] nfp: " Jacob Keller
2020-03-03 3:40 ` Jakub Kicinski
2020-03-03 17:36 ` Jacob Keller
2020-03-04 22:28 ` [PATCH v2 0/6] PCI: Implement function to read Device Serial Number David Miller
2020-03-06 1:30 ` David Miller
2020-02-27 22:36 ` [PATCH 2/5] bnxt_en: use pci_get_dsn Jacob Keller
2020-03-02 22:25 ` Bjorn Helgaas
2020-02-27 22:36 ` [PATCH 3/5] scsi: qedf: " Jacob Keller
2020-02-27 22:36 ` [PATCH 4/5] ice: " Jacob Keller
2020-02-27 22:36 ` [PATCH 5/5] ixgbe: " Jacob Keller
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