netdev - Re: [PATCH] net/mlx4_core: match pci_device

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Message-ID: <CAErSpo4yj+31puKhnxJ9Dns4c-1cWoUxxQt+OTDQDCGuuksOAw@mail.gmail.com>
Date:	Wed, 2 Apr 2014 12:28:46 -0600
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Wei Yang <weiyang@...ux.vnet.ibm.com>
Cc:	netdev <netdev@...r.kernel.org>, yevgenyp@...lanox.com,
	Or Gerlitz <ogerlitz@...lanox.com>,
	Amir Vadai <amirv@...lanox.com>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	David Miller <davem@...emloft.net>
Subject: Re: [PATCH] net/mlx4_core: match pci_device_id including dynids

On Mon, Mar 31, 2014 at 10:36 PM, Wei Yang <weiyang@...ux.vnet.ibm.com> wrote:
> Fix issue introduced by commit: 97a5221 "net/mlx4_core: pass
> pci_device_id.driver_data to __mlx4_init_one during reset".
>
> pci_match_id() just match the static pci_device_id, which may return NULL if
> someone binds the driver to a device manually using
> /sys/bus/pci/drivers/.../new_id.
>
> This patch match pci_device_id with pci_match_device() to cover both dynids
> and static id_table.
>
> Thanks to Bjorn finding this issue.

I didn't actually find it; I just passed along an issue found by
Coverity.  I usually include "Found by Coverity (CID 1194947)" in the
changelog in case anybody is trying to manage those issues.

> CC: Bjorn Helgaas <bhelgaas@...gle.com>
> CC: Amir Vadai <amirv@...lanox.com>
> Signed-off-by: Wei Yang <weiyang@...ux.vnet.ibm.com>
> Acked-by: Amir Vadai <amirv@...lanox.com>
> ---
>  drivers/net/ethernet/mellanox/mlx4/main.c |    4 +++-
>  drivers/pci/pci-driver.c                  |    3 ++-
>  include/linux/pci.h                       |    2 ++
>  3 files changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/ethernet/mellanox/mlx4/main.c b/drivers/net/ethernet/mellanox/mlx4/main.c
> index aa54ef7..b0edb5c 100644
> --- a/drivers/net/ethernet/mellanox/mlx4/main.c
> +++ b/drivers/net/ethernet/mellanox/mlx4/main.c
> @@ -2673,7 +2673,9 @@ static pci_ers_result_t mlx4_pci_slot_reset(struct pci_dev *pdev)
>         const struct pci_device_id *id;
>         int ret;
>
> -       id = pci_match_id(mlx4_pci_table, pdev);
> +       id = pci_match_device(pci_dev_driver(pdev), pdev);
> +       BUG_ON(!id);

This doesn't seem like the best solution to me, because it basically
duplicates part of __pci_device_probe() in the driver.  And of course,
I'd rather not export pci_match_device() if we can avoid it (I don't
have a specific objection; just the general "don't export more than
necessary" rule, and something with a single user always makes me look
twice).

I looked at all the .error_detected() methods in the tree, and I think
mlx4_pci_err_detected() is the only one that actually throws away the
pci_drvdata().  Most drivers just do pci_disable_device() and some
other housekeeping.  Can you do something similar?

The mlx4 approach of completely tearing down and rebuilding the device
*is* sort of appealing because I'm a little dubious of assuming that
any driver setup done before the reset is still valid afterwards.  But
maybe you could at least hang onto the pci_device_id.driver_data
value?  As far as the PCI core is concerned, it supplied that to the
.probe() function, and nothing has changed since then, so there's no
reason for a driver to request it again.

Bjorn

>         ret = __mlx4_init_one(pdev, id->driver_data);
>
>         return ret ? PCI_ERS_RESULT_DISCONNECT : PCI_ERS_RESULT_RECOVERED;
> diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
> index 25f0bc6..1ee26a1 100644
> --- a/drivers/pci/pci-driver.c
> +++ b/drivers/pci/pci-driver.c
> @@ -225,7 +225,7 @@ const struct pci_device_id *pci_match_id(const struct pci_device_id *ids,
>   * system is in its list of supported devices.  Returns the matching
>   * pci_device_id structure or %NULL if there is no match.
>   */
> -static const struct pci_device_id *pci_match_device(struct pci_driver *drv,
> +const struct pci_device_id *pci_match_device(struct pci_driver *drv,
>                                                     struct pci_dev *dev)
>  {
>         struct pci_dynid *dynid;
> @@ -1355,6 +1355,7 @@ postcore_initcall(pci_driver_init);
>
>  EXPORT_SYMBOL_GPL(pci_add_dynid);
>  EXPORT_SYMBOL(pci_match_id);
> +EXPORT_SYMBOL(pci_match_device);
>  EXPORT_SYMBOL(__pci_register_driver);
>  EXPORT_SYMBOL(pci_unregister_driver);
>  EXPORT_SYMBOL(pci_dev_driver);
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 44f6883..8ede1b5 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -1134,6 +1134,8 @@ int pci_add_dynid(struct pci_driver *drv,
>                   unsigned long driver_data);
>  const struct pci_device_id *pci_match_id(const struct pci_device_id *ids,
>                                          struct pci_dev *dev);
> +const struct pci_device_id *pci_match_device(struct pci_driver *drv,
> +                                                   struct pci_dev *dev);
>  int pci_scan_bridge(struct pci_bus *bus, struct pci_dev *dev, int max,
>                     int pass);
>
> --
> 1.7.9.5
>
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