Re: [dpdk-dev] [PATCH v2] igb_uio: remove out-of-date comment

[Stephen Hemminger <stephen@networkplumber.org>]

On Wed, 16 Jan 2019 15:48:36 +0800
Ye Xiaolong <xiaolong.ye@intel.com> wrote:

> Hi, Stephen
> 
> On 01/15, Stephen Hemminger wrote:
> >On Wed, 16 Jan 2019 08:34:52 +0800
> >Xiaolong Ye <xiaolong.ye@intel.com> wrote:
> >  
> >> The comment for igbuio_pci_irqhandler is out of date as the code evolves,
> >> remove it to avoid misleading.
> >> 
> >> Signed-off-by: Xiaolong Ye <xiaolong.ye@intel.com>
> >> ---
> >>  kernel/linux/igb_uio/igb_uio.c | 4 ----
> >>  1 file changed, 4 deletions(-)
> >> 
> >> diff --git a/kernel/linux/igb_uio/igb_uio.c b/kernel/linux/igb_uio/igb_uio.c
> >> index 3cf394bdf..d6ac51e79 100644
> >> --- a/kernel/linux/igb_uio/igb_uio.c
> >> +++ b/kernel/linux/igb_uio/igb_uio.c
> >> @@ -185,10 +185,6 @@ igbuio_pci_irqcontrol(struct uio_info *info, s32 irq_state)
> >>  	return 0;
> >>  }
> >>  
> >> -/**
> >> - * This is interrupt handler which will check if the interrupt is for the right device.
> >> - * If yes, disable it here and will be enable later.
> >> - */
> >>  static irqreturn_t
> >>  igbuio_pci_irqhandler(int irq, void *dev_id)
> >>  {  
> >
> >The comment is partially correct; if you look at the legacy case.
> >
> >Maybe better to move the comment to pci_check_and_mask_intx in compat.h?
> >I see there is another incorrect comment there.
> >  
> 
> As I tried to understand pci_check_and_mask_intx behavior, I noticed that it 
> was introduced by commit 399a3f0d ("igb_uio: fix IRQ mode handling"), and it
> was derived from igbuio_set_interrupt_mask, however there were two parameters
> in igbuio_set_interrupt_mask as below:
> 
> 	static int
> 	igbuio_set_interrupt_mask(struct rte_uio_pci_dev *udev, int32_t state)
> 
> while the pci_check_and_mask_intx only has 1 parameter,
> 
> 	static bool pci_check_and_mask_intx(struct pci_dev *pdev)
> 
> but in its function body it still use the "state" accorrding to commit 399a3f0d
> 
> +static bool pci_check_and_mask_intx(struct pci_dev *pdev)
>  {
> -       /* Some function names changes between 3.2.0 and 3.3.0... */
> -#if LINUX_VERSION_CODE < KERNEL_VERSION(3, 3, 0)
> -       pci_unblock_user_cfg_access(pdev);
> -#else
> -       pci_cfg_access_unlock(pdev);
> -#endif
> +       bool pending;
> +       uint32_t status;
> +
> +       pci_block_user_cfg_access(dev);
> +       pci_read_config_dword(pdev, PCI_COMMAND, &status);
> +
> +       /* interrupt is not ours, goes to out */
> +       pending = (((status >> 16) & PCI_STATUS_INTERRUPT) != 0);
> +       if (pending) {
> +               uint16_t old, new;
> +
> +               old = status;
> +               if (state != 0) <=========================== state still in use
> +                       new = old & (~PCI_COMMAND_INTX_DISABLE);
> +               else
> +                       new = old | PCI_COMMAND_INTX_DISABLE;
> +
> +               if (old != new)
> +                       pci_write_config_word(pdev, PCI_COMMAND, new);
> +       }
> +       pci_unblock_user_cfg_access(dev);
> +
> +       return pending;
> 
> and later this was fixed as a typo in commit 5b2f8137 ("igb_uio: fix typos for 
> kernel older than 3.3") which seems not correct.
> 
>                 old = status;
> -               if (state != 0)
> +               if (status != 0)
> 
> I feel like that pci_check_and_mask_intx still needs two parameters from code
> point of view, please correct me if I was wrong or miss anything, or you think 
> it's sensible, I'll cook a patch for it. 
> 
> Thanks,
> Xiaolong

This code is copy of upstream kernel function, you should look at that.