Re: [dpdk-dev] [PATCH v2] igb_uio: remove out-of-date comment

[Ye Xiaolong <xiaolong.ye@intel.com>]

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 The comment for igbuio_pci_irqhandler is out of date as the code evolves,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