Re: [PATCH v6 1/8] eal: pci: add api to rd/wr pci bar region

[Santosh Shukla <sshukla@mvista.com>]

On Tue, Feb 2, 2016 at 9:48 PM, Santosh Shukla <sshukla@mvista.com> wrote:
> On Tue, Feb 2, 2016 at 9:21 PM, Santosh Shukla <sshukla@mvista.com> wrote:
>> On Tue, Feb 2, 2016 at 2:19 PM, Yuanhan Liu <yuanhan.liu@linux.intel.com> wrote:
>>> On Tue, Feb 02, 2016 at 06:50:18AM +0100, David Marchand wrote:
>>>> On Tue, Feb 2, 2016 at 6:43 AM, Yuanhan Liu <yuanhan.liu@linux.intel.com> wrote:
>>>> > On Tue, Feb 02, 2016 at 09:44:14AM +0530, Santosh Shukla wrote:
>>>> >> Current use-case is virtio: It is used as io_bar which is first
>>>> >> bar[1]. But implementation is generic, can be used to do rd/wr for
>>>> >> other bar index too. Also vfio facilitate user to do rd/wr to pci_bars
>>>> >> w/o mapping that bar, So apis will be useful for such cases in future.
>>>> >>
>>>> >> AFAIU: uio has read/write_config api only and Yes if bar region mapped
>>>> >> then no need to do rd/wr, user can directly access the pci_memory. But
>>>> >> use-case of this api entirely different: unmapped memory by
>>>> >> application context i.e.. vfio_rd/wr-way {pread/pwrite-way}.
>>>> >>
>>>> >> Is above explanation convincing? Pl. let me know.
>>>> >
>>>> > TBH, not really. So, as you stated, it should be generic APIs to
>>>> > read/write bar space, but limiting it to VFIO only and claiming
>>>> > that read/write bar space is not support by other drivers (such
>>>> > as UIO) while in fact it can (in some ways) doesn't seem right
>>>> > to me.
>>>> >
>>>> > Anyway, it's just some thoughts from me. David, comments?
>>>>
>>>> >From the very start, same opinion.
>>>> We should have a unique api to access those, and eal should hide
>>>> details like kernel drivers (uio, vfio, whatever) to the pmd.
>>>>
>>>> Now the thing is, how to do this in an elegant and efficient way.
>>>
>>> I was thinking that we may just make it be IO port specific read/
>>> write functions:
>>>
>>
>> Ok,
>>
>>>         rte_eal_pci_ioport_read(dev, bar, buf, size)
>>>         {
>>>
>>>                 return if not an IO bar;
>>>
>>>                 if (has io)
>>>                         return inb/w/l();
>>>
>>
>> In that case, It may be r / if (has io) / if (drv->kdrv == UIO)
>>
>>>                 if (vfio)
>>>                         return vfio_ioport_read();
>>>
>>>                 else, claim aloud that io port read is not allowed
>>>         }
>>>
>>> Let us not handle memory bar resource here: in such case, you should
>>> go with rte_eal_pci_map_device() and do it with memory mapped io.
>>>
>>> Does that make any sense?
>>>
>> I am not entirely sure.
>> Are you considering IGB_UIO, UIO_GENERIC and NIC_UIO: all the cases ?
>>
>
> Just came-up something below what Yuanhan has proposed, Does this look okay?
>
> int rte_eal_pci_ioport_read(const struct rte_pci_device *device,
>                                               void *buf, size_t len,
> off_t offset,
>                                               int bar_idx)
> {
>       if (bar_idx != 0) {
>               RTE_LOG(ERR, EAL, "not a ioport bar\n");
>               return -1;
>        }
>
>      switch (device->kdrv) {
>      case RTE_KDRV_VFIO:
>                return pci_vfio_ioport_read(device, buf, len, offset, bar_idx);
>      case RTE_KDRV_IGB_UIO:
>      case RTE_KDRV_UIO_GENERIC:
>      case RTE_KDRV_NIC_UIO:
>          {
>               switch (size)
>                       case 1: return inb(buf /*ioport address*/);
>                       case 2: return inw(buf /* ioport address*/);
>                       case 4: return inl(buf /* ioport address*/);
>                       default:
>                              RTE_LOG(ERR, EAL, "invalid size\n");
>           }
>
>        default:
>                  RTE_LOG(ERR, EAL, "read bar not supported by driver\n");
>                  return -1;
>       }
> }
>

Ping?

Also can someone please review rest of series. This patchset going
through multiple revision, Each revision get one / two comment, It
would help if I get review comment for each patch.

>>
>>>         --yliu