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From: Santosh Shukla <sshukla@mvista.com>
To: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Cc: dev@dpdk.org
Subject: Re: [dpdk-dev] [PATCH v6 1/8] eal: pci: add api to rd/wr pci bar region
Date: Tue, 2 Feb 2016 12:30:35 +0530	[thread overview]
Message-ID: <CAAyOgsYfUiECZ9b7e9TUMGT4c6A95oDAHCNwy_r=nqiPXBkvTw@mail.gmail.com> (raw)
In-Reply-To: <20160202054345.GI4257@yliu-dev.sh.intel.com>

On Tue, Feb 2, 2016 at 11:13 AM, Yuanhan Liu
<yuanhan.liu@linux.intel.com> wrote:
> On Tue, Feb 02, 2016 at 09:44:14AM +0530, Santosh Shukla wrote:
>> >> +int rte_eal_pci_read_bar(const struct rte_pci_device *device,
>> >> +                      void *buf, size_t len, off_t offset,
>> >> +                      int bar_idx)
>> >> +
>> >> +{
>> >> +     const struct rte_intr_handle *intr_handle = &device->intr_handle;
>> >
>> > I'd suggest to reference this var inside pci_vfio_read/write_bar(), and
>> > pass device as the parmater instead.
>> >
>>
>> (Sorry for late reply, I was travelling on Monday.)
>> Make sense.
>>
>> >> +
>> >> +     switch (device->kdrv) {
>> >> +     case RTE_KDRV_VFIO:
>> >> +             return pci_vfio_read_bar(intr_handle, buf, len,
>> >> +                                      offset, bar_idx);
>> >> +     default:
>> >> +             RTE_LOG(ERR, EAL, "write bar not supported by driver\n");
>> >                                    ^^^^^
>> > typo.
>> >
>>
>> Oh, r / write / read, right? sorry for typo error (:-
>
> Right.
>
>>
>> >
>> > BTW, I have a question about this API. Obviously, reading/writing bar
>> > space is supported with UIO (when memory resource is mmapped). And I
>> > know why you introduced such 2 APIs, for reading IO bar.
>> >
>> > So, here is the question: what are the 2 APIs for, for being gerneric
>> > APIs to read/write bar spaces, or just to read IO bar spaces? If it's
>> > former, the message is wrong; if it's later, you may better rename it
>> > to rte_eal_pci_read/write_io_bar()?
>> >
>>
>> 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.
>

I agree.. But if UIO doesn't and need could, then I am confused what
can be done? However we have a use-case for vfio so It make sense to
me use this api.  Or else If we all agree then I can export api only
for VFIO.. but it will violate EAL abstraction.


> Anyway, it's just some thoughts from me. David, comments?
>
>         --yliu

  parent reply	other threads:[~2016-02-02  7:00 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <0000-cover-letter.patch>
2016-01-29 18:21 ` Santosh Shukla
2016-01-29 18:21   ` [dpdk-dev] [PATCH v6 2/8] linuxapp/vfio: ignore mapping for ioport region Santosh Shukla
2016-01-29 18:21   ` [dpdk-dev] [PATCH v6 3/8] eal/linux: never check iopl for arm Santosh Shukla
2016-01-29 18:21   ` [dpdk-dev] [PATCH v6 4/8] virtio: Introduce config RTE_VIRTIO_INC_VECTOR Santosh Shukla
2016-01-29 18:21   ` [dpdk-dev] [PATCH v6 5/8] virtio: move io header and api from virtio_pci.h Santosh Shukla
2016-01-29 18:21   ` [dpdk-dev] [PATCH v6 6/8] virtio: add vfio api to rd/wr ioport space Santosh Shukla
2016-02-01 12:48     ` Yuanhan Liu
2016-02-02  4:30       ` Santosh Shukla
2016-02-02  5:19         ` Yuanhan Liu
2016-02-02  6:02           ` Santosh Shukla
2016-01-29 18:21   ` [dpdk-dev] [PATCH v6 7/8] virtio: extend pci rw api for vfio Santosh Shukla
2016-01-29 18:21   ` [dpdk-dev] [PATCH v6 8/8] virtio: do not parse if interface is vfio Santosh Shukla
2016-02-01 13:48   ` [dpdk-dev] [PATCH v6 1/8] eal: pci: add api to rd/wr pci bar region Yuanhan Liu
2016-02-02  4:14     ` Santosh Shukla
2016-02-02  5:43       ` Yuanhan Liu
2016-02-02  5:50         ` David Marchand
2016-02-02  8:49           ` Yuanhan Liu
2016-02-02 15:51             ` Santosh Shukla
2016-02-02 16:18               ` Santosh Shukla
2016-02-03  9:50                 ` Santosh Shukla
2016-02-03 11:50                   ` Yuanhan Liu
2016-02-05 17:56                     ` David Marchand
2016-02-03 11:43                 ` Yuanhan Liu
2016-02-02  7:00         ` Santosh Shukla [this message]
2016-02-02  7:01           ` Santosh Shukla
2016-02-08 10:03 ` [dpdk-dev] [PATCH v8 3/4] eal/linux: vfio: ignore mapping for ioport region Santosh Shukla
2016-02-08 10:03   ` [dpdk-dev] [PATCH v8 4/4] eal/linux: vfio: add pci ioport support Santosh Shukla
2016-02-08 14:13     ` Burakov, Anatoly
2016-02-09  9:04       ` David Marchand
2016-02-18  5:25         ` Santosh Shukla
2016-02-18 14:00           ` Thomas Monjalon

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