Re: [RFC] igb_uio: deprecate iomem and ioport mapping

["Tan, Jianfeng" <jianfeng.tan@intel.com>]

Hi David,

Thank you for reviewing this.

On 9/9/2016 5:06 PM, David Marchand wrote:
> Hello Jianfeng,
>
> On Thu, Sep 1, 2016 at 4:16 AM, Jianfeng Tan <jianfeng.tan@intel.com> wrote:
>> Previously in igb_uio, iomem is mapped, and both ioport and io mem
>> are recorded into uio framework, which is duplicated and makes the
>> code too complex.
>>
>> For iomem, DPDK user space code never opens or reads files under
>> /sys/pci/bus/devices/xxxx:xx:xx.x/uio/uioY/maps/. Instead,
>> /sys/pci/bus/devices/xxxx:xx:xx.x/resourceY are used to map device
>> memory.
>>
>> For ioport, non-x86 platforms cannot read from files under
>> /sys/pci/bus/devices/xxxx:xx:xx.x/uio/uioY/portio/ directly, because
>> non-x86 platforms need to map port region for access in user space,
>> see non-x86 version pci_uio_ioport_map(). x86 platforms can use the
>> the same way as uio_pci_generic.
>>
>> This patch deprecates iomem and ioport mapping in igb_uio kernel
>> module, and adjusts the iomem implementation in both igb_uio and
>> uio_pci_generic:
>>    - for x86 platform, get ports info from /proc/ioports;
>>    - for non-x86 platform, map and get ports info by pci_uio_ioport_map().
>>
>> Note: this will affect those applications who are using files under
>> /sys/pci/bus/devices/xxxx:xx:xx.x/uio/uioY/maps/ and
>> /sys/pci/bus/devices/xxxx:xx:xx.x/uio/uioY/portio/.
>>
>> Signed-off-by: Jianfeng Tan <jianfeng.tan@intel.com>
>> ---
>>   lib/librte_eal/linuxapp/eal/eal_pci.c     |   4 -
>>   lib/librte_eal/linuxapp/eal/eal_pci_uio.c |  56 +-------------
>>   lib/librte_eal/linuxapp/igb_uio/igb_uio.c | 119 ++----------------------------
>>   3 files changed, 9 insertions(+), 170 deletions(-)
> [snip]
>
>> diff --git a/lib/librte_eal/linuxapp/eal/eal_pci_uio.c b/lib/librte_eal/linuxapp/eal/eal_pci_uio.c
>> index 1786b75..28d09ed 100644
>> --- a/lib/librte_eal/linuxapp/eal/eal_pci_uio.c
>> +++ b/lib/librte_eal/linuxapp/eal/eal_pci_uio.c
> [snip]
>
>> -       /* FIXME only for primary process ? */
>> -       if (dev->intr_handle.type == RTE_INTR_HANDLE_UNKNOWN) {
>> -
>> -               snprintf(filename, sizeof(filename), "/dev/uio%u", uio_num);
>> -               dev->intr_handle.fd = open(filename, O_RDWR);
>> -               if (dev->intr_handle.fd < 0) {
>> -                       RTE_LOG(ERR, EAL, "Cannot open %s: %s\n",
>> -                               filename, strerror(errno));
>> -                       return -1;
>> -               }
>> -               dev->intr_handle.type = RTE_INTR_HANDLE_UIO;
>> -       }
> The only potential issue I can see removing this is that if a device
> has no iomem resource, then its interrupt fd will never be
> initialised.

I'm catching it completely. IMO, dev->intr_handle.fd will be bound to be 
initialized in pci_uio_alloc_resource() <- pci_uio_map_resource() <- 
rte_eal_pci_map_device() after this patch, just like what we've done 
with uio-pci-generic. Or I'm missing something?

> I can see no problem at the moment, so let's go with this.
> If such a problem arises later, we can separate this from the resource
> mapping stuff (with a new api ?).
> The rest looks good to me.
>
> As Ferruh said, this should go through deprecation notices then go in 17.02.
>
Yes, no problem.

Thanks,
Jianfeng