[dpdk-dev] [PATCH 8/9] pci: add a helper to refresh a device

[David Marchand]

On Wed, Feb 10, 2016 at 12:23 PM, Jan Viktorin <viktorin at rehivetech.com> wrote:
> On Fri, 29 Jan 2016 15:08:35 +0100
> David Marchand <david.marchand at 6wind.com> wrote:
>
>> It will be used mainly for hotplug code.
>>
>> Signed-off-by: David Marchand <david.marchand at 6wind.com>
>> ---
>>  lib/librte_eal/bsdapp/eal/eal_pci.c   | 49 +++++++++++++++++++++++++++++++++++
>>  lib/librte_eal/common/eal_private.h   | 13 ++++++++++
>>  lib/librte_eal/linuxapp/eal/eal_pci.c | 13 ++++++++++
>>  3 files changed, 75 insertions(+)
>>
>> diff --git a/lib/librte_eal/bsdapp/eal/eal_pci.c b/lib/librte_eal/bsdapp/eal/eal_pci.c
>> index 4584522..5dd89e3 100644
>> --- a/lib/librte_eal/bsdapp/eal/eal_pci.c
>> +++ b/lib/librte_eal/bsdapp/eal/eal_pci.c
>> @@ -396,6 +396,55 @@ error:
>>       return -1;
>>  }
>>
>> +int
>> +pci_refresh_device(const struct rte_pci_addr *addr)
>
> What about pci_reload_device or pci_reload_device_info? I don't mind
> too much, only the word 'refresh' reminds me other associations.

Or maybe pci_update_device ?
I added pci_add_device in my other pci patchset, so update sounds better to me.


>> +{
>> +     int fd;
>> +     struct pci_conf matches[2];
>> +     struct pci_match_conf match = {
>> +             .pc_sel = {
>> +                     .pc_domain = addr->domain,
>> +                     .pc_bus = addr->bus,
>> +                     .pc_dev = addr->devid,
>> +                     .pc_func = addr->function,
>> +             },
>> +     };
>> +     struct pci_conf_io conf_io = {
>> +             .pat_buf_len = 0,
>> +             .num_patterns = 1,
>> +             .patterns = { &match },
>> +             .match_buf_len = sizeof(matches),
>> +             .matches = &matches[0],
>> +     };
>> +
>> +     fd = open("/dev/pci", O_RDONLY);
>
> Just courious who provides this special file... is a DPDK-specific
> thing? I haven't noticed it anywhere in Linux.

I don't know, just took the bsd pci code and plugged myself in it.
So for me this is a special bsd device.

This is mainly copy/paste.
Look at rte_eal_pci_scan() from lib/librte_eal/bsdapp/eal/eal_pci.c.

>
>> +     if (fd < 0) {
>> +             RTE_LOG(ERR, EAL, "%s(): error opening /dev/pci\n", __func__);
>> +             goto error;
>
> If you write:
>                 return -1;
>
> then you can...
>
>> +     }
>> +
>> +     if (ioctl(fd, PCIOCGETCONF, &conf_io) < 0) {
>> +             RTE_LOG(ERR, EAL, "%s(): error with ioctl on /dev/pci: %s\n",
>> +                             __func__, strerror(errno));
>> +             goto error;
>> +     }
>> +
>> +     if (conf_io.num_matches != 1)
>> +             goto error;
>> +
>> +     if (pci_scan_one(fd, &matches[0]) < 0)
>> +             goto error;
>> +
>> +     close(fd);
>> +
>> +     return 0;
>> +
>> +error:
>
> ...remove this if:
>
>> +     if (fd >= 0)
>> +             close(fd);
>
> Or, do you consider it more stable in the orignal way?

Well, as said above, this is copy/paste code.
But, anyway, when I write functions with goto statements, I prefer
having a minimal number of return statements, matter of taste.
Another way is to add two label error_close: error: but this is a bit
overkill here.


>> +     return -1;
>> +}
>> +
>>  /* Read PCI config space. */
>>  int rte_eal_pci_read_config(const struct rte_pci_device *dev,
>>                           void *buf, size_t len, off_t offset)
>> diff --git a/lib/librte_eal/common/eal_private.h b/lib/librte_eal/common/eal_private.h
>> index 072e672..ed1903f 100644
>> --- a/lib/librte_eal/common/eal_private.h
>> +++ b/lib/librte_eal/common/eal_private.h
>> @@ -155,6 +155,19 @@ struct rte_pci_driver;
>>  struct rte_pci_device;
>>
>>  /**
>> + * Refresh a pci device object by asking the kernel for the latest information.
>> + *
>> + * This function is private to EAL.
>> + *
>> + * @param addr
>> + *   The PCI Bus-Device-Function address to look for
>> + * @return
>> + *   - 0 on success.
>> + *   - negative on error.
>
> I don't know whether this is a convention in DPDK, anyway, I don't
> like to restrict errors to just negatives. You cannot write
>
> if ((err = pci_refresh_device(...)) /* < 0 */) {
>         handle_error(err);
> }
>
> as the check for < 0 is required (easy to be avoided).

It is a remnant of a lot of code in eal that tries to have 0 for
success, < 0 for errors, > 0 for special cases.


-- 
David Marchand