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

[Jan Viktorin]

On Wed, 10 Feb 2016 13:00:50 +0100
David Marchand <david.marchand at 6wind.com> wrote:

> 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.
> 

OK.

> 
> >> +{
> >> +     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.

BSD... I didn't notice. That's the answer.

> 
> >  
> >> +     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.

All of them are OK. As for me, I prefer to not hide simple returns.

> 
> 
> >> +     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.
> 

OK, makes sense.

> 



-- 
   Jan Viktorin                  E-mail: Viktorin at RehiveTech.com
   System Architect              Web:    www.RehiveTech.com
   RehiveTech
   Brno, Czech Republic