[PATCH libdrm 05/10] xf86drm: introduce a get_real_pci_path() helper

[Eric Engestrom]

On Thursday, 2018-06-28 11:21:26 +0100, Eric Engestrom wrote:
> On Monday, 2018-06-25 17:39:14 +0000, Emil Velikov wrote:
> > From: Emil Velikov <emil.velikov at collabora.com>
> > 
> > Introduce a helper which gets the real sysfs path for the given pci
> > device.
> > 
> > In other words, instead opening the /sys/dev/char/*/device symlink, we
> > opt for the actual /sys/devices/pci*/*/
> > 
> > It folds three (nearly identical) snprintf's and paves the way of adding
> > extra devices (see next patch) a piece of pie.
> > 
> > Signed-off-by: Emil Velikov <emil.velikov at collabora.com>
> > ---
> >  xf86drm.c | 62 ++++++++++++++++++++++++++++++++++++++++++++-----------
> >  1 file changed, 50 insertions(+), 12 deletions(-)
> > 
> > diff --git a/xf86drm.c b/xf86drm.c
> > index d4810740..8ccd528f 100644
> > --- a/xf86drm.c
> > +++ b/xf86drm.c
> > @@ -2992,16 +2992,37 @@ static int drmParseSubsystemType(int maj, int min)
> >  #endif
> >  }
> >  
> > +static char *
> > +get_real_pci_path(int maj, int min)
> > +{
> > +    char path[PATH_MAX + 1];
> > +    char *real_path = malloc(PATH_MAX);
> 
> Why not allocate this on the stack and pass it in?
> It would avoid the error handling you had to add in this patch :)

Sorry, I forgot to add: with that amend, the series is
Reviewed-by: Eric Engestrom <eric at engestrom.ch>

> 
> > +
> > +    if (!real_path)
> > +        return NULL;
> > +
> > +    snprintf(path, sizeof(path), "/sys/dev/char/%d:%d/device", maj, min);
> > +    if (!realpath(path, real_path)) {
> > +        free(real_path);
> > +        return NULL;
> > +    }
> > +
> > +    return real_path;
> > +}
> > +
> >  static int drmParsePciBusInfo(int maj, int min, drmPciBusInfoPtr info)
> >  {
> >  #ifdef __linux__
> >      unsigned int domain, bus, dev, func;
> > -    char path[PATH_MAX + 1], *value;
> > +    char *real_path, *value;
> >      int num;
> >  
> > -    snprintf(path, sizeof(path), "/sys/dev/char/%d:%d/device", maj, min);
> > +    real_path = get_real_pci_path(maj, min);
> > +    if (!real_path)
> > +        return -ENOENT;
> >  
> > -    value = sysfs_uevent_get(path, "PCI_SLOT_NAME");
> > +    value = sysfs_uevent_get(real_path, "PCI_SLOT_NAME");
> > +    free(real_path);
> >      if (!value)
> >          return -ENOENT;
> >  
> > @@ -3114,24 +3135,32 @@ static int parse_separate_sysfs_files(int maj, int min,
> >        "subsystem_vendor",
> >        "subsystem_device",
> >      };
> > -    char path[PATH_MAX + 1];
> > +    char path[PATH_MAX + 1], *real_path;
> >      unsigned int data[ARRAY_SIZE(attrs)];
> >      FILE *fp;
> >      int ret;
> >  
> > +    real_path = get_real_pci_path(maj, min);
> > +    if (!real_path)
> > +        return -ENOENT;
> > +
> >      for (unsigned i = ignore_revision ? 1 : 0; i < ARRAY_SIZE(attrs); i++) {
> > -        snprintf(path, PATH_MAX, "/sys/dev/char/%d:%d/device/%s", maj, min,
> > -                 attrs[i]);
> > +        snprintf(path, PATH_MAX, "%s/%s", real_path, attrs[i]);
> >          fp = fopen(path, "r");
> > -        if (!fp)
> > +        if (!fp) {
> > +            free(real_path);
> >              return -errno;
> > +        }
> >  
> >          ret = fscanf(fp, "%x", &data[i]);
> >          fclose(fp);
> > -        if (ret != 1)
> > +        if (ret != 1) {
> > +            free(real_path);
> >              return -errno;
> > +        }
> >  
> >      }
> > +    free(real_path);
> >  
> >      device->revision_id = ignore_revision ? 0xff : data[0] & 0xff;
> >      device->vendor_id = data[1] & 0xffff;
> > @@ -3145,19 +3174,28 @@ static int parse_separate_sysfs_files(int maj, int min,
> >  static int parse_config_sysfs_file(int maj, int min,
> >                                     drmPciDeviceInfoPtr device)
> >  {
> > -    char path[PATH_MAX + 1];
> > +    char path[PATH_MAX + 1], *real_path;
> >      unsigned char config[64];
> >      int fd, ret;
> >  
> > -    snprintf(path, PATH_MAX, "/sys/dev/char/%d:%d/device/config", maj, min);
> > +    real_path = get_real_pci_path(maj, min);
> > +    if (!real_path)
> > +        return -ENOENT;
> > +
> > +    snprintf(path, PATH_MAX, "%s/config", real_path);
> >      fd = open(path, O_RDONLY);
> > -    if (fd < 0)
> > +    if (fd < 0) {
> > +        free(real_path);
> >          return -errno;
> > +    }
> >  
> >      ret = read(fd, config, sizeof(config));
> >      close(fd);
> > -    if (ret < 0)
> > +    if (ret < 0) {
> > +        free(real_path);
> >          return -errno;
> > +    }
> > +    free(real_path);
> >  
> >      device->vendor_id = config[0] | (config[1] << 8);
> >      device->device_id = config[2] | (config[3] << 8);
> > -- 
> > 2.18.0
> > 
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