On 03/05/2018 09:43 AM, Erik Skultety wrote:
> When commit 3545cbef moved the sysfs attribute reading logic from
> _udev.c module to virmdev.c, it had to replace our udev read wrappers
> with the ones available from virfile.c. The problem is that the original
> logic worked correctly with udev read wrappers which don't return an
> error code for a missing attribute, virfile.c readers however - not so
> much. Therefore add another parameter to the macro, so we can again
> accept the fact that optional attributes may be missing.
>
> Signed-off-by: Erik Skultety <eskul...@redhat.com>
> ---
> src/util/virmdev.c | 17 +++++++++++------
> 1 file changed, 11 insertions(+), 6 deletions(-)
>
The virFileReadValue* API's return -2 for non existing file, so instead
of messing with errno, you should be able to
rc = cb();
if (rc == -2 && optional)
rc = 0;
if (rc < 0)
goto cleanup;
As it seems to be the more common way to use the functions.
John
> diff --git a/src/util/virmdev.c b/src/util/virmdev.c
> index 124933506..688f2efb5 100644
> --- a/src/util/virmdev.c
> +++ b/src/util/virmdev.c
> @@ -505,10 +505,13 @@ virMediatedDeviceTypeReadAttrs(const char *sysfspath,
> int ret = -1;
> virMediatedDeviceTypePtr tmp = NULL;
>
> -#define MDEV_GET_SYSFS_ATTR(attr, dst, cb) \
> +#define MDEV_GET_SYSFS_ATTR(attr, dst, cb, optional) \
> do { \
> - if (cb(dst, "%s/%s", sysfspath, attr) < 0) \
> - goto cleanup; \
> + errno = 0; \
> + if (cb(dst, "%s/%s", sysfspath, attr) < 0) { \
> + if (errno != ENOENT || !optional) \
> + goto cleanup; \
> + } \
> } while (0)
>
> if (VIR_ALLOC(tmp) < 0)
> @@ -517,10 +520,12 @@ virMediatedDeviceTypeReadAttrs(const char *sysfspath,
> if (VIR_STRDUP(tmp->id, last_component(sysfspath)) < 0)
> goto cleanup;
>
> - MDEV_GET_SYSFS_ATTR("name", &tmp->name, virFileReadValueString);
> - MDEV_GET_SYSFS_ATTR("device_api", &tmp->device_api,
> virFileReadValueString);
> + /* @name sysfs attribute is optional, so getting ENOENT is fine */
> + MDEV_GET_SYSFS_ATTR("name", &tmp->name, virFileReadValueString, true);
> + MDEV_GET_SYSFS_ATTR("device_api", &tmp->device_api,
> + virFileReadValueString, false);
> MDEV_GET_SYSFS_ATTR("available_instances", &tmp->available_instances,
> - virFileReadValueUint);
> + virFileReadValueUint, false);
>
> #undef MDEV_GET_SYSFS_ATTR
>
>
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