On 07/10/2017 07:27 AM, Bart Van Assche wrote:
> On Sat, 2017-07-08 at 02:52 -0500, Mike Christie wrote:
>> Userspace tools like targetcli are not able to dynamically detect if a
>> tcmu device supports kernel features ALUA or PGRs. In some kernels it
>> can create ALUA groups, but writing/reading ALUA files can lead to
>> nice error codes but also crashes and hangs.
>>
>> This patch, made over Nicks's for next branch, adds a device configfs
>> attribute to report the kernel features the device supports, so tools
>> can check that before attempting to activate some of these features
>> that were partially supported in older kernels.
>>
>> It can also be used for future feautes like possibly inquiry suppport
>> if we do end up moving that to the kernel so we can properly report
>> port info.
>>
>> [ ... ]
>> +static ssize_t tcmu_features_show(struct config_item *item, char *page)
>> +{
>> + struct se_dev_attrib *da = container_of(to_config_group(item),
>> + struct se_dev_attrib, da_group);
>> + struct tcmu_dev *udev = TCMU_DEV(da->da_dev);
>> +
>> + return snprintf(page, PAGE_SIZE, "0x%llx\n", udev->features);
>> +}
>> +CONFIGFS_ATTR_RO(tcmu_, features);
>>
>> [ ... ]
>>
>> diff --git a/include/uapi/linux/target_core_user.h b/include/uapi/linux/target_core_user.h
>> index 24a1c4e..03de6e9 100644
>> --- a/include/uapi/linux/target_core_user.h
>> +++ b/include/uapi/linux/target_core_user.h
>> @@ -154,4 +154,7 @@ enum tcmu_genl_attr {
>> };
>> #define TCMU_ATTR_MAX (__TCMU_ATTR_MAX - 1)
>>
>> +#define TCMU_KERN_ALUA (1ULL << 0)
>> +#define TCMU_KERN_PGR (1ULL << 1)
>
>
> Hello Mike,
>
> Wouldn't it be more convenient for shell scripts if the state of these flags
> would be exported through two configfs attributes instead of a single bitfield?
> Wouldn't that be more consistent with other sysfs/configfs drivers that export
> boolean values?
>
For scripts I think it would be easier. I will send a patch on top of
these to fix it up.
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