Re: [ndctl PATCH v5 1/6] libndctl: Refactor out add_dimm() to handle NFIT specific init

[Vaibhav Jain <vaibhav@linux.ibm.com>]

Hi Vishal,

Thanks for reviewing this patch. My responses below:

"Verma, Vishal L" <vishal.l.verma@intel.com> writes:

> On Sat, 2020-05-30 at 03:35 +0530, Vaibhav Jain wrote:
>> Presently add_dimm() only probes dimms that support NFIT/ACPI. Hence
>> this patch refactors this functionality into two functions namely
>> add_dimm() and add_nfit_dimm(). Function add_dimm() performs
>> allocation and common 'struct ndctl_dimm' initialization and depending
>> on whether the dimm-bus supports NIFT, calls add_nfit_dimm(). Once
>> the probe is completed based on the value of 'ndctl_dimm.cmd_family'
>> appropriate dimm-ops are assigned to the dimm.
>> 
>> In case dimm-bus is of unknown type or doesn't support NFIT the
>> initialization still continues, with no dimm-ops assigned to the
>> 'struct ndctl_dimm' there-by limiting the functionality available.
>> 
>> This patch shouldn't introduce any behavioral change.
>> 
>> Signed-off-by: Vaibhav Jain <vaibhav@linux.ibm.com>
>> ---
>> Changelog:
>> 
>> v4..v5:
>> * None
>> 
>> v3..v4:
>> * None
>> 
>> v2..v3:
>> * None
>> 
>> v1..v2:
>> * None
>> ---
>>  ndctl/lib/libndctl.c | 193 +++++++++++++++++++++++++-----------------
>> -
>>  1 file changed, 112 insertions(+), 81 deletions(-)
>
> Hi Vaibhav,
>
> This mostly looks good, one minor nit below.
>
>> 
>> diff --git a/ndctl/lib/libndctl.c b/ndctl/lib/libndctl.c
>> index ee737cbbfe3e..d76dbf7e17de 100644
>> --- a/ndctl/lib/libndctl.c
>> +++ b/ndctl/lib/libndctl.c
>> @@ -1441,82 +1441,15 @@ static int ndctl_bind(struct ndctl_ctx *ctx, struct kmod_module *module,
>>  static int ndctl_unbind(struct ndctl_ctx *ctx, const char *devpath);
>>  static struct kmod_module *to_module(struct ndctl_ctx *ctx, const char *alias);
>>  
>> -static void *add_dimm(void *parent, int id, const char *dimm_base)
>> +static int add_nfit_dimm(struct ndctl_dimm *dimm, const char *dimm_base)
>>  {
>> -	int formats, i;
>> -	struct ndctl_dimm *dimm;
>> +	int i, rc = -1;
>>  	char buf[SYSFS_ATTR_SIZE];
>> -	struct ndctl_bus *bus = parent;
>> -	struct ndctl_ctx *ctx = bus->ctx;
>> +	struct ndctl_ctx *ctx = dimm->bus->ctx;
>>  	char *path = calloc(1, strlen(dimm_base) + 100);
>>  
>>  	if (!path)
>
> <snip>
>
>> +		return -1;
>
> You should generally avoid returning a plain '-1'. This really wants to
> return an -ENOMEM.
If calloc fails, variable 'errno' will already be set to ENOMEM. Hence
didn't explicitly return -ENOMEM. But fair suggestion will update
this in v6.

>>  
>>  	/*
>>  	 * 'unique_id' may not be available on older kernels, so don't
>> @@ -1582,24 +1515,15 @@ static void *add_dimm(void *parent, int id, const char *dimm_base)
>>  	sprintf(path, "%s/nfit/family", dimm_base);
>>  	if (sysfs_read_attr(ctx, path, buf) == 0)
>>  		dimm->cmd_family = strtoul(buf, NULL, 0);
>> -	if (dimm->cmd_family == NVDIMM_FAMILY_INTEL)
>> -		dimm->ops = intel_dimm_ops;
>> -	if (dimm->cmd_family == NVDIMM_FAMILY_HPE1)
>> -		dimm->ops = hpe1_dimm_ops;
>> -	if (dimm->cmd_family == NVDIMM_FAMILY_MSFT)
>> -		dimm->ops = msft_dimm_ops;
>> -	if (dimm->cmd_family == NVDIMM_FAMILY_HYPERV)
>> -		dimm->ops = hyperv_dimm_ops;
>>  
>>  	sprintf(path, "%s/nfit/dsm_mask", dimm_base);
>>  	if (sysfs_read_attr(ctx, path, buf) == 0)
>>  		dimm->nfit_dsm_mask = strtoul(buf, NULL, 0);
>>  
>> -	dimm->formats = formats;
>>  	sprintf(path, "%s/nfit/format", dimm_base);
>>  	if (sysfs_read_attr(ctx, path, buf) == 0)
>>  		dimm->format[0] = strtoul(buf, NULL, 0);
>> -	for (i = 1; i < formats; i++) {
>> +	for (i = 1; i < dimm->formats; i++) {
>>  		sprintf(path, "%s/nfit/format%d", dimm_base, i);
>>  		if (sysfs_read_attr(ctx, path, buf) == 0)
>>  			dimm->format[i] = strtoul(buf, NULL, 0);
>> @@ -1610,7 +1534,114 @@ static void *add_dimm(void *parent, int id, const char *dimm_base)
>
> <snip>
>
>>   out:
>> +	if (rc) {
>> +		err(ctx, "Unable to probe dimm:%d. Err:%d\n", id, rc);
>
> Returning -1 being awkward is especially true when it might end up
> getting printed as part of an error message like this. Indeed, you    
> shouldn't even print 'rc' as a number, which then needs to get looked up
> - use strerror to turn it into a string.
>
> Additionally, "dimm:<number>" is pretty nonstandard in ndctl, we
> normally use the 'devname' for error messages. How about something
> like:
>
> 	err(ctx, "%s: probe failed: %s\n", ndctl_dimm_get_devname(dimm),
> 		strerror(-rc));
>
Fair suggestion. Will update this in v6. 
>> +		goto err_read;
>> +	}
>> +
>>  	list_add(&bus->dimms, &dimm->list);
>>  	free(path);
>>  

-- 
Cheers
~ Vaibhav
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