Re: [PATCH 03/20] lightnvm: fix capabilities for 2.0 sysfs

From: "Matias Bjørling" <mb@lightnvm.io>
To: Javier Gonzalez <javier@cnexlabs.com>
Cc: "linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-nvme@lists.infradead.org" <linux-nvme@lists.infradead.org>
Subject: Re: [PATCH 03/20] lightnvm: fix capabilities for 2.0 sysfs
Date: Thu, 22 Feb 2018 12:10:55 +0100	[thread overview]
Message-ID: <e4ac9c84-3dd5-41e3-8190-905d2a7f5d5d@lightnvm.io> (raw)
In-Reply-To: <A949EA48-27DF-4370-B213-3A4CE4E4F7D1@cnexlabs.com>

On 02/22/2018 11:25 AM, Javier Gonzalez wrote:
> 
> 
>> On 22 Feb 2018, at 10.39, Matias Bjørling <mb@lightnvm.io> wrote:
>>
>> On 02/22/2018 08:47 AM, Javier Gonzalez wrote:
>>>> On 22 Feb 2018, at 08.28, Matias Bjørling <mb@lightnvm.io> wrote:
>>>>
>>>>> On 02/21/2018 10:26 AM, Javier González wrote:
>>>>> Both 1.2 and 2.0 specs define a field for media and controller
>>>>> capabilities. Also, 1.2 defines a separate field dedicated to device
>>>>> capabilities.
>>>>> In 2.0 sysfs, this values have been mixed. Revert them to the right
>>>>> value.
>>>>> Signed-off-by: Javier González <javier@cnexlabs.com>
>>>>> ---
>>>>>   drivers/nvme/host/lightnvm.c | 18 +++++++++---------
>>>>>   1 file changed, 9 insertions(+), 9 deletions(-)
>>>>> diff --git a/drivers/nvme/host/lightnvm.c b/drivers/nvme/host/lightnvm.c
>>>>> index 969bb874850c..598abba66f52 100644
>>>>> --- a/drivers/nvme/host/lightnvm.c
>>>>> +++ b/drivers/nvme/host/lightnvm.c
>>>>> @@ -914,8 +914,8 @@ static ssize_t nvm_dev_attr_show(struct device *dev,
>>>>>         if (strcmp(attr->name, "version") == 0) {
>>>>>           return scnprintf(page, PAGE_SIZE, "%u\n", dev_geo->ver_id);
>>>>> -    } else if (strcmp(attr->name, "capabilities") == 0) {
>>>>> -        return scnprintf(page, PAGE_SIZE, "%u\n", dev_geo->c.cap);
>>>>> +    } else if (strcmp(attr->name, "media_capabilities") == 0) {
>>>>> +        return scnprintf(page, PAGE_SIZE, "%u\n", dev_geo->c.mccap);
>>>>>       } else if (strcmp(attr->name, "read_typ") == 0) {
>>>>>           return scnprintf(page, PAGE_SIZE, "%u\n", dev_geo->c.trdt);
>>>>>       } else if (strcmp(attr->name, "read_max") == 0) {
>>>>> @@ -993,8 +993,8 @@ static ssize_t nvm_dev_attr_show_12(struct device *dev,
>>>>>           return scnprintf(page, PAGE_SIZE, "%u\n", dev_geo->c.tbem);
>>>>>       } else if (strcmp(attr->name, "multiplane_modes") == 0) {
>>>>>           return scnprintf(page, PAGE_SIZE, "0x%08x\n", dev_geo->c.mpos);
>>>>> -    } else if (strcmp(attr->name, "media_capabilities") == 0) {
>>>>> -        return scnprintf(page, PAGE_SIZE, "0x%08x\n", dev_geo->c.mccap);
>>>>> +    } else if (strcmp(attr->name, "capabilities") == 0) {
>>>>> +        return scnprintf(page, PAGE_SIZE, "0x%08x\n", dev_geo->c.cap);
>>>>>       } else if (strcmp(attr->name, "max_phys_secs") == 0) {
>>>>>           return scnprintf(page, PAGE_SIZE, "%u\n", NVM_MAX_VLBA);
>>>>>       } else {
>>>>> @@ -1055,7 +1055,7 @@ static ssize_t nvm_dev_attr_show_20(struct device *dev,
>>>>>     /* general attributes */
>>>>>   static NVM_DEV_ATTR_RO(version);
>>>>> -static NVM_DEV_ATTR_RO(capabilities);
>>>>> +static NVM_DEV_ATTR_RO(media_capabilities);
>>>>>     static NVM_DEV_ATTR_RO(read_typ);
>>>>>   static NVM_DEV_ATTR_RO(read_max);
>>>>> @@ -1080,12 +1080,12 @@ static NVM_DEV_ATTR_12_RO(prog_max);
>>>>>   static NVM_DEV_ATTR_12_RO(erase_typ);
>>>>>   static NVM_DEV_ATTR_12_RO(erase_max);
>>>>>   static NVM_DEV_ATTR_12_RO(multiplane_modes);
>>>>> -static NVM_DEV_ATTR_12_RO(media_capabilities);
>>>>> +static NVM_DEV_ATTR_12_RO(capabilities);
>>>>>   static NVM_DEV_ATTR_12_RO(max_phys_secs);
>>>>>     static struct attribute *nvm_dev_attrs_12[] = {
>>>>>       &dev_attr_version.attr,
>>>>> -    &dev_attr_capabilities.attr,
>>>>> +    &dev_attr_media_capabilities.attr,
>>>>>         &dev_attr_vendor_opcode.attr,
>>>>>       &dev_attr_device_mode.attr,
>>>>> @@ -1108,7 +1108,7 @@ static struct attribute *nvm_dev_attrs_12[] = {
>>>>>       &dev_attr_erase_typ.attr,
>>>>>       &dev_attr_erase_max.attr,
>>>>>       &dev_attr_multiplane_modes.attr,
>>>>> -    &dev_attr_media_capabilities.attr,
>>>>> +    &dev_attr_capabilities.attr,
>>>>>       &dev_attr_max_phys_secs.attr,
>>>>>         NULL,
>>>>> @@ -1134,7 +1134,7 @@ static NVM_DEV_ATTR_20_RO(reset_max);
>>>>>     static struct attribute *nvm_dev_attrs_20[] = {
>>>>>       &dev_attr_version.attr,
>>>>> -    &dev_attr_capabilities.attr,
>>>>> +    &dev_attr_media_capabilities.attr,
>>>>>         &dev_attr_groups.attr,
>>>>>       &dev_attr_punits.attr,
>>>>
>>>> With the mccap changes, it should make sense to keep the capabilities
>>>> as is.
>>> The change adds mccap, but sysfs points to cap, which is wrong. This
>>> patch is needed. Otherwise, we change the name of mccap to cap, which
>>> is _very_ confusing to people familiar to both specs. We can change
>>> the name of mccap to cap in a future spec revision.
>>> Javier
>>
>> Think of the sysfs capabilities as an abstract value that defines generic capabilities. It is not directly tied to either 1.2 or 2.0.
> 
> I’m thinking about the user looking at sysfs and at the spec at the same time - I myself get confused when names don’t match.
> 
> Anyway, I’ll keep it the way it was and add a comment for clarification. Would that work for you?
> 

That works. One may also wait until it is going to be used, e.g., when 
vector copy is implemented. Then it's natural to revisit.