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

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Message-ID: <616ad3c9-b10c-0439-2d63-5e9e25abce84@lightnvm.io>
Date:   Thu, 22 Feb 2018 10:39:08 +0100
From:   Matias Bjørling <mb@...htnvm.io>
To:     Javier Gonzalez <javier@...xlabs.com>
Cc:     "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-nvme@...ts.infradead.org" <linux-nvme@...ts.infradead.org>
Subject: Re: [PATCH 03/20] lightnvm: fix capabilities for 2.0 sysfs

On 02/22/2018 08:47 AM, Javier Gonzalez wrote:
>> On 22 Feb 2018, at 08.28, Matias Bjørling <mb@...htnvm.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@...xlabs.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.