Re: [PATCH v7 2/7] scsi: libsas: Define NCQ Priority sysfs attributes for SATA devices

[Igor Pylypiv <ipylypiv@google.com>]

On Wed, Mar 06, 2024 at 11:54:52AM +0100, Niklas Cassel wrote:
> On Tue, Mar 05, 2024 at 05:22:21PM -0800, Igor Pylypiv wrote:
> > Libata sysfs attributes cannot be used for libsas managed SATA devices
> > because the ata_port location is different for libsas.
> > 
> > Defined sysfs attributes (visible for SATA devices only):
> > - /sys/block/sda/device/ncq_prio_enable
> > - /sys/block/sda/device/ncq_prio_supported
> > 
> > The newly defined attributes will pass the correct ata_port to libata
> > helper functions.
> > 
> > Reviewed-by: John Garry <john.g.garry@oracle.com>
> > Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
> > Reviewed-by: Jason Yan <yanaijie@huawei.com>
> > Signed-off-by: Igor Pylypiv <ipylypiv@google.com>
> > ---
> >  drivers/scsi/libsas/sas_ata.c | 94 +++++++++++++++++++++++++++++++++++
> >  include/scsi/sas_ata.h        |  6 +++
> >  2 files changed, 100 insertions(+)
> > 
> > diff --git a/drivers/scsi/libsas/sas_ata.c b/drivers/scsi/libsas/sas_ata.c
> > index 12e2653846e3..04b0bd9a4e01 100644
> > --- a/drivers/scsi/libsas/sas_ata.c
> > +++ b/drivers/scsi/libsas/sas_ata.c
> > @@ -964,3 +964,97 @@ int sas_execute_ata_cmd(struct domain_device *device, u8 *fis, int force_phy_id)
> >  			       force_phy_id, &tmf_task);
> >  }
> >  EXPORT_SYMBOL_GPL(sas_execute_ata_cmd);
> > +
> > +static ssize_t sas_ncq_prio_supported_show(struct device *device,
> > +					   struct device_attribute *attr,
> > +					   char *buf)
> > +{
> > +	struct scsi_device *sdev = to_scsi_device(device);
> > +	struct domain_device *ddev = sdev_to_domain_dev(sdev);
> > +	bool supported;
> > +	int rc;
> > +
> > +	/* This attribute shall be visible for SATA devices only */
> > +	if (WARN_ON_ONCE(!dev_is_sata(ddev)))
> > +		return -EINVAL;
> 
> Like Hannes commented, I don't believe this is needed.
> 

The intention for the check is to serve as a fail-safe in case 'is_visible()'
callback gets incorrectly modified and stops hiding the sysfs attributes
for non-SATA devices.

Just want to clarify should I remove the WARN_ON_ONCE and keep the fail-safe
check or should I get rid of the check completely and trust 'is_visible()'
to always hide the sysfs attributes for non-SATA devices? 

> 
> > +
> > +	rc = ata_ncq_prio_supported(ddev->sata_dev.ap, sdev, &supported);
> > +	if (rc)
> > +		return rc;
> > +
> > +	return sysfs_emit(buf, "%d\n", supported);
> > +}
> > +
> 
> While this is a bit different depending on file, the most common way is to
> have no blank link before the DEVICE_ATTR().
>

In "[PATCH 1/3] ata: libata-sata: Factor out NCQ Priority configuration helpers"
Damien asked to keep the blank link before the DEVICE_ATTR() in libata-sata.c.

Non-prio sysfs attributes in libata-sata.c don't have blank lines
before DEVICE_ATTR() so I'm more inclined to remove the lines.

I'm fine with either of ways, just want to get a consensus and make it 
consistent for both libata-sata.c and sas_ata.c.
 
> 
> > +DEVICE_ATTR(ncq_prio_supported, S_IRUGO, sas_ncq_prio_supported_show, NULL);
> > +
> > +static ssize_t sas_ncq_prio_enable_show(struct device *device,
> > +					struct device_attribute *attr,
> > +					char *buf)
> > +{
> > +	struct scsi_device *sdev = to_scsi_device(device);
> > +	struct domain_device *ddev = sdev_to_domain_dev(sdev);
> > +	bool enabled;
> > +	int rc;
> > +
> > +	/* This attribute shall be visible for SATA devices only */
> > +	if (WARN_ON_ONCE(!dev_is_sata(ddev)))
> > +		return -EINVAL;
> > +
> > +	rc = ata_ncq_prio_enabled(ddev->sata_dev.ap, sdev, &enabled);
> > +	if (rc)
> > +		return rc;
> > +
> > +	return sysfs_emit(buf, "%d\n", enabled);
> > +}
> > +
> > +static ssize_t sas_ncq_prio_enable_store(struct device *device,
> > +					 struct device_attribute *attr,
> > +					 const char *buf, size_t len)
> > +{
> > +	struct scsi_device *sdev = to_scsi_device(device);
> > +	struct domain_device *ddev = sdev_to_domain_dev(sdev);
> > +	bool enable;
> > +	int rc;
> > +
> > +	/* This attribute shall be visible for SATA devices only */
> > +	if (WARN_ON_ONCE(!dev_is_sata(ddev)))
> > +		return -EINVAL;
> > +
> > +	rc = kstrtobool(buf, &enable);
> > +	if (rc)
> > +		return rc;
> > +
> > +	rc = ata_ncq_prio_enable(ddev->sata_dev.ap, sdev, enable);
> > +	if (rc)
> > +		return rc;
> > +
> > +	return len;
> > +}
> > +
> > +DEVICE_ATTR(ncq_prio_enable, S_IRUGO | S_IWUSR,
> > +	    sas_ncq_prio_enable_show, sas_ncq_prio_enable_store);
> > +
> > +static struct attribute *sas_ata_sdev_attrs[] = {
> > +	&dev_attr_ncq_prio_supported.attr,
> > +	&dev_attr_ncq_prio_enable.attr,
> > +	NULL
> > +};
> > +
> > +static umode_t sas_ata_attr_is_visible(struct kobject *kobj,
> > +				       struct attribute *attr, int i)
> > +{
> > +	struct device *dev = kobj_to_dev(kobj);
> > +	struct scsi_device *sdev = to_scsi_device(dev);
> > +	struct domain_device *ddev = sdev_to_domain_dev(sdev);
> > +
> > +	if (!dev_is_sata(ddev))
> > +		return 0;
> > +
> > +	return attr->mode;
> > +}
> > +
> > +const struct attribute_group sas_ata_sdev_attr_group = {
> > +	.attrs = sas_ata_sdev_attrs,
> > +	.is_visible = sas_ata_attr_is_visible,
> > +};
> > +EXPORT_SYMBOL_GPL(sas_ata_sdev_attr_group);
> > diff --git a/include/scsi/sas_ata.h b/include/scsi/sas_ata.h
> > index 2f8c719840a6..92e27e7bf088 100644
> > --- a/include/scsi/sas_ata.h
> > +++ b/include/scsi/sas_ata.h
> > @@ -39,6 +39,9 @@ int smp_ata_check_ready_type(struct ata_link *link);
> >  int sas_discover_sata(struct domain_device *dev);
> >  int sas_ata_add_dev(struct domain_device *parent, struct ex_phy *phy,
> >  		    struct domain_device *child, int phy_id);
> > +
> > +extern const struct attribute_group sas_ata_sdev_attr_group;
> > +
> >  #else
> >  
> >  static inline void sas_ata_disabled_notice(void)
> > @@ -123,6 +126,9 @@ static inline int sas_ata_add_dev(struct domain_device *parent, struct ex_phy *p
> >  	sas_ata_disabled_notice();
> >  	return -ENODEV;
> >  }
> > +
> > +#define sas_ata_sdev_attr_group ((struct attribute_group) {})
> > +
> >  #endif
> >  
> >  #endif /* _SAS_ATA_H_ */
> > -- 
> > 2.44.0.278.ge034bb2e1d-goog
> >