Re: [PATCH v3 1/7] ata: libata-sata: Factor out NCQ Priority configuration helpers

[Igor Pylypiv <ipylypiv@google.com>]

On Mon, Mar 04, 2024 at 08:34:52AM +0000, John Garry wrote:
> On 02/03/2024 20:16, Igor Pylypiv wrote:
> > Export libata NCQ Priority configuration helpers to be reused
> > for libsas managed SATA devices.
> > 
> > Signed-off-by: Igor Pylypiv <ipylypiv@google.com>
> 
> This looks ok. Some small code comments below, though.
> 
> > ---
> >   drivers/ata/libata-sata.c | 139 +++++++++++++++++++++++++++-----------
> >   include/linux/libata.h    |   4 ++
> >   2 files changed, 103 insertions(+), 40 deletions(-)
> > 
> > diff --git a/drivers/ata/libata-sata.c b/drivers/ata/libata-sata.c
> > index 0fb1934875f2..a8d5e36d5211 100644
> > --- a/drivers/ata/libata-sata.c
> > +++ b/drivers/ata/libata-sata.c
> > @@ -848,29 +848,73 @@ DEVICE_ATTR(link_power_management_policy, S_IRUGO | S_IWUSR,
> >   	    ata_scsi_lpm_show, ata_scsi_lpm_store);
> >   EXPORT_SYMBOL_GPL(dev_attr_link_power_management_policy);
> > +/**
> > + *	ata_ncq_prio_supported - Check if device supports NCQ Priority
> > + *	@ap: ATA port of the target device
> > + *	@sdev: SCSI device
> > + *
> > + *	Helper to check if device supports NCQ Priority feature,
> > + *	usable with both libsas and libata.
> > + */
> > +int ata_ncq_prio_supported(struct ata_port *ap, struct scsi_device *sdev)
> > +{
> > +	struct ata_device *dev;
> > +	unsigned long flags;
> > +	int rc;
> > +
> > +	spin_lock_irqsave(ap->lock, flags);
> > +	dev = ata_scsi_find_dev(ap, sdev);
> > +	if (!dev)
> > +		rc = -ENODEV;
> > +	else
> > +		rc = !!(dev->flags & ATA_DFLAG_NCQ_PRIO);
> > +	spin_unlock_irqrestore(ap->lock, flags);
> > +	return rc;
> > +}
> 
> I'm not the biggest fan of functions which effectively return both a boolean
> and an error code.
> 
> I like this patten more:
> 
> int ata_ncq_prio_supported(struct ata_port *ap, struct scsi_device *sdev,
> bool *supported)
> {
> 	...
> 	if (rc)
> 		return rc;
> 	*supported = true/false.
> 	return 0;
> }
> 
> No big deal, though.

Thanks for the review, John. Separating out an error code and a boolean
makes the code a bit more readable. Sent out v4 with the changes.

> 
> > +EXPORT_SYMBOL_GPL(ata_ncq_prio_supported);
> > +
> >   static ssize_t ata_ncq_prio_supported_show(struct device *device,
> >   					   struct device_attribute *attr,
> >   					   char *buf)
> >   {
> >   	struct scsi_device *sdev = to_scsi_device(device);
> >   	struct ata_port *ap = ata_shost_to_port(sdev->host);
> > +	int rc;
> > +
> > +	rc = ata_ncq_prio_supported(ap, sdev);
> > +	if (rc < 0)
> > +		return rc;
> > +
> > +	return sysfs_emit(buf, "%d\n", rc);
> > +}
> > +
> > +DEVICE_ATTR(ncq_prio_supported, S_IRUGO, ata_ncq_prio_supported_show, NULL);
> > +EXPORT_SYMBOL_GPL(dev_attr_ncq_prio_supported);
> > +
> > +/**
> > + *	ata_ncq_prio_enabled - Check if NCQ Priority is enabled
> > + *	@ap: ATA port of the target device
> > + *	@sdev: SCSI device
> > + *
> > + *	Helper to check if NCQ Priority feature is enabled,
> > + *	usable with both libsas and libata.
> 
> It's usable by anything which uses libata, really. For the moment that is
> libsas and libata.
> 
> > + */
> > +int ata_ncq_prio_enabled(struct ata_port *ap, struct scsi_device *sdev)
> > +{
> >   	struct ata_device *dev;
> > -	bool ncq_prio_supported;
> > -	int rc = 0;
> > +	unsigned long flags;
> > +	int rc;
> > -	spin_lock_irq(ap->lock);
> > +	spin_lock_irqsave(ap->lock, flags);
> >   	dev = ata_scsi_find_dev(ap, sdev);
> >   	if (!dev)
> >   		rc = -ENODEV;
> >   	else
> > -		ncq_prio_supported = dev->flags & ATA_DFLAG_NCQ_PRIO;
> > -	spin_unlock_irq(ap->lock);
> > -
> > -	return rc ? rc : sysfs_emit(buf, "%u\n", ncq_prio_supported);
> > +		rc = !!(dev->flags & ATA_DFLAG_NCQ_PRIO_ENABLED);
> > +	spin_unlock_irqrestore(ap->lock, flags);
> > +	return rc;
> >   }
> > -
> > -DEVICE_ATTR(ncq_prio_supported, S_IRUGO, ata_ncq_prio_supported_show, NULL);
> > -EXPORT_SYMBOL_GPL(dev_attr_ncq_prio_supported);
> > +EXPORT_SYMBOL_GPL(ata_ncq_prio_enabled);
> >   static ssize_t ata_ncq_prio_enable_show(struct device *device,
> >   					struct device_attribute *attr,
> > @@ -878,50 +922,45 @@ static ssize_t ata_ncq_prio_enable_show(struct device *device,
> >   {
> >   	struct scsi_device *sdev = to_scsi_device(device);
> >   	struct ata_port *ap = ata_shost_to_port(sdev->host);
> > -	struct ata_device *dev;
> > -	bool ncq_prio_enable;
> > -	int rc = 0;
> > +	int rc;
> > -	spin_lock_irq(ap->lock);
> > -	dev = ata_scsi_find_dev(ap, sdev);
> > -	if (!dev)
> > -		rc = -ENODEV;
> > -	else
> > -		ncq_prio_enable = dev->flags & ATA_DFLAG_NCQ_PRIO_ENABLED;
> > -	spin_unlock_irq(ap->lock);
> > +	rc = ata_ncq_prio_enabled(ap, sdev);
> > +	if (rc < 0)
> > +		return rc;
> > -	return rc ? rc : sysfs_emit(buf, "%u\n", ncq_prio_enable);
> > +	return sysfs_emit(buf, "%d\n", rc);
> >   }
> > -static ssize_t ata_ncq_prio_enable_store(struct device *device,
> > -					 struct device_attribute *attr,
> > -					 const char *buf, size_t len)
> > +/**
> > + *	ata_ncq_prio_enable - Enable/disable NCQ Priority
> > + *	@ap: ATA port of the target device
> > + *	@sdev: SCSI device
> > + *	@enable: true - enable NCQ Priority, false - disable NCQ Priority
> > + *
> > + *	Helper to enable/disable NCQ Priority feature, usable with both
> > + *	libsas and libata.
> > + */
> > +int ata_ncq_prio_enable(struct ata_port *ap, struct scsi_device *sdev,
> > +			bool enable)
> >   {
> > -	struct scsi_device *sdev = to_scsi_device(device);
> > -	struct ata_port *ap;
> >   	struct ata_device *dev;
> > -	long int input;
> > +	unsigned long flags;
> >   	int rc = 0;
> > -	rc = kstrtol(buf, 10, &input);
> > -	if (rc)
> > -		return rc;
> > -	if ((input < 0) || (input > 1))
> > -		return -EINVAL;
> > +	spin_lock_irqsave(ap->lock, flags);
> > -	ap = ata_shost_to_port(sdev->host);
> >   	dev = ata_scsi_find_dev(ap, sdev);
> > -	if (unlikely(!dev))
> > -		return  -ENODEV;
> > -
> > -	spin_lock_irq(ap->lock);
> > +	if (unlikely(!dev)) {
> 
> no need for unlikely() - this is not fathpath
> 
> > +		rc = -ENODEV;
> > +		goto unlock;
> > +	}
> >   	if (!(dev->flags & ATA_DFLAG_NCQ_PRIO)) {
> >   		rc = -EINVAL;
> >   		goto unlock;
>