Re: [v4 04/11] scsi: Add durable_name for dev_printk

[Andy Shevchenko <andy.shevchenko@gmail.com>]

On Fri, Jul 24, 2020 at 8:19 PM Tony Asleson <tasleson@redhat.com> wrote:
>
> Add the needed functions to fill out the durable_name function
> call back for scsi based storage devices.  This allows calls
> into dev_printk for scsi devices to have a persistent id
> associated with them.

...

> +int scsi_durable_name(struct scsi_device *sdev, char *buf, size_t len)
> +{
> +       int vpd_len = 0;

What is the purpose of the assignment?

> +       vpd_len = scsi_vpd_lun_id(sdev, buf, len);
> +       if (vpd_len > 0 && vpd_len < len)
> +               vpd_len++;
> +       else
> +               vpd_len = 0;
> +
> +       return vpd_len;

int vpd_len;

vpd_len = ...(...);
if (vpd_len ...)
  return vpd_len + 1;
return 0;

> +}

...

>  };
>
> +

One blank line is enough.

> +int dev_to_scsi_durable_name(const struct device *dev, char *buf, size_t len)
> +{
> +       struct scsi_device *sd_dev = NULL;

Redundant assignment.

> +       // When we go through dev_printk in the scsi layer, dev is embedded
> +       // in a struct scsi_device.  When we go through the block layer,
> +       // dev is embedded in struct genhd, thus we need different paths to
> +       // retrieve the struct scsi_device to call scsi_durable_name.
> +       if (dev->type == &scsi_dev_type) {
> +               sd_dev = to_scsi_device(dev);

This...

> +       } else if (dev->parent && dev->parent->type == &scsi_dev_type) {
> +               sd_dev = to_scsi_device(dev->parent);

...and this along with pieces in scsi_bus_uevent(), scsi_bus_match()
are candidates for a good helper (perhaps with utilization of
scsi_is_sdev_device(), but maybe not necessary).

static struct scsi_device *dev_to_scsi_device(struct device *dev)
{
  return dev->type == &scsi_dev_type ? to_scsi_device(dev) : NULL;
}

sdev = dev_to_scsi_device(dev);
if (!sdev)
  sdev = dev_to_scsi_device(dev->parent);
if (!sdev)
  return 0;

And when introducing a helper change users at the same time.

> +       } else {
> +               // We have a pointer to something else, bail
> +               return 0;
> +       }
> +
> +       return scsi_durable_name(sd_dev, buf, len);
> +}

-- 
With Best Regards,
Andy Shevchenko