Re: [PATCH v2 4/4] scsi: st: Add sysfs file reset_blocked

[John Meneghini <jmeneghi@redhat.com>]

Reviewed-by: John Meneghini <jmeneghi@redhat.com>
Tested-by: John Meneghini <jmeneghi@redhat.com>

On 11/25/24 09:03, Kai Mäkisara wrote:
> If the value read from the file is 1, reads and writes from/to the
> device are blocked because the tape position may not match user's
> expectation (tape rewound after device reset).
> 
> Signed-off-by: Kai Mäkisara <Kai.Makisara@kolumbus.fi>
> ---
>   Documentation/scsi/st.rst |  5 +++++
>   drivers/scsi/st.c         | 19 +++++++++++++++++++
>   2 files changed, 24 insertions(+)
> 
> diff --git a/Documentation/scsi/st.rst b/Documentation/scsi/st.rst
> index d3b28c28d74c..2209f03faad3 100644
> --- a/Documentation/scsi/st.rst
> +++ b/Documentation/scsi/st.rst
> @@ -157,6 +157,11 @@ enabled driver and mode options. The value in the file is a bit mask where the
>   bit definitions are the same as those used with MTSETDRVBUFFER in setting the
>   options.
>   
> +Each directory contains the entry 'reset_blocked'. If this value is one,
> +reading and writing to the device is blocked after device reset. Most
> +devices rewind the tape after reset and the writes/read don't access the
> +tape position the user expects.
> +
>   A link named 'tape' is made from the SCSI device directory to the class
>   directory corresponding to the mode 0 auto-rewind device (e.g., st0).
>   
> diff --git a/drivers/scsi/st.c b/drivers/scsi/st.c
> index ad86dfbc8919..0e6a87f1f47f 100644
> --- a/drivers/scsi/st.c
> +++ b/drivers/scsi/st.c
> @@ -4697,6 +4697,24 @@ options_show(struct device *dev, struct device_attribute *attr, char *buf)
>   }
>   static DEVICE_ATTR_RO(options);
>   
> +/**
> + * reset_blocked_show - Value 1 indicates that reads, writes, etc. are blocked
> + * because a device reset has occurred and no operation positioning the tape
> + * has been issued.
> + * @dev: struct device
> + * @attr: attribute structure
> + * @buf: buffer to return formatted data in
> + */
> +static ssize_t reset_blocked_show(struct device *dev,
> +	struct device_attribute *attr, char *buf)
> +{
> +	struct st_modedef *STm = dev_get_drvdata(dev);
> +	struct scsi_tape *STp = STm->tape;
> +
> +	return sprintf(buf, "%d", STp->pos_unknown);
> +}
> +static DEVICE_ATTR_RO(reset_blocked);
> +
>   /* Support for tape stats */
>   
>   /**
> @@ -4881,6 +4899,7 @@ static struct attribute *st_dev_attrs[] = {
>   	&dev_attr_default_density.attr,
>   	&dev_attr_default_compression.attr,
>   	&dev_attr_options.attr,
> +	&dev_attr_reset_blocked.attr,
>   	NULL,
>   };
>