Re: [PATCH v2 2/5] ata: libata-scsi: convert dev->sdev to per-LUN array

[Hannes Reinecke <hare@suse.de>]

On 4/20/26 14:23, Phil Pemberton wrote:
> Multi-LUN ATAPI devices (PD/CD combos, CD changers) share a single
> ata_device but expose multiple scsi_devices.  The previous single
> dev->sdev pointer could only track one LUN, making all other LUNs
> invisible to code that operates on sdevs: port detach, suspend/resume,
> ACPI uevent, ZPODD, media change notification, and EH teardown.
> 
> Replace the scalar struct scsi_device *sdev with a fixed-size array
> dev->sdev[ATAPI_MAX_LUN] indexed by LUN number, where ATAPI_MAX_LUN
> is 8 (the SCSI-2 ceiling, LUN values 0..7).
> 
> Key changes per call site:
>    - ata_scsi_dev_config:  assign sdev to dev->sdev[sdev->lun]
>    - ata_scsi_sdev_destroy: clear dev->sdev[sdev->lun]; only trigger
>      ATA-level detach when LUN 0 is destroyed, since removing a higher
>      LUN should not tear down the underlying ATA device
>    - ata_port_detach:  iterate all LUN slots (high→low)
>    - ata_scsi_offline_dev:  iterate all LUN slots
>    - ata_scsi_remove_dev:  snapshot and remove all LUN slots, then
>      scsi_remove_device each one outside the lock
>    - ata_scsi_media_change_notify:  send event to all populated LUNs
>    - ata_scsi_dev_rescan:  resume and rescan each populated LUN
>    - ACPI, ZPODD, ofnode, door-lock:  use dev->sdev[0] (LUN 0 remains
>      canonical for ATA-level operations)
>    - ata_scsi_scan_host:  uses dev->sdev[0] for the existing LUN-0
>      add/retry path
> 
> For single-LUN devices (the vast majority), only dev->sdev[0] is ever
> populated and the additional slots remain NULL.
> 
> Signed-off-by: Phil Pemberton <philpem@philpem.me.uk>
> ---
>   drivers/ata/libata-acpi.c  |   4 +-
>   drivers/ata/libata-core.c  |  10 ++-
>   drivers/ata/libata-scsi.c  | 146 ++++++++++++++++++-------------------
>   drivers/ata/libata-zpodd.c |   6 +-
>   include/linux/libata.h     |   2 +-
>   5 files changed, 86 insertions(+), 82 deletions(-)
> 
Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
hare@suse.de                                +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
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