[PATCH v10 0/2] libsas: rediscover improvements for linkrate/sas_addr

When a device attached to an expander phy experiences a linkrate change
(e.g., due to cable reconnection or negotiation), the current code in
sas_rediscover_dev() treats it as "broadcast flutter" and takes no action
if the SAS address and device type remain unchanged.

This series is based on John Garry's suggestion [1] to check the linkrate
and mark the device as gone and rediscover when flutter occurs, replacing
the previous v2 patch series that used lldd callbacks.

The previous v2 approach added lldd_dev_info_update callback which John
commented as "seem fragile and too specialized" [2]. This series adopts
a simpler approach that directly checks linkrate/sas_addr changes in
sas_rediscover_dev() and triggers rediscovery using libsas's standard
async discovery pattern.

This aligns with Jason Yan's earlier work [3] which was verified to
solve the linkrate change issue.

Additionally, per the discussion in v3 [4], the existing replace code
path also suffers from the same sysfs duplication issue:
sas_unregister_devs_sas_addr() only marks the device as gone, but the
actual sysfs cleanup happens later in sas_destruct_devices(). Calling
sas_discover_new() immediately after unregister causes sysfs_warn_dup()
errors. This series also optimizes the replace path to use the async
pattern, ensuring proper ordering for both flutter and replace cases.

Changes from v9:
- Rename sas_ex_to_dev() to sas_ex_phy_to_dev() per John's review [5],
  for consistency with sas_ex_phy_discover() and other phy-related
  helpers
- Remove the defensive NULL check for ex_dev per John's review [5], as
  no current caller passes a NULL expander device. The check was added
  in v7 based on an automated Sashiko AI review suggestion which may
  contain noise

Full changelog at [6].

[1] https://lore.kernel.org/linux-scsi/[email protected]/
[2] https://lore.kernel.org/linux-scsi/[email protected]/
[3] https://lore.kernel.org/linux-scsi/[email protected]/
[4] https://lore.kernel.org/linux-scsi/[email protected]/
[5] https://lore.kernel.org/linux-scsi/[email protected]/
[6] https://lore.kernel.org/linux-scsi/[email protected]/

Xingui Yang (2):
  scsi: libsas: Add sas_ex_phy_to_dev() helper
  scsi: libsas: Add linkrate and sas_addr change detection in rediscover

 drivers/scsi/libsas/sas_expander.c | 96 ++++++++++++++++++++++++------
 drivers/scsi/libsas/sas_internal.h |  1 +
 2 files changed, 79 insertions(+), 18 deletions(-)

-- 
2.43.0