linux-kernel - [PATCH v2 0/3] scsi: add runtime PM workaround for SD cardreaders

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Date:   Tue, 12 Jan 2021 10:33:26 +0100
From:   Martin Kepplinger <martin.kepplinger@...i.sm>
To:     jejb@...ux.ibm.com, martin.petersen@...cle.com,
        stern@...land.harvard.edu, bvanassche@....org
Cc:     linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
        Martin Kepplinger <martin.kepplinger@...i.sm>
Subject: [PATCH v2 0/3] scsi: add runtime PM workaround for SD cardreaders

revision history
----------------
v2:
 * move module parameter to sd
 * add Documentation

v1:
https://lore.kernel.org/linux-scsi/20210111152029.28426-1-martin.kepplinger@puri.sm/T/#t

hi,

In short: there are SD cardreaders that send MEDIA_CHANGED on
runtime resume. We cannot use runtime PM with these devices as
I/O basically always fails. I'd like to discuss a way to fix this
or at least allow users to work around this problem:

For the full background, the discussion started in June 2020 here:
https://lore.kernel.org/linux-scsi/20200623111018.31954-1-martin.kepplinger@puri.sm/

and I sent the first of these patches in August, as a reference:
https://lore.kernel.org/linux-scsi/20200824190400.12339-1-martin.kepplinger@puri.sm/
so this is where I'm following up on.

I'm not sure whether maintaining an in-kernel quirk for specific devices
makes sense so here I suggest adding a userspace knob. This way there's at
least a chance to use runtime PM for sd cardreaders that send MEDIA_CHANGED.

I'd appreciate any feedback.

Martin Kepplinger (3):
  scsi: add expecting_media_change flag to error path
  scsi: sd: add ignore_resume_medium_changed disk setting
  scsi: sd: Documentation: describe ignore_resume_medium_changed

 Documentation/scsi/sd-parameters.rst | 14 ++++++++
 drivers/scsi/scsi_error.c            | 36 +++++++++++++++++---
 drivers/scsi/sd.c                    | 50 +++++++++++++++++++++++++++-
 drivers/scsi/sd.h                    |  1 +
 include/scsi/scsi_device.h           |  1 +
 5 files changed, 96 insertions(+), 6 deletions(-)

-- 
2.20.1