linux-kernel - Re: [RFC PATCH v1 1/2] block: bsg: resume scsi device before accessing

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Date:   Wed, 27 Jan 2021 16:53:52 +0800
From:   Can Guo <cang@...eaurora.org>
To:     Avri Altman <Avri.Altman@....com>
Cc:     Asutosh Das <asutoshd@...eaurora.org>, martin.petersen@...cle.com,
        linux-scsi@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        stern@...land.harvard.edu,
        "Bao D . Nguyen" <nguyenb@...eaurora.org>,
        FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>,
        Jens Axboe <axboe@...nel.dk>,
        "open list:BLOCK LAYER" <linux-block@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH v1 1/2] block: bsg: resume scsi device before
 accessing

On 2021-01-27 15:59, Can Guo wrote:
> On 2021-01-27 15:09, Avri Altman wrote:
>>> 
>>> Resumes the scsi device before accessing it.
>>> 
>>> Change-Id: I2929af60f2a92c89704a582fcdb285d35b429fde
>>> Signed-off-by: Asutosh Das <asutoshd@...eaurora.org>
>>> Signed-off-by: Can Guo <cang@...eaurora.org>
>>> Signed-off-by: Bao D. Nguyen <nguyenb@...eaurora.org>
>> Following this patch, is it possible to revert commit 74e5e468b664d?
>> 
> 
> No, but this is a good finding... This change assumes
> that the queue->queue_data is a scsi_device, which is
> why we call scsi_auto_pm_get(). But for ufs_bsg's case,
> queue->queue_data is a device...
> 

If we call pm_runtime_get/put_sync(bcd->class_dev->parent) in
bsg_get/put_device(), commit 74e5e468b664d can be reverted.
This is just a rough idea.

> Thanks,
> Can Guo.
> 
>> Thanks,
>> Avri