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Subject: Re: [PATCH] scsi: ufs: make sure scan sequence for multiple hosts
To:     Chanho Park <chanho61.park@samsung.com>, jejb@linux.ibm.com,
        martin.petersen@oracle.com
Cc:     alim.akhtar@samsung.com, avri.altman@wdc.com,
        linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org
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From:   Bart Van Assche <bvanassche@acm.org>
Message-ID: <6e204521-74e4-cc6c-27e7-3a290c492793@acm.org>
Date:   Fri, 23 Oct 2020 08:27:10 -0700
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On 10/21/20 9:59 PM, Chanho Park wrote:
>> Please use udev or systemd instead of adding code in the UFS driver that
>> is
>> not necessary when udev or systemd is used.
>>
> 
> What I mentioned was how it can be handled when we mount rootfs directly from kernel.
> 
> 1) kernel -> initramfs (mount root) -> systemd
> 2) kernel (mount root) -> systemd
>   -> In this case, we normally use root=/dev/sda1 from kernel commandline to mount the rootfs.
> 
> Like fstab can support legacy node mount, ufs driver also needs to provide
> an option for using the permanent legacy node. If you're really worry about > adding a new codes for all UFS driver, we can put this as controller specific> or optional feature.

The only code that should occur in the UFS driver is code that is specific
to UFS devices. Since the functionality in this patch is not UFS specific,
it should be added elsewhere.

Additionally, since this functionality can be implemented easily in user
space, I think it should be implemented in user space instead of in the
kernel. Even when not using systemd or udev, it is easy to implement a loop
that waits until a certain LUN or WWID appears.

Bart.