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Subject: RE: [RFC PATCH v2 3/5] scsi: ufs: Introduce HPB module
Reply-To: daejun7.park@samsung.com
From:   Daejun Park <daejun7.park@samsung.com>
To:     Avri Altman <Avri.Altman@wdc.com>,
        Daejun Park <daejun7.park@samsung.com>,
        ALIM AKHTAR <alim.akhtar@samsung.com>,
        "jejb@linux.ibm.com" <jejb@linux.ibm.com>,
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CC:     "linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Sang-yoon Oh <sangyoon.oh@samsung.com>,
        Sung-Jun Park <sungjun07.park@samsung.com>,
        yongmyung lee <ymhungry.lee@samsung.com>,
        Jinyoung CHOI <j-young.choi@samsung.com>,
        Adel Choi <adel.choi@samsung.com>,
        BoRam Shin <boram.shin@samsung.com>
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> 
> > This is a patch for the HPB module.
> > The HPB module queries UFS for device information during initialization.
> > We added the export symbol to two functions in ufshcd.c to initialize
> > the HPB module.
> > 
> > The HPB module can be loaded or built-in as needed.
> > The mininum size of the memory pool used in the HPB module is
> Typo minimum
> 
> > implemented
> > as a module parameter, so that it can be configurable by the user.
> > 
> > To gurantee a minimum memory pool size of 4MB:
> > $ insmod ufshpb.ko ufshpb_host_map_kbytes=4096
> You are going through a lot of troubles to make it a loadable module.
> What are, in your opinion, the pros and cons of this design decision?

In my opinion...

pros:
1. A user can unload an unnecessary module when there is an insufficient
memory situation (HPB case).
2. Since each UFS vendor has a different way of implementing UFS features,
it can be supported as a separate module. Otherwise, many quirks must
be attached to module, which is not desirable way.
3. It is possible to distinguish parts that are not necessary for essential
ufs operation.
4. It is advantageous to implement the latest functions according to the
development speed of UFS.

cons:
1. It is difficult work to be implemented as a module.
2. Modifying "ufsfeature.c" is required to implement the feature that can
not supported by the exsiting "ufsf_operation".

Thanks,
Daejun