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From:   Avri Altman <Avri.Altman@wdc.com>
To:     "cang@codeaurora.org" <cang@codeaurora.org>
CC:     "asutoshd@codeaurora.org" <asutoshd@codeaurora.org>,
        "nguyenb@codeaurora.org" <nguyenb@codeaurora.org>,
        "rnayak@codeaurora.org" <rnayak@codeaurora.org>,
        "linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
        "kernel-team@android.com" <kernel-team@android.com>,
        "saravanak@google.com" <saravanak@google.com>,
        "salyzyn@google.com" <salyzyn@google.com>,
        Alim Akhtar <alim.akhtar@samsung.com>,
        Pedro Sousa <pedrom.sousa@synopsys.com>,
        "James E.J. Bottomley" <jejb@linux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@oracle.com>,
        Stanley Chu <stanley.chu@mediatek.com>,
        Bean Huo <beanhuo@micron.com>,
        Venkat Gopalakrishnan <venkatg@codeaurora.org>,
        Tomas Winkler <tomas.winkler@intel.com>,
        open list <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH v2 1/3] scsi: ufs: Put SCSI host after remove it
Thread-Topic: [PATCH v2 1/3] scsi: ufs: Put SCSI host after remove it
Thread-Index: AQHVr//RJYxYdS3dXUmhxTnGX2MLCqe0vdGQgAAIXgCAAANkQIAABwUAgAAhY6A=
Date:   Wed, 11 Dec 2019 13:44:40 +0000
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=20
> On 2019-12-11 19:22, Avri Altman wrote:
> >>
> >>
> >> On 2019-12-11 18:37, Avri Altman wrote:
> >> >>
> >> >> In ufshcd_remove(), after SCSI host is removed, put it once so
> >> >> that its resources can be released.
> >> >>
> >> >> Signed-off-by: Can Guo <cang@codeaurora.org>
> >> >
> >> > This is not really part of this patchset, is it?
> >> >
> >>
> >> Hi Avri,
> >>
> >> I put this change in the same patchset due to #1. The main patch has
> >> dependency on it #2. Consider a scenario where platform driver is
> >> also compiled as a module, say ufs_qcom.ko.
> >>      In this case, we have two modules, ufs-qcom.ko and ufs-bsg.ko.
> >> If do insmod ufs-qcom.ko
> >>      then rmmod ufs-qcom.ko and do insmod ufs-qcom.ko again, without
> >> this change, because scsi
> >>      host was not release, the new scsi host will have a different
> >> host number, meaning
> >>      hba->host->host_no will be 1, but not 0. Now if do insmod
> >> ufs-bsg.ko now, the ufs-bsg dev
> >>      created in /dev/bsg/ will be ufs-bsg1, but not ufs-bsg0. If keep
> >> trying these operations,
> >>      the ufs-bsg device's name will be messed up. This change make
> >> sure after ufs- qcom.ko is removed
> >>      and installed back, its hba->host->host_no stays 0, so that
> >> ufs-bsg device name stays same.
> > Looks like we needed to manage the ufs-bsg nodes using an IDA, instead
> > of host_no?
> >
> >
>=20
> Marking one ufs-bsg dev with host_no still has its advantage. If we have =
more
> than one hba host, we can find the right ufs-bsgX dev by reading the sg/s=
d/bsg
> device's host->host_unique_id (through SCSI_IOCTL_GET_IDLUN for example).
> But If ufs-bsg has its own ID, we will lost this "mapping".
OK.