linux-kernel - RE: [PATCH v2 1/3] scsi: ufs: Put SCSI host after remove it

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Message-ID: <MN2PR04MB6991CC9F97E4AE9992F96A09FC5A0@MN2PR04MB6991.namprd04.prod.outlook.com>
Date:   Wed, 11 Dec 2019 13:44:40 +0000
From:   Avri Altman <Avri.Altman@....com>
To:     "cang@...eaurora.org" <cang@...eaurora.org>
CC:     "asutoshd@...eaurora.org" <asutoshd@...eaurora.org>,
        "nguyenb@...eaurora.org" <nguyenb@...eaurora.org>,
        "rnayak@...eaurora.org" <rnayak@...eaurora.org>,
        "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "kernel-team@...roid.com" <kernel-team@...roid.com>,
        "saravanak@...gle.com" <saravanak@...gle.com>,
        "salyzyn@...gle.com" <salyzyn@...gle.com>,
        Alim Akhtar <alim.akhtar@...sung.com>,
        Pedro Sousa <pedrom.sousa@...opsys.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Stanley Chu <stanley.chu@...iatek.com>,
        Bean Huo <beanhuo@...ron.com>,
        Venkat Gopalakrishnan <venkatg@...eaurora.org>,
        Tomas Winkler <tomas.winkler@...el.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v2 1/3] scsi: ufs: Put SCSI host after remove it

 
> 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@...eaurora.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?
> >
> >
> 
> 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/sd/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.