linux-kernel - Re: [PATCH v2 2/3] scsi: ufs: Modulize ufs-bsg

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Message-ID: <9c31a7f5-a39b-02e6-350f-5fe51f1c4275@acm.org>
Date:   Fri, 13 Dec 2019 13:59:18 -0700
From:   Bart Van Assche <bvanassche@....org>
To:     Can Guo <cang@...eaurora.org>, asutoshd@...eaurora.org,
        nguyenb@...eaurora.org, rnayak@...eaurora.org,
        linux-scsi@...r.kernel.org, kernel-team@...roid.com,
        saravanak@...gle.com, salyzyn@...gle.com
Cc:     Alim Akhtar <alim.akhtar@...sung.com>,
        Avri Altman <avri.altman@....com>,
        Pedro Sousa <pedrom.sousa@...opsys.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Evan Green <evgreen@...omium.org>,
        Kishon Vijay Abraham I <kishon@...com>,
        Stephen Boyd <swboyd@...omium.org>,
        Stanley Chu <stanley.chu@...iatek.com>,
        Vignesh Raghavendra <vigneshr@...com>,
        Bean Huo <beanhuo@...ron.com>,
        Venkat Gopalakrishnan <venkatg@...eaurora.org>,
        Tomas Winkler <tomas.winkler@...el.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Arnd Bergmann <arnd@...db.de>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 2/3] scsi: ufs: Modulize ufs-bsg

On 12/11/19 3:49 AM, Can Guo wrote:
> In order to improve the flexibility of ufs-bsg, modulizing it is a good
> choice. This change introduces tristate to ufs-bsg to allow users compile
> it as an external module.

Did you perhaps mean "modularize" instead of "modulize"? Additionally, 
should "modulizing" perhaps be changed into "modularizing"?

> diff --git a/drivers/scsi/ufs/Kconfig b/drivers/scsi/ufs/Kconfig
> index d14c224..72620ce 100644
> --- a/drivers/scsi/ufs/Kconfig
> +++ b/drivers/scsi/ufs/Kconfig
> @@ -38,6 +38,7 @@ config SCSI_UFSHCD
>   	select PM_DEVFREQ
>   	select DEVFREQ_GOV_SIMPLE_ONDEMAND
>   	select NLS
> +	select BLK_DEV_BSGLIB
>   	---help---
>   	This selects the support for UFS devices in Linux, say Y and make
>   	  sure that you know the name of your UFS host adapter (the card

I do not understand the above change. Doesn't moving the BSG code into a 
separate module remove the dependency of SCSI_UFSHCD on BLK_DEV_BSGLIB?

> +static int __init ufs_bsg_init(void)
> +{
> +	struct list_head *hba_list = NULL;
> +	struct ufs_hba *hba;
> +	int ret = 0;
> +
> +	ufshcd_get_hba_list_lock(&hba_list);
> +	list_for_each_entry(hba, hba_list, list) {
> +		ret = ufs_bsg_probe(hba);
> +		if (ret)
> +			break;
> +	}
> +	ufshcd_put_hba_list_unlock();
> +
> +	return ret;
> +}

What if ufs_bsg_probe() succeeds for some UFS adapters but not for 
others? Shouldn't ufs_bgs_remove() be called in that case for the 
adapters for which ufs_bsg_probe() succeeded?

> +late_initcall_sync(ufs_bsg_init);
> +module_exit(ufs_bsg_exit);

Why late_initcall_sync() instead of module_init()?

> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> index a86b0fd..7a83a8f 100644
> --- a/drivers/scsi/ufs/ufshcd.c
> +++ b/drivers/scsi/ufs/ufshcd.c
> @@ -108,6 +108,22 @@
>   		       16, 4, buf, __len, false);                        \
>   } while (0)
>   
> +static LIST_HEAD(ufs_hba_list);
> +static DEFINE_MUTEX(ufs_hba_list_lock);
> +
> +void ufshcd_get_hba_list_lock(struct list_head **list)
> +{
> +	mutex_lock(&ufs_hba_list_lock);
> +	*list = &ufs_hba_list;
> +}
> +EXPORT_SYMBOL_GPL(ufshcd_get_hba_list_lock);

Please make ufshcd_get_hba_list_lock() return the list_head pointer 
instead of the above.

Thanks,

Bart.