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

Bjorn Andersson
2019-12-12T04:54:03Z

On Wed 11 Dec 00:49 PST 2019, 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.

Can you please elaborate on what this "flexibility" is and why it's a
good thing?

>
> Signed-off-by: Can Guo <cang@codeaurora.org>
> ---
> drivers/scsi/ufs/Kconfig | 3 ++-
> drivers/scsi/ufs/Makefile | 2 +-
> drivers/scsi/ufs/ufs_bsg.c | 49 +++++++++++++++++++++++++++++++++++++++++++---
> drivers/scsi/ufs/ufs_bsg.h | 8 --------
> drivers/scsi/ufs/ufshcd.c | 36 ++++++++++++++++++++++++++++++----
> drivers/scsi/ufs/ufshcd.h | 7 ++++++-
> 6 files changed, 87 insertions(+), 18 deletions(-)
>
> 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

Why is this needed?

> ---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
> @@ -143,7 +144,7 @@ config SCSI_UFS_TI_J721E
> If unsure, say N.
>
> config SCSI_UFS_BSG
> - bool "Universal Flash Storage BSG device node"
> + tristate "Universal Flash Storage BSG device node"
> depends on SCSI_UFSHCD
> select BLK_DEV_BSGLIB
> help
> diff --git a/drivers/scsi/ufs/Makefile b/drivers/scsi/ufs/Makefile
> index 94c6c5d..904eff1 100644
> --- a/drivers/scsi/ufs/Makefile
> +++ b/drivers/scsi/ufs/Makefile
> @@ -6,7 +6,7 @@ obj-$(CONFIG_SCSI_UFS_CDNS_PLATFORM) += cdns-pltfrm.o
> obj-$(CONFIG_SCSI_UFS_QCOM) += ufs-qcom.o
> obj-$(CONFIG_SCSI_UFSHCD) += ufshcd-core.o
> ufshcd-core-y += ufshcd.o ufs-sysfs.o
> -ufshcd-core-$(CONFIG_SCSI_UFS_BSG) += ufs_bsg.o
> +obj-$(CONFIG_SCSI_UFS_BSG) += ufs_bsg.o
> obj-$(CONFIG_SCSI_UFSHCD_PCI) += ufshcd-pci.o
> obj-$(CONFIG_SCSI_UFSHCD_PLATFORM) += ufshcd-pltfrm.o
> obj-$(CONFIG_SCSI_UFS_HISI) += ufs-hisi.o
> diff --git a/drivers/scsi/ufs/ufs_bsg.c b/drivers/scsi/ufs/ufs_bsg.c
> index 3a2e68f..302222f 100644
> --- a/drivers/scsi/ufs/ufs_bsg.c
> +++ b/drivers/scsi/ufs/ufs_bsg.c
> @@ -164,13 +164,15 @@ static int ufs_bsg_request(struct bsg_job *job)
> */
> void ufs_bsg_remove(struct ufs_hba *hba)
> {
> - struct device *bsg_dev = &hba->bsg_dev;
> + struct device *bsg_dev = hba->bsg_dev;
>
> if (!hba->bsg_queue)
> return;
>
> bsg_remove_queue(hba->bsg_queue);
>
> + hba->bsg_dev = NULL;
> + hba->bsg_queue = NULL;
> device_del(bsg_dev);
> put_device(bsg_dev);
> }
> @@ -178,6 +180,7 @@ void ufs_bsg_remove(struct ufs_hba *hba)
> static inline void ufs_bsg_node_release(struct device *dev)
> {
> put_device(dev->parent);
> + kfree(dev);
> }
>
> /**
> @@ -186,14 +189,19 @@ static inline void ufs_bsg_node_release(struct device *dev)
> *
> * Called during initial loading of the driver, and before scsi_scan_host.
> */
> -int ufs_bsg_probe(struct ufs_hba *hba)
> +static int ufs_bsg_probe(struct ufs_hba *hba)
> {
> - struct device *bsg_dev = &hba->bsg_dev;
> + struct device *bsg_dev;
> struct Scsi_Host *shost = hba->host;
> struct device *parent = &shost->shost_gendev;
> struct request_queue *q;
> int ret;
>
> + bsg_dev = kzalloc(sizeof(*bsg_dev), GFP_KERNEL);
> + if (!bsg_dev)
> + return -ENOMEM;
> +
> + hba->bsg_dev = bsg_dev;
> device_initialize(bsg_dev);
>
> bsg_dev->parent = get_device(parent);
> @@ -217,6 +225,41 @@ int ufs_bsg_probe(struct ufs_hba *hba)
>
> out:
> dev_err(bsg_dev, "fail to initialize a bsg dev %d\n", shost->host_no);
> + hba->bsg_dev = NULL;
> put_device(bsg_dev);
> return ret;
> }
> +
> +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;
> + }

So what happens if I go CONFIG_SCSI_UFS_BSG=y and
CONFIG_SCSI_UFS_QCOM=y?

Wouldn't that mean that ufs_bsg_init() is called before ufshcd_init()
has added the controller to the list? And even in the even that they are
both =m, what happens if they are invoked in the "wrong" order?

> + ufshcd_put_hba_list_unlock();
> +
> + return ret;
> +}
> +
> +static void __exit ufs_bsg_exit(void)
> +{
> + struct list_head *hba_list = NULL;
> + struct ufs_hba *hba;
> +
> + ufshcd_get_hba_list_lock(&hba_list);
> + list_for_each_entry(hba, hba_list, list)
> + ufs_bsg_remove(hba);
> + ufshcd_put_hba_list_unlock();
> +}
> +
> +late_initcall_sync(ufs_bsg_init);
> +module_exit(ufs_bsg_exit);
> +
> +MODULE_ALIAS("ufs-bsg");

The purpose of MODULE_ALIAS() is to facilitate module autoloading, but
as you probe the bsg device from the initcall of the bsg driver itself I
don't see how that would happen, and as such I don't think this alias
has a purpose.

> +MODULE_LICENSE("GPL v2");
> diff --git a/drivers/scsi/ufs/ufs_bsg.h b/drivers/scsi/ufs/ufs_bsg.h
> index d099187..9d922c0 100644
> --- a/drivers/scsi/ufs/ufs_bsg.h
> +++ b/drivers/scsi/ufs/ufs_bsg.h
> @@ -12,12 +12,4 @@
> #include "ufshcd.h"
> #include "ufs.h"
>
> -#ifdef CONFIG_SCSI_UFS_BSG
> -void ufs_bsg_remove(struct ufs_hba *hba);
> -int ufs_bsg_probe(struct ufs_hba *hba);
> -#else
> -static inline void ufs_bsg_remove(struct ufs_hba *hba) {}
> -static inline int ufs_bsg_probe(struct ufs_hba *hba) {return 0; }
> -#endif
> -
> #endif /* UFS_BSG_H */
> 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);
> +
> +void ufshcd_put_hba_list_unlock(void)
> +{
> + mutex_unlock(&ufs_hba_list_lock);
> +}
> +EXPORT_SYMBOL_GPL(ufshcd_put_hba_list_unlock);
> +
> int ufshcd_dump_regs(struct ufs_hba *hba, size_t offset, size_t len,
> const char *prefix)
> {
> @@ -2093,6 +2109,7 @@ int ufshcd_send_uic_cmd(struct ufs_hba *hba, struct uic_command *uic_cmd)
> ufshcd_release(hba);
> return ret;
> }
> +EXPORT_SYMBOL_GPL(ufshcd_send_uic_cmd);
>
> /**
> * ufshcd_map_sg - Map scatter-gather list to prdt
> @@ -6024,6 +6041,7 @@ int ufshcd_exec_raw_upiu_cmd(struct ufs_hba *hba,
>
> return err;
> }
> +EXPORT_SYMBOL_GPL(ufshcd_exec_raw_upiu_cmd);
>
> /**
> * ufshcd_eh_device_reset_handler - device reset handler registered to
> @@ -7043,9 +7061,6 @@ static int ufshcd_probe_hba(struct ufs_hba *hba)
> }
> hba->clk_scaling.is_allowed = true;
> }
> -
> - ufs_bsg_probe(hba);
> -
> scsi_scan_host(hba->host);
> pm_runtime_put_sync(hba->dev);
> }
> @@ -8248,7 +8263,16 @@ int ufshcd_shutdown(struct ufs_hba *hba)
> */
> void ufshcd_remove(struct ufs_hba *hba)
> {
> - ufs_bsg_remove(hba);
> + struct device *bsg_dev = hba->bsg_dev;
> +
> + mutex_lock(&ufs_hba_list_lock);
> + list_del(&hba->list);
> + if (hba->bsg_queue) {
> + bsg_remove_queue(hba->bsg_queue);
> + device_del(bsg_dev);

Am I reading this correct in that you probe the bsg_dev form initcall
and you delete it as the ufshcd instance is removed? That's not okay.

Regards,
Bjorn

> + put_device(bsg_dev);
> + }
> + mutex_unlock(&ufs_hba_list_lock);
> ufs_sysfs_remove_nodes(hba->dev);
> scsi_remove_host(hba->host);
> scsi_host_put(hba->host);
> @@ -8494,6 +8518,10 @@ int ufshcd_init(struct ufs_hba *hba, void __iomem *mmio_base, unsigned int irq)
> async_schedule(ufshcd_async_scan, hba);
> ufs_sysfs_add_nodes(hba->dev);
>
> + mutex_lock(&ufs_hba_list_lock);
> + list_add_tail(&hba->list, &ufs_hba_list);
> + mutex_unlock(&ufs_hba_list_lock);
> +
> return 0;
>
> out_remove_scsi_host:
> diff --git a/drivers/scsi/ufs/ufshcd.h b/drivers/scsi/ufs/ufshcd.h
> index 2740f69..893debc 100644
> --- a/drivers/scsi/ufs/ufshcd.h
> +++ b/drivers/scsi/ufs/ufshcd.h
> @@ -74,6 +74,9 @@
>
> struct ufs_hba;
>
> +void ufshcd_get_hba_list_lock(struct list_head **list);
> +void ufshcd_put_hba_list_unlock(void);
> +
> enum dev_cmd_type {
> DEV_CMD_TYPE_NOP = 0x0,
> DEV_CMD_TYPE_QUERY = 0x1,
> @@ -473,6 +476,7 @@ struct ufs_stats {
>
> /**
> * struct ufs_hba - per adapter private structure
> + * @list: Anchored at ufs_hba_list
> * @mmio_base: UFSHCI base register address
> * @ucdl_base_addr: UFS Command Descriptor base address
> * @utrdl_base_addr: UTP Transfer Request Descriptor base address
> @@ -527,6 +531,7 @@ struct ufs_stats {
> * @scsi_block_reqs_cnt: reference counting for scsi block requests
> */
> struct ufs_hba {
> + struct list_head list;
> void __iomem *mmio_base;
>
> /* Virtual memory reference */
> @@ -734,7 +739,7 @@ struct ufs_hba {
> struct ufs_desc_size desc_size;
> atomic_t scsi_block_reqs_cnt;
>
> - struct device bsg_dev;
> + struct device *bsg_dev;
> struct request_queue *bsg_queue;
> };
>
> --
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> a Linux Foundation Collaborative Project
>