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SubjectRe: [PATCH v2 2/3] scsi: ufs: Modulize ufs-bsg
On 2019-12-12 12:53, Bjorn Andersson wrote:
> 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?
>

ufs-bsg is a helpful gadget for debug/test purpose. But neither
disabling it nor enabling it is the best way on a commercialized
device. Disabling it means we cannot use it, while enabling it
by default will expose all the DEVM/UIC/TM interfaces to user space,
which is not "safe" on a commercialized device to let users play with
it.
Making it a module can resolve this, because only vendors can install it
as they have the root permissions.

>>
>> 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?
>

Because ufshcd.c needs to call some funcs defined in bsg lib.

>> ---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?
>

In the case that CONFIG_SCSI_UFS_BSG=y and CONFIG_SCSI_UFS_QCOM=y,
I give late_initcall_sync(ufs_bsg_init) to make sure ufs_bsg_init
is invoked only after platform driver is probed. I tested this
combination.

In the case that both of them are "m", installing ufs-bsg before
ufs-qcom
is installed would have no effect as ufs_hba_list is empty, which is
expected.
And in real cases, as the UFS is the boot device, UFS driver will always
be probed during bootup.

>> + 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.
>

Good point, will remove it.

>> +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
>

If ufshcd is removed, its ufs-bsg, if exists, should also be removed.
Could you please enlighten me a better way to do this? Thanks.

Regards,
Can Guo.

>> + 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;
>> };
>>
>> --
>> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora
>> Forum,
>> a Linux Foundation Collaborative Project
>>

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