Re: [PATCH V13 2/2] scsi: ufs: Add configfs support for UFS provisioning

[Sayali Lokhande]

On 9/19/2018 2:26 AM, Evan Green wrote:
> On Fri, Sep 14, 2018 at 2:43 AM Sayali Lokhande <sayalil@xxxxxxxxxxxxxx> wrote:
> > This patch adds configfs support to provision UFS device at
> > runtime. This feature can be primarily useful in factory or
> > assembly line as some devices may be required to be configured
> > multiple times during initial system development phase.
> > Configuration Descriptors can be written multiple times until
> > bConfigDescrLock attribute is zero.
> >
> > Configuration descriptor buffer consists of Device and Unit
> > descriptor configurable parameters which are parsed from vendor
> > specific provisioning file and then passed via configfs node at
> > runtime to provision ufs device.
> > CONFIG_CONFIGFS_FS and CONFIG_UFS_PROVISION needs to be enabled
> > for using this feature.
> >
> > Usage:
> > 1) To read current configuration descriptor with index X
> >     (where index X can be 0/1/2/3) :
> >     cat /config/<device_name>/ufs_config_desc_X
> >
> > 2) To write configuration descriptor with index X :
> >     echo <config_desc_buf> > /config/<device_name>/ufs_config_desc_X
> >
> > Signed-off-by: Sayali Lokhande <sayalil@xxxxxxxxxxxxxx>
> > ---
> ...
> > diff --git a/drivers/scsi/ufs/ufs-configfs.c b/drivers/scsi/ufs/ufs-configfs.c
> > new file mode 100644
> > index 0000000..84ccb1a
> > --- /dev/null
> > +++ b/drivers/scsi/ufs/ufs-configfs.c
> > @@ -0,0 +1,237 @@
> ...
> > +static ssize_t ufs_config_desc_0_show(struct config_item *item, char *buf)
> > +{
> > +       return ufs_config_desc_show(item, buf, 0);
> > +}
> > +
> > +static ssize_t ufs_config_desc_0_store(struct config_item *item,
> > +                                      const char *buf, size_t count)
> > +{
> > +       return ufshcd_desc_configfs_store(item, buf, count, 0);
> > +}
> > +
> > +static ssize_t ufs_config_desc_1_show(struct config_item *item, char *buf)
> > +{
> > +       return ufs_config_desc_show(item, buf, 1);
> > +}
> > +
> > +static ssize_t ufs_config_desc_1_store(struct config_item *item,
> > +                                      const char *buf, size_t count)
> > +{
> > +       return ufshcd_desc_configfs_store(item, buf, count, 1);
> > +}
> > +
> > +static ssize_t ufs_config_desc_2_show(struct config_item *item, char *buf)
> > +{
> > +       return ufs_config_desc_show(item, buf, 2);
> > +}
> > +
> > +static ssize_t ufs_config_desc_2_store(struct config_item *item,
> > +                                      const char *buf, size_t count)
> > +{
> > +       return ufshcd_desc_configfs_store(item, buf, count, 2);
> > +}
> > +
> > +static ssize_t ufs_config_desc_3_show(struct config_item *item, char *buf)
> > +{
> > +       return ufs_config_desc_show(item, buf, 3);
> > +}
> > +
> > +static ssize_t ufs_config_desc_3_store(struct config_item *item,
> > +                                      const char *buf, size_t count)
> > +{
> > +       return ufshcd_desc_configfs_store(item, buf, count, 3);
> > +}
> > +
> The copypasta above and below is not my favorite, but I suppose it's
> either this or wrap it all up in a macro that you stamp down 4 times.
> I'm not sure if that's really any cleaner, so I guess this is fine.
>
> > +static struct configfs_attribute ufshcd_attr_provision_0 = {
> > +       .ca_name        = "ufs_config_desc_0",
> > +       .ca_mode        = 0644,
> > +       .ca_owner       = THIS_MODULE,
> > +       .show           = ufs_config_desc_0_show,
> > +       .store          = ufs_config_desc_0_store,
> > +};
> > +
> > +static struct configfs_attribute ufshcd_attr_provision_1 = {
> > +       .ca_name        = "ufs_config_desc_1",
> > +       .ca_mode        = 0644,
> > +       .ca_owner       = THIS_MODULE,
> > +       .show           = ufs_config_desc_1_show,
> > +       .store          = ufs_config_desc_1_store,
> > +};
> > +
> > +static struct configfs_attribute ufshcd_attr_provision_2 = {
> > +       .ca_name        = "ufs_config_desc_2",
> > +       .ca_mode        = 0644,
> > +       .ca_owner       = THIS_MODULE,
> > +       .show           = ufs_config_desc_2_show,
> > +       .store          = ufs_config_desc_2_store,
> > +};
> > +
> > +static struct configfs_attribute ufshcd_attr_provision_3 = {
> > +       .ca_name        = "ufs_config_desc_3",
> > +       .ca_mode        = 0644,
> > +       .ca_owner       = THIS_MODULE,
> > +       .show           = ufs_config_desc_3_show,
> > +       .store          = ufs_config_desc_3_store,
> > +};
> > +
> > +static struct configfs_attribute *ufshcd_attrs[] = {
> > +       &ufshcd_attr_provision_0,
> > +       &ufshcd_attr_provision_1,
> > +       &ufshcd_attr_provision_2,
> > +       &ufshcd_attr_provision_3,
> > +       NULL,
> > +};
> > +
> > +static struct config_item_type ufscfg_type = {
> > +       .ct_attrs       = ufshcd_attrs,
> > +       .ct_owner       = THIS_MODULE,
> > +};
> > +
> > +void ufshcd_configfs_init(struct ufs_hba *hba, const char *name)
> > +{
> > +       int ret;
> > +       struct config_item *cg_item;
> > +       struct configfs_subsystem *subsys;
> > +
> > +       cg_item = &hba->subsys.su_group.cg_item;
> > +       sprintf(cg_item->ci_namebuf, "%s", name);
> CONFIGFS_ITEM_NAME_LEN is only 20. Is there anything preventing the
> device name passed in here from being longer than that? You'd have a
> nasty overrun on your hands if not. Maybe snprintf here?
Agree. I need to use snprintf here. Will update.
> > +       cg_item->ci_type = &ufscfg_type;
> > +
> > +       subsys = &hba->subsys;
> > +       config_group_init(&subsys->su_group);
> > +       mutex_init(&subsys->su_mutex);
> > +       ret = configfs_register_subsystem(subsys);
> > +       if (ret)
> > +               pr_err("Error %d while registering subsystem %s\n",
> > +                      ret,
> > +                      subsys->su_group.cg_item.ci_namebuf);
> > +}
> > +
> > +void ufshcd_configfs_exit(struct ufs_hba *hba)
> > +{
> > +       configfs_unregister_subsystem(&hba->subsys);
> > +}