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

[Evan Green]

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?

> +       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);
> +}