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Date: Sun, 24 Jun 2018 15:12:32 +0200
From: Boris Brezillon <boris.brezillon@bootlin.com>
To: Richard Weinberger <richard@nod.at>
Cc: linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 12/14] ubi: uapi: Add mode selector to attach request
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On Wed, 13 Jun 2018 23:23:42 +0200
Richard Weinberger <richard@nod.at> wrote:

> This allows userspace, ubiattach, to force a full scan.
> 
> Signed-off-by: Richard Weinberger <richard@nod.at>
> ---
>  include/uapi/mtd/ubi-user.h | 14 +++++++++++++-
>  1 file changed, 13 insertions(+), 1 deletion(-)
> 
> diff --git a/include/uapi/mtd/ubi-user.h b/include/uapi/mtd/ubi-user.h
> index 5b04a494d139..cc0e54cfa7f9 100644
> --- a/include/uapi/mtd/ubi-user.h
> +++ b/include/uapi/mtd/ubi-user.h
> @@ -235,12 +235,19 @@ enum {
>  	UBI_VOL_PROP_DIRECT_WRITE = 1,
>  };
>  
> +enum {
> +	UBI_ATTACH_MODE_AUTO = 0x0,
> +	UBI_ATTACH_MODE_SCAN = 0x1,
> +	UBI_ATTACH_MODE_MAX = UBI_ATTACH_MODE_SCAN,
> +};
> +
>  /**
>   * struct ubi_attach_req - attach MTD device request.
>   * @ubi_num: UBI device number to create
>   * @mtd_num: MTD device number to attach
>   * @vid_hdr_offset: VID header offset (use defaults if %0)
>   * @max_beb_per1024: maximum expected number of bad PEB per 1024 PEBs
> + * @attach_mode: selects the attach mode
>   * @padding: reserved for future, not used, has to be zeroed
>   *
>   * This data structure is used to specify MTD device UBI has to attach and the
> @@ -276,13 +283,18 @@ enum {
>   * eraseblocks for new bad eraseblocks, but attempts to use available
>   * eraseblocks (if any). The accepted range is 0-768. If 0 is given, the
>   * default kernel value of %CONFIG_MTD_UBI_BEB_LIMIT will be used.
> + *
> + * @attach_mode is %UBI_ATTACH_MODE_AUTO by default, and let's the UBI
> + * implementation decide how to attach. If %UBI_ATTACH_MODE_SCAN is selected
> + * a full scan is forced.
>   */
>  struct ubi_attach_req {
>  	__s32 ubi_num;
>  	__s32 mtd_num;
>  	__s32 vid_hdr_offset;
>  	__s16 max_beb_per1024;
> -	__s8 padding[10];
> +	__s8 attach_mode;
> +	__s8 padding[9];
>  };

Looks like the force full-scan is just a flag, and we might need other
flags to encode things that are not related to attach mode, so how
about creating an __u16 flags field here and defining

#define UBI_ATTACH_FLG_FORCE_FULL_SCAN		0x1

?