linux-kernel - Re: [PATCHv4] MTD: New ioctl calls for >4GiB device support

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Date:	Tue, 31 Mar 2009 09:31:40 +0300
From:	Artem Bityutskiy <dedekind@...radead.org>
To:	Kevin Cernekee <kpc.mtd@...il.com>
Cc:	dwmw2@...radead.org, linux-mtd@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCHv4] MTD: New ioctl calls for >4GiB device support

On Mon, 2009-03-30 at 18:14 -0700, Kevin Cernekee wrote:
>  #define MTD_ABSENT		0
>  #define MTD_RAM			1
>  #define MTD_ROM			2
> @@ -50,14 +64,25 @@ struct mtd_oob_buf {
>  struct mtd_info_user {
>  	uint8_t type;
>  	uint32_t flags;
> -	uint32_t size;	 // Total size of the MTD
> +	uint32_t size;			/* Total size of the MTD */
> +	uint32_t erasesize;
> +	uint32_t writesize;
> +	uint32_t oobsize;		/* OOB bytes per page (e.g. 16) */
> +	uint32_t ecctype;		/* Obsolete, always reports -1 */
> +	uint32_t eccsize;		/* Obsolete, always reports 0 */
> +};
> +
> +struct mtd_info_user64 {
> +	uint32_t type;
> +	uint32_t flags;
> +	uint64_t size;			/* Total size of the MTD */
> +	uint32_t res0;
>  	uint32_t erasesize;
> +	uint32_t res1;
>  	uint32_t writesize;
> -	uint32_t oobsize;   // Amount of OOB data per block (e.g. 16)
> -	/* The below two fields are obsolete and broken, do not use them
> -	 * (TODO: remove at some point) */
> -	uint32_t ecctype;
> -	uint32_t eccsize;
> +	uint32_t res2;
> +	uint32_t oobsize;		/* OOB bytes per page (e.g. 16) */
> +	uint32_t res3[32];
>  };
> 
>  struct region_info_user {
> @@ -68,6 +93,18 @@ struct region_info_user {
>  	uint32_t regionindex;
>  };
> 
> +struct region_info_user64 {
> +	uint64_t offset;		/* At which this region starts,
> +					 * from the beginning of the MTD */
> +	uint32_t res0;
> +	uint32_t erasesize;		/* For this region */
> +	uint32_t res1;
> +	uint32_t numblocks;		/* Number of blocks in this region */
> +	uint32_t res2;
> +	uint32_t regionindex;
> +	uint32_t res3[16];
> +};

Your arguments vs. ioctls are valid, but sysfs is still better, because
ioctls are not very extendible. E.g., UBI utilities need sub-page size,
but ioctl's do not provide it, and I have no possibility to ask the
kernel about this. And I cannot add it, at least to old ioctls. With
sysfs, I can just add a sysfs file. This is much better.

David Brownell send 2 patches very recently which add sysfs to
MTD. I would recommend you to take them and work on top, and export
information via sysfs, still...

Thanks.

-- 
Best regards,
Artem Bityutskiy (Битюцкий Артём)

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