linux-kernel - Re: [PATCH] mtd: fix size in mtd_info

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Date:   Fri, 16 Jul 2021 08:34:45 -0500
From:   Rob Landley <rob@...dley.net>
To:     Miquel Raynal <miquel.raynal@...tlin.com>,
        Miaohe Lin <linmiaohe@...wei.com>
Cc:     richard@....at, vigneshr@...com, David.Woodhouse@...el.com,
        Artem.Bityutskiy@...ia.com, ext-adrian.hunter@...ia.com,
        linux-kernel@...r.kernel.org, linux-mtd@...ts.infradead.org,
        linfeilong@...wei.com
Subject: Re: [PATCH] mtd: fix size in mtd_info_user to support 64-bit

On 7/16/21 4:48 AM, Miquel Raynal wrote:
> Hi Miaohe,
> 
> Miaohe Lin <linmiaohe@...wei.com> wrote on Fri, 16 Jul 2021 09:42:19
> +0800:
> 
>> On 2021/7/16 7:02, Miquel Raynal wrote:
>> > Hi Miaohe,
>> > 
>> > Miaohe Lin <linmiaohe@...wei.com> wrote on Thu, 8 Jul 2021 21:13:59
>> > +0800:
>> >   
>> >> From: Feilong Lin <linfeilong@...wei.com>
>> >>
>> >> The size in struct mtd_info_user is 32-bit, which will cause errors
>> >> when obtaining the size of large-capacity MTD devices, such as TLC
>> >> NAND FLASH-2048Gb.  
>> > 
>> > Besides the fact that such devices are far from being supported by the
>> > Linux kernel, this change would basically break userspace, it cannot
>> > enter as-is...
>> >   
>> 
>> I see. Many thanks for your reply! We're working with these large-capacity
>> MTD devices now, any suggestion to work around this?
> 
> The only way is to create a second UAPI.

Twelve years ago a patch was submitted to add a 64 bit MTD api:

  https://lwn.net/Articles/326418/

But for some reason they only merged 64 bit erase:

  https://github.com/torvalds/linux/commit/0dc54e9f33e2

But NOT the rest of the 64 bit mtd API in the same patch. I've never understood why.

Rob