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

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Date:   Sat, 17 Jul 2021 09:55:58 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     Rob Landley <rob@...dley.net>,
        Miquel Raynal <miquel.raynal@...tlin.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 2021/7/16 21:34, Rob Landley wrote:
> 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
> .
> 

Many thanks for both of you! This really helps! :)