linux-kernel - Re: [PATCH v3 1/3] eeprom: at24: avoid adjusting offset for 24AA025E{48, 64}

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Date: Mon, 1 Jul 2024 10:20:03 +0000
From: <Andrei.Simion@...rochip.com>
To: <brgl@...ev.pl>
CC: <robh@...nel.org>, <krzk+dt@...nel.org>, <conor+dt@...nel.org>,
	<Nicolas.Ferre@...rochip.com>, <alexandre.belloni@...tlin.com>,
	<claudiu.beznea@...on.dev>, <arnd@...db.de>, <gregkh@...uxfoundation.org>,
	<linux-i2c@...r.kernel.org>, <devicetree@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>,
	<claudiu.beznea@...rochip.com>
Subject: Re: [PATCH v3 1/3] eeprom: at24: avoid adjusting offset for
 24AA025E{48, 64}

On 01.07.2024 11:46, Bartosz Golaszewski wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> On Mon, Jul 1, 2024 at 9:23 AM <Andrei.Simion@...rochip.com> wrote:
>>
>>>>
>>>> For those types of eeprom 24AA025E{48, 64} adjusting offset is not required (at24_get_offset_adj()).
>>>> So, indeed, it is an entanglement in logic.
>>>> To keep the implementation as it is:
>>>> adjoff (which is a flag that indicates when to use the adjusting offset) needs to be 1 for old compatibles but for these new ones needs to be 0.
>>>>
>>>> I think that is enough not to break the existing users. What are your thoughts?
>>>>
>>>
>>> Wait... is the adjoff field effectively a boolean? Why u8?
>>>
>>
>> struct at24_data contains offset_adj which will get value calling at24_get_offset_adj()) if adjoff is true (1).
>> Yes, adjoff needs to be treated as a boolean. I will change it in the next version.
>>
> 
> No, wait. Why can't you just do:
> 
> AT24_CHIP_DATA(at24_data_24aa025e48, 48 / 8, AT24_FLAG_READONLY);
> 
> and avoid this whole new macro variant entirely?
> 

just AT24_CHIP_DATA(at24_data_24aa025e48, 48 / 8, AT24_FLAG_READONLY):
# hexdump -C /sys/bus/nvmem/devices/1-00532/cells/eui48@fa\,0
00000000  ff ff ff ff ff ff                                 |......|
00000006
# hexdump -C /sys/bus/nvmem/devices/1-00521/cells/eui48@fa\,0
00000000  ff ff ff ff ff ff                                 |......|
00000006

with this patch (adjoff false and new macro)
# hexdump -C /sys/bus/nvmem/devices/1-00521/cells/eui48@fa\,0
00000000  04 91 62 [the rest bytes]                                 |..b...|
00000006
# hexdump -C /sys/bus/nvmem/devices/1-00532/cells/eui48@fa\,0
00000000  04 91 62 [the rest bytes]                                 |..b..m|
00000006
#

> Bart

-- 
Andrei Simion
MPU32 Engineer|Microchip Technology Inc.