linux-kernel - Re: [PATCH v1 3/3] spi: xilinx: Make num_chipselect 8-bit in the struct xspi_platform

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Message-ID: <58dca460-d363-432d-9ea7-7f29ec9c4050@amd.com>
Date: Fri, 8 Mar 2024 15:00:55 +0100
From: Michal Simek <michal.simek@....com>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: linux-spi@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-kernel@...r.kernel.org, Mark Brown <broonie@...nel.org>
Subject: Re: [PATCH v1 3/3] spi: xilinx: Make num_chipselect 8-bit in the
 struct xspi_platform_data



On 3/8/24 14:55, Andy Shevchenko wrote:
> On Fri, Mar 08, 2024 at 02:48:04PM +0100, Michal Simek wrote:
>> On 3/8/24 14:31, Andy Shevchenko wrote:
>>> On Fri, Mar 08, 2024 at 09:20:23AM +0100, Michal Simek wrote:
>>>> On 3/7/24 16:43, Andy Shevchenko wrote:
> 
> ...
> 
>>>>>     struct xspi_platform_data {
>>>>> -	u16 num_chipselect;
>>>>> -	u8 bits_per_word;
>>>>> -	struct spi_board_info *devices;
>>>>> -	u8 num_devices;
>>>>>     	bool force_irq;
>>>>> +	u8 num_chipselect;
>>>>> +	u8 bits_per_word;
>>>>> +	u8 num_devices;
>>>>
>>>> all above have 32bits. It means on 64bit cpu you have 32bit gap here.
>>>
>>>>> +	struct spi_board_info *devices;
>>>
>>> On all architectures? I mean do all 64-bit architecture ABIs _require_
>>> the pointer to be aligned at 8-byte boundary? Even if so, the struct
>>> itself can be aligned on 4-byte boundary.
>>
>> I am not able to tell if toolchain enforce 8byte alignment by default/by
>> setup on all 64bit systems.
>> I am using pahole to check this which was recommended by Greg in past which
>> reports gap in the middle.
> 
> I see, thanks for explanation.
> 
> Yes, it's likely that in some cases it will be a gap on 64-bit platforms, but
> after this patch no gap on 32-bit. Do you still want me to reshuffle that as
> you suggested?

Yes I would prefer to do that change when you are doing cleanup.

M