linux-kernel - Re: [PATCH] spi: spidev: Fix so the module is autoloaded when built as external

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Message-ID: <124e3214-37b9-524b-7888-a31e8cb455da@axis.com>
Date:   Tue, 5 Jan 2021 10:44:21 +0100
From:   Gustav Wiklander <gustavwi@...s.com>
To:     Mark Brown <broonie@...nel.org>,
        Gustav Wiklander <gustav.wiklander@...s.com>
CC:     <kernel@...s.com>, <linux-spi@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] spi: spidev: Fix so the module is autoloaded when built
 as external

On 1/4/21 10:34 PM, Mark Brown wrote:
> On Mon, Jan 04, 2021 at 04:34:35PM +0100, Gustav Wiklander wrote:
>> From: Gustav Wiklander <gustavwi@...s.com>
>>
>> The spi framework sets the modalias for the spi device to belong in
>> either the acpi device table or the SPI device table. It can never
>> be in the OF table. Therefore the spidev driver should populate the
>> spi device table rather than the OF table.
>>
>> NOTE: platform drivers and i2c drivers support aliases in the
>>        OF device table.
> 
> Why is this a good solution rather than ensuring the the OF IDs can be
> used directly?
> 

Hi Mark,

You suggestion is of course a solid alternative forward. However, the 
downside with supporting the OF device table for automatic module 
loading is that a lot of spi device drivers must be updated. Also
it is unclear what is the preferred way to do this in the kernel see
this patch:
https://lore.kernel.org/lkml/20190618052644.32446-1-bjorn.andersson@linaro.org/

If adding support of OF device table the spi device drivers must now 
include a MODULE_DEVICE_TABLE(of,...) as the spi device alias will no 
longer match the alias in the module.

This command gives 186 spi device drivers.
git grep "MODULE_DEVICE_TABLE(spi" | wc -l 

186

Best regards
Gustav Wiklander