linux-kernel - Re: [PATCH] spi: spidev: Add compatible for external SPI ports on Kontron boards

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Date:   Thu, 2 Jul 2020 18:04:05 +0200
From:   Frieder Schrempf <frieder.schrempf@...tron.de>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Mark Brown <broonie@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-spi <linux-spi@...r.kernel.org>
Subject: Re: [PATCH] spi: spidev: Add compatible for external SPI ports on
 Kontron boards

Hi Geert,

On 02.07.20 16:57, Geert Uytterhoeven wrote:
> Hi Frieder,
> 
> On Thu, Jul 2, 2020 at 4:46 PM Frieder Schrempf
> <frieder.schrempf@...tron.de> wrote:
>> On 02.07.20 16:25, Mark Brown wrote:
>>> On Thu, Jul 02, 2020 at 04:18:46PM +0200, Schrempf Frieder wrote:
>>>> From: Frieder Schrempf <frieder.schrempf@...tron.de>
>>>>
>>>> Allow external SPI ports on Kontron boards to use the spidev driver.
>>>
>>> I'd have expected this to require loading a DT overlay for whatever's
>>> attached?
>>
>> My intention is to use the spidev driver in the default board DT for an
>> interface that is routed to an extension connector and has no dedicated
>> slave device attached onboard. So users can attach sensors, etc. with
>> userspace drivers without touching the kernel or DT.
>>
>> See https://eur04.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpatchwork.kernel.org%2Fpatch%2F11639075%2F&amp;data=02%7C01%7Cfrieder.schrempf%40kontron.de%7C5ca9f0ba0ccb4ab0329f08d81e983d4e%7C8c9d3c973fd941c8a2b1646f3942daf1%7C0%7C0%7C637292987071583819&amp;sdata=M8y9HYICQLocSgRmak6uYsx9Y%2FoukaqgmK2D0F%2FTV98%3D&amp;reserved=0 for the boards DT.
> 
> You can bind "kontron,user-spi" devices to spidev from userspace:
> [PATCH v2 0/3] device tree spidev solution - driver_override for SPI
> https://eur04.safelinks.protection.outlook.com/?url=https%3A%2F%2Fspinics.net%2Flists%2Flinux-spi%2Fmsg13951.html&amp;data=02%7C01%7Cfrieder.schrempf%40kontron.de%7C5ca9f0ba0ccb4ab0329f08d81e983d4e%7C8c9d3c973fd941c8a2b1646f3942daf1%7C0%7C0%7C637292987071583819&amp;sdata=D9pum1oTXWSt%2BY8Egb1J4DOgSa5KH3RwxsSmUl7LgUk%3D&amp;reserved=0

Thanks for pointing that out. I didn't know that this is possible.
I just tried like below it and it works like a charm:

 > echo "spidev" > 
/sys/devices/platform/soc@...0800000.bus/30840000.spi/spi_master/spi2/spi2.0/driver_override
 > echo "spi2.0" > /sys/bus/spi/drivers/spidev/bind

Thanks,
Frieder