linux-kernel - Re: [PATCH 3/4] fix module autoloading for ACPI enumerated devices

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Message-ID: <20140113173525.GF29039@sirena.org.uk>
Date:	Mon, 13 Jan 2014 17:35:25 +0000
From:	Mark Brown <broonie@...nel.org>
To:	Zhang Rui <rui.zhang@...el.com>
Cc:	linux-kernel@...r.kernel.org, linux-i2c@...r.kernel.org,
	linux-spi@...r.kernel.org, rjw@...ysocki.net,
	grant.likely@...retlab.ca, jarkko.nikula@...ux.intel.com,
	mika.westerberg@...ux.intel.com
Subject: Re: [PATCH 3/4] fix module autoloading for ACPI enumerated devices

On Mon, Jan 13, 2014 at 09:48:31PM +0800, Zhang Rui wrote:
> ACPI enumerated devices has ACPI style _HID and _CID strings,
> all of these strings can be used for both driver loading and matching.

> But currently, in Platform, I2C and SPI bus, only the ACPI style
> driver matching is supported by invoking acpi_driver_match_device()
> in bus .match() callback.

I don't understand what this means, sorry.  As far as I can tell "ACPI
style _HID and _CID strings" are something different to "ACPI style
driver matching" but what that actually means is not at all clear to me
so I don't know what problem this is intended to fix.

Please also always remember to CC maintainers on patches.

> diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
> index 349ebba..ab70eda 100644
> --- a/drivers/spi/spi.c
> +++ b/drivers/spi/spi.c
> @@ -58,6 +58,11 @@ static ssize_t
>  modalias_show(struct device *dev, struct device_attribute *a, char *buf)
>  {
>  	const struct spi_device	*spi = to_spi_device(dev);
> +	int len;
> +
> +	len = acpi_device_modalias(dev, buf, PAGE_SIZE);
> +	if (len != -ENODEV)
> +		return len;
>  
>  	return sprintf(buf, "%s%s\n", SPI_MODULE_PREFIX, spi->modalias);
>  }

What does this do and why can't acpi_driver_match_device() handle this
like it does for other ACPI devices?  We don't need to add such code for
other firmware interfaces...

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