linux-kernel - Re: [PATCH 1/3] ACPI: add module autoloading support for ACPI enumerated devices

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Message-ID: <1381749388.2034.28.camel@rzhang1-mobl4>
Date:	Mon, 14 Oct 2013 19:16:28 +0800
From:	Zhang Rui <rui.zhang@...el.com>
To:	Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc:	rjw@...k.pl, linux-acpi@...r.kernel.org, linux-i2c@...r.kernel.org,
	linux-kernel@...r.kernel.org, jarkko.nikula@...ux.intel.com
Subject: Re: [PATCH 1/3] ACPI: add module autoloading support for ACPI
 enumerated devices

On Mon, 2013-10-14 at 13:14 +0300, Mika Westerberg wrote:
> On Mon, Oct 14, 2013 at 05:10:32PM +0800, Zhang Rui wrote:
> > An ACPI enumerated device may have its compatible id strings.
> > 
> > To support the compatible ACPI ids (acpi_device->pnp.ids),
> > we introduced acpi_driver_match_device() to match
> > the driver->acpi_match_table and acpi_device->pnp.ids.
> > 
> > For those drivers, MODULE_DEVICE_TABLE(acpi, xxx) is used to
> > exports the driver module alias in the format of
> > "acpi:device_compatible_ids".
> > But in the mean time, the current code does not export the
> > ACPI compatible strings as part of the module_alias for the
> > ACPI enumerated devices, which will break the module autoloading.
> > 
> > Take the following piece of code for example,
> > static const struct acpi_device_id xxx_acpi_match[] = {
> >         { "INTABCD", 0 },
> >         { }
> > };
> > MODULE_DEVICE_TABLE(acpi, xxx_acpi_match);
> > 
> > If this piece of code is used in a platform driver for
> > an ACPI enumerated platform device, the platform driver module_alias
> > is "acpi:INTABCD", but the uevent attribute of its platform device node
> > is "platform:INTABCD:00" (PREFIX:pdev->name).
> > If this piece of code is used in an i2c driver for an ACPI enumerated
> > i2c device, the i2c driver module_alias is "acpi:INTABCD", but
> > the uevent of its i2c device node is "i2c:INTABCD:00" (PREFIX:client->name).
> > 
> > The reason why the module autoloading is not broken for now is that
> > the uevent file of the ACPI device node is "acpi:INTABCD".
> > Thus it is the ACPI device node creation that loads the platform/i2c driver.
> > 
> > So this is a problem that will affect us the day when the ACPI bus
> > is removed from device model.
> > 
> > This patch introduces a new function to exporting ACPI ids as the
> > module_alias, for the ACPI enumerate devices.
> > 
> > For any drivers using MODULE_DEVICE_TALBE(acpi, blabla), the uevent file
>                                         ^ TABLE?
> 
> > of its associated device must be fixed by invoking this function.
> > 
> > Signed-off-by: Zhang Rui <rui.zhang@...el.com>
> 
> Makes sense. There is one comment below but other than that, you can add
> my,
> 
> Reviewed-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
> 
Thanks for reviewing.

> For the three patches.
> 
> I wonder if we should do the same for SPI bus as well?
> 
yes, you are right.
Actually, I should check for buses that supports
acpi_driver_match_device() and fix them all.
Will add it in next version.

thanks,
rui
> > ---
> >  drivers/acpi/scan.c  |   24 ++++++++++++++++++++++++
> >  include/linux/acpi.h |    8 ++++++++
> >  2 files changed, 32 insertions(+)
> > 
> > diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
> > index 407ad13..db6f879 100644
> > --- a/drivers/acpi/scan.c
> > +++ b/drivers/acpi/scan.c
> > @@ -111,6 +111,30 @@ static int create_modalias(struct acpi_device *acpi_dev, char *modalias,
> >  	return len;
> >  }
> >  
> > +int acpi_device_uevent_modalias(struct device *dev, struct kobj_uevent_env *env)
> > +{
> > +	struct acpi_device *acpi_dev;
> > +	int result;
> > +	int len;
> > +
> > +	result = acpi_bus_get_device(ACPI_HANDLE(dev), &acpi_dev);
> > +	if (result)
> > +		return result;
> > +
> > +	if (list_empty(&acpi_dev->pnp.ids))
> > +		return 0;
> > +
> > +	if (add_uevent_var(env, "MODALIAS="))
> > +		return -ENOMEM;
> > +	len = create_modalias(acpi_dev, &env->buf[env->buflen - 1],
> > +				sizeof(env->buf) - env->buflen);
> > +	if (len >= (sizeof(env->buf) - env->buflen))
> > +		return -ENOMEM;
> > +	env->buflen += len;
> > +	return 0;
> > +}
> > +EXPORT_SYMBOL(acpi_device_uevent_modalias);
> 
> _GPL?


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