Re: [PATCH] i2c: Fix modalias for ACPI enumerated I2C devices

[Zhang Rui <rui.zhang@intel.com>]

On Mon, 2013-10-14 at 20:47 +0800, Zhang Rui wrote:
> On Mon, 2013-10-14 at 14:18 +0300, Jarkko Nikula wrote:
> > On 10/14/2013 12:23 PM, Zhang Rui wrote:
> > > Hi,
> > >
> > > On Thu, 2013-10-10 at 17:17 +0300, Jarkko Nikula wrote:
> > >> There is a minor fault about ACPI enumerated I2C devices with their modalias
> > >> attribute. Now modalias is set by device instance not by hardware ID.
> > >> For example "i2c:INTABCD:00", "i2c:INTABCD:01" etc.
> > >>
> > >> This means each device instance gets different modalias which does match
> > >> with generated modules.alias. Currently this is not problem as matching can
> > >> happen also with "acpi:INTABCD" modalias.
> > >>
> > > IMO, this is not the proper fix for the modalias problem because ACPI
> > > enumerated I2C device may have compatible ids.
> > > Instead, we should export all the compatible ids as the modules alias of
> > > the ACPI enumerated I2C device.
> > >
> > > can you please take a look at the patch I sent out earlier?
> > > https://patchwork.kernel.org/patch/3034991/
> > > https://patchwork.kernel.org/patch/3035041/
> > > https://patchwork.kernel.org/patch/3035021/
> > I see. This makes sense as it avoids that same device has two different 
> > modaliases from both acpi and other subsystem.
> > 
> > How about modalias nodes in sysfs, should they also reflect what is 
> > matching uvent?
> > 
> good catch, will fix "modalias" as well in next version.

Hi,

I have a question about the device "uevent" and "modalias" sysfs
attributes.
what is the relationship between these two?
Am I right to say that, if there is the "MODALIAS" field in uevent file,
this field must be consistent with the content in "modalias" attribute?

I checked the code in drivers/base/platform.c,
static ssize_t modalias_show(struct device *dev, struct device_attribute
*a,
                             char *buf)
{
        struct platform_device  *pdev = to_platform_device(dev);
        int len = snprintf(buf, PAGE_SIZE, "platform:%s\n", pdev->name);

        return (len >= PAGE_SIZE) ? (PAGE_SIZE - 1) : len;
}

static int platform_uevent(struct device *dev, struct kobj_uevent_env
*env)
{
        struct platform_device  *pdev = to_platform_device(dev);
        int rc;

        /* Some devices have extra OF data and an OF-style MODALIAS */
        rc = of_device_uevent_modalias(dev, env);
        if (rc != -ENODEV)
                return rc;

        add_uevent_var(env, "MODALIAS=%s%s", PLATFORM_MODULE_PREFIX,
                        pdev->name);
        return 0;
}

This means that the OF-style MODALIAS is not shown in "modalias" sysfs
attribute.
is this a bug?

thanks,
rui